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OPA1611, OPA1612
SBOS450C – JULY 2009 – REVISED AUGUST 2014
OPA161x SoundPlus™ High-Performance, Bipolar-Input Audio Operational Amplifiers
1 Features
3 Description
•
•
•
The OPA1611 (single) and OPA1612 (dual) bipolarinput operational amplifiers achieve very low
1.1-nV/√Hz noise density with an ultralow distortion of
0.000015% at 1 kHz. The OPA1611 and OPA1612
offer rail-to-rail output swing to within 600 mV with a
2-kΩ load, which increases headroom and maximizes
dynamic range. These devices also have a high
output drive capability of ±30 mA.
1
•
•
•
•
•
•
•
•
Superior Sound Quality
Ultralow Noise: 1.1 nV/√Hz at 1 kHz
Ultralow Distortion:
0.000015% at 1 kHz
High Slew Rate: 27 V/μs
Wide Bandwidth: 40 MHz (G = +1)
High Open-Loop Gain: 130 dB
Unity Gain Stable
Low Quiescent Current:
3.6 mA per Channel
Rail-to-Rail Output
Wide Supply Range: ±2.25 V to ±18 V
Single and Dual Versions Available
These devices operate over a very wide supply range
of ±2.25 V to ±18 V, on only 3.6 mA of supply current
per channel. The OPA1611 and OPA1612 op amps
are unity-gain stable and provide excellent dynamic
behavior over a wide range of load conditions.
The dual version features completely independent
circuitry for lowest crosstalk and freedom from
interactions between channels, even when overdriven
or overloaded.
2 Applications
•
•
•
•
•
•
Both the OPA1611 and OPA1612 are available in
SOIC-8 packages and the OPA1612 is available in
SON-8. These devices are specified from –40°C to
+85°C.
Professional Audio Equipment
Microphone Preamplifiers
Analog and Digital Mixing Consoles
Broadcast Studio Equipment
Audio Test And Measurement
High-End A/V Receivers
Device Information(1)
PART NUMBER
OPA1611
OPA1612
PACKAGE
BODY SIZE (NOM)
SOIC (8)
4.90 mm × 3.91 mm
SOIC (8)
4.90 mm × 3.91 mm
SON (8)
3.00 mm × 3.00 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
space
space
THD+N Ratio vs Output Amplitude
Total Harmonic Distortion + Noise (%)
-80
1kHz Signal
BW = 80kHz
RSOURCE = 0W
-100
0.001
0.0001
0.00001
0.000001
0.01
-120
G = +1, RL = 600W
G = +1, RL = 2kW
G = -1, RL = 600W
G = -1, RL = 2kW
G = +10, RL = 600W
G = +10, RL = 2kW
0.1
-140
-160
1
10
Functional Block Diagram
V+
Total Harmonic Distortion + Noise (dB)
0.01
Pre-Output Driver
OUT
IN-
IN+
20
Output Amplitude (VRMS)
V-
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
OPA1611, OPA1612
SBOS450C – JULY 2009 – REVISED AUGUST 2014
www.ti.com
Table of Contents
1
2
3
4
5
6
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
6.1
6.2
6.3
6.4
6.5
7
1
1
1
2
3
4
Absolute Maximum Ratings ...................................... 4
Handling Ratings....................................................... 4
Recommended Operating Conditions....................... 4
Electrical Characteristics: VS = ±2.25 V to ±18 V .... 5
Typical Characteristics .............................................. 7
Detailed Description ............................................ 12
7.1 Overview ................................................................. 12
7.2 Functional Block Diagram ....................................... 12
7.3 Feature Description................................................. 12
8
Application and Implementation ........................ 15
8.1
8.2
8.3
8.4
8.5
Application Information............................................
Noise Performance .................................................
Total Harmonic Distortion Measurements...............
Capacitive Loads.....................................................
Application Circuit ...................................................
15
15
17
17
18
9 Power-Supply Recommendations...................... 19
10 Layout................................................................... 20
10.1 Layout Guidelines ................................................. 20
10.2 Layout Example .................................................... 20
11 Device and Documentation Support ................. 21
11.1
11.2
11.3
11.4
11.5
Documentation Support ........................................
Related Links ........................................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
21
21
21
21
21
12 Mechanical, Packaging, and Orderable
Information ........................................................... 21
4 Revision History
Changes from Revision B (July 2011) to Revision C
Page
•
Changed format to meet latest data sheet standards; added new sections, and moved existing sections........................... 1
•
Added SON-8 (DRG) package to data sheet ......................................................................................................................... 1
•
Changed SO to SOIC throughout document to match industry standard term...................................................................... 1
•
Added front-page curve .......................................................................................................................................................... 1
•
Added title to block diagram ................................................................................................................................................... 1
•
Deleted Package Information table; see package option addendum..................................................................................... 3
Changes from Revision A (August 2009) to Revision B
Page
•
Revised Features list items .................................................................................................................................................... 1
•
Updated front-page figure....................................................................................................................................................... 1
•
Added max specification for input voltage noise density at f = 1kHz .................................................................................... 5
•
Corrected typo in footnote 1 for Electrical Characteristics ..................................................................................................... 5
•
Revised Figure 4 .................................................................................................................................................................... 7
•
Updated Figure 7.................................................................................................................................................................... 7
•
Changed Figure 9 .................................................................................................................................................................. 7
•
Revised Figure 11 .................................................................................................................................................................. 7
•
Corrected typo in Figure 15 .................................................................................................................................................... 8
•
Updated Figure 29................................................................................................................................................................ 12
•
Revised fourth paragraph of Electrincal Overstress section ................................................................................................ 13
•
Revised table in Figure 34.................................................................................................................................................... 17
2
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Copyright © 2009–2014, Texas Instruments Incorporated
Product Folder Links: OPA1611 OPA1612
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SBOS450C – JULY 2009 – REVISED AUGUST 2014
5 Pin Configuration and Functions
D Package
OPA1611, SOIC-8
(Top View)
NC
(1)
D Package
OPA1612, SOIC-8
(Top View)
(1)
1
8
NC
-IN
2
7
V+
+IN
3
6
OUT
V-
4
5
NC
OUT A
-IN A
1
A
2
+IN A
3
V-
4
B
8
V+
7
OUT B
6
-IN B
5
+IN B
(1)
DRG Package
OPA1612, SON-8
(Top View)
8 V+
OUT A 1
-IN A 2
7 OUT B
A
+IN A 3
B
5 +IN B
V- 4
Pad
6 -IN B
(2)
(1) NC denotes no internal connection. Pin can be left floating or connected to any voltage between (V–) and (V+).
(2) Exposed thermal die pad on underside; connect thermal die pad to V–. Soldering the thermal pad improves heat dissipation and provides
specified performance.
Pin Functions
PIN
NAME
–IN
NO.
I/O
DESCRIPTION
—
I
Inverting input
D (OPA1611)
D (OPA1612)
DRG (OPA1612)
2
—
+IN
3
—
—
I
Noninverting input
–IN A
—
2
2
I
Inverting input, channel A
+IN A
—
3
3
I
Noninverting input, channel A
–IN B
—
6
6
I
Inverting input, channel B
+IN B
—
5
5
I
Noninverting input, channel B
NC
1, 5, 8
—
—
—
No internal connection
OUT
6
—
—
O
Output
OUT A
—
1
1
O
Output, channel A
OUT B
—
7
7
O
Output, channel B
V–
4
4
4
—
Negative (lowest) power supply
V+
7
8
8
—
Positive (highest) power supply
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SBOS450C – JULY 2009 – REVISED AUGUST 2014
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6 Specifications
6.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted) (1)
MIN
Supply voltage
VS = (V+) – (V–)
Input voltage
(V–) – 0.5
Input current (all pins except power-supply pins)
Output short-circuit (2)
(TA)
Junction temperature
(TJ)
(2)
UNIT
40
V
(V+) + 0.5
V
±10
mA
Continuous
Operating temperature
(1)
MAX
–55
+125
°C
200
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
Short-circuit to VS / 2 (ground in symmetrical dual supply setups), one amplifier per package.
6.2 Handling Ratings
Tstg
V(ESD)
(1)
(2)
MIN
MAX
UNIT
–65
+150
°C
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all
pins (1)
–3000
3000
Charged device model (CDM), per JEDEC specification
JESD22-C101, all pins (2)
–1000
1000
Machine model (MM)
–200
200
Storage temperature range
Electrostatic discharge
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
6.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
MIN
Supply voltage (V+ – V–)
Specified temperature
4
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NOM
MAX
UNIT
4.5 (±2.25)
36 (±18)
V
–40
+85
°C
Copyright © 2009–2014, Texas Instruments Incorporated
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6.4
SBOS450C – JULY 2009 – REVISED AUGUST 2014
Electrical Characteristics: VS = ±2.25 V to ±18 V
At TA = +25°C and RL = 2 kΩ, unless otherwise noted. VCM = VOUT = midsupply, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
AUDIO PERFORMANCE
THD+N
IMD
Total harmonic distortion + noise
Intermodulation distortion
0.000015%
G = +1, f = 1 kHz, VO = 3 VRMS
–136
SMPTE/DIN two-tone, 4:1 (60 Hz and 7 kHz),
G = +1, VO = 3 VRMS
0.000015%
DIM 30 (3-kHz square wave and 15-kHz sine
wave), G = +1, VO = 3 VRMS
0.000012%
CCIF twin-tone (19 kHz and 20 kHz), G = +1,
VO = 3 VRMS
0.000008%
dB
–136
dB
–138
dB
–142
dB
FREQUENCY RESPONSE
G = 100
80
MHz
G=1
40
MHz
Slew rate
G = –1
27
V/μs
Full-power bandwidth (1)
VO = 1 VPP
4
MHz
Overload recovery time
G = –10
500
ns
Channel separation (dual)
f = 1 kHz
–130
dB
Input voltage noise
f = 20 Hz to 20 kHz
GBW
Gain-bandwidth product
SR
NOISE
Input voltage noise density (2)
en
In
Input current noise density
μVPP
1.2
f = 10 Hz
2
nV/√Hz
f = 100 Hz
1.5
f = 1 kHz
1.1
nV/√Hz
f = 10 Hz
3
pA/√Hz
f = 1 kHz
1.7
pA/√Hz
1.5
nV/√Hz
OFFSET VOLTAGE
VOS
Input offset voltage
VS = ±15 V
dVOS/dT
VOS over temperature (2)
TA = –40°C to +85°C
PSRR
Power-supply rejection ratio
μV
±100
±500
1
4
μV/°C
VS = ±2.25 V to ±18 V
0.1
1
μV/V
VCM = 0 V
±60
±250
nA
VCM = 0 V, DRG package only
±60
±300
nA
350
nA
±25
±175
nA
INPUT BIAS CURRENT
IB
Input bias current
IB over temperature
IOS
(2)
Input offset current
TA = –40°C to +85°C
VCM = 0 V
INPUT VOLTAGE RANGE
VCM
Common-mode voltage range
CMRR
Common-mode rejection ratio
(V–) + 2
(V–) + 2 V ≤ VCM ≤ (V+) – 2 V
110
(V+) – 2
V
120
dB
INPUT IMPEDANCE
(1)
(2)
Differential
20k || 8
Ω || pF
Common-mode
109 || 2
Ω || pF
Full-power bandwidth = SR / (2π × VP), where SR = slew rate.
Specified by design and characterization.
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Electrical Characteristics: VS = ±2.25 V to ±18 V (continued)
At TA = +25°C and RL = 2 kΩ, unless otherwise noted. VCM = VOUT = midsupply, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
(V–) + 0.2 V ≤ VO ≤ (V+) – 0.2 V, RL = 10 kΩ
114
130
dB
(V–) + 0.6 V ≤ VO ≤ (V+) – 0.6 V, RL = 2 kΩ
110
114
dB
OPEN-LOOP GAIN
AOL
Open-loop voltage gain
OUTPUT
RL = 10 kΩ, AOL ≥ 114 dB
(V–) + 0.2
(V+) – 0.2
RL = 2 kΩ, AOL ≥ 110 dB
(V–) + 0.6
(V+) – 0.6
V
VOUT
Voltage output
IOUT
Output current
See Figure 27
mA
ZO
Open-loop output impedance
See Figure 28
Ω
ISC
Short-circuit current
CLOAD
Capacitive load drive
V
+55
mA
–62
mA
See Typical Characteristics
pF
POWER SUPPLY
VS
Specified voltage
IQ
Quiescent current (per channel)
IOUT = 0 A
±2.25
IQ over Temperature (3)
TA = –40°C to +85°C
3.6
±18
V
4.5
mA
5.5
mA
°C
TEMPERATURE RANGE
θ JA
(3)
6
Specified range
–40
+85
Operating range
–55
+125
Thermal resistance, SOIC-8
150
°C
°C/W
Specified by design and characterization.
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SBOS450C – JULY 2009 – REVISED AUGUST 2014
6.5 Typical Characteristics
At TA = +25°C, VS = ±15 V, and RL = 2 kΩ, unless otherwise noted.
20nV/div
Voltage Noise Density (nV/ÖHz)
Current Noise Density (pA/ÖHz)
100
Voltage Noise Density
10
Current Noise Density
1
0.1
1
10
100
1k
10k
100k
Time (1s/div)
Frequency (Hz)
Figure 2. 0.1-Hz to 10-Hz Noise
30
10k
Maximum output
voltage range
without slew-rate
induced distortion
VS = ±15V
25
EO
1k
Output Voltage (VPP)
Voltage Noise Spectral Density, EO (nV/?Hz)
Figure 1. Input Voltage Noise Density and Input Current
Noise Density vs Frequency
Total Output
Voltage Noise
RS
100
Resistor
Noise
10
20
15
VS = ±5V
10
VS = ±2.25V
5
2
EO =
1
100
1k
10k
2
2
en + (in RS) + 4kTRS
100k
0
10k
1M
100k
140
180
25
120
160
20
140
15
Gain (dB)
120
60
100
40
80
60
Phase
Phase (degrees)
80
-5
-10
-15
-20
20
-20
100
1k
10k
100k
1M
10M
G = +1
0
40
0
100M
G = -1
5
0
-40
G = +10
10
Gain (dB)
Gain
20
10M
Figure 4. Maximum Output Voltage vs Frequency
Figure 3. Voltage Noise vs Source Resistance
100
1M
Frequency (Hz)
Source Resistance, RS (W)
-25
100k
1M
Frequency (Hz)
10M
100M
Frequency (Hz)
Figure 5. Gain and Phase vs Frequency
Figure 6. Closed-Loop Gain vs Frequency
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Typical Characteristics (continued)
At TA = +25°C, VS = ±15 V, and RL = 2 kΩ, unless otherwise noted.
VOUT = 3VRMS
BW = 80kHz
0.00001
10
100
1k
0.01
Total Harmonic Distortion + Noise (%)
Total Harmonic Distortion + Noise (%)
G = -1, RL = 2kW
G = +10, RL = 600W
G = +10, RL = 2kW
-140
RSOURCE OPA1611
-15V
0.001
RL
RSOURCE = 600W
0.0001
RSOURCE = 150W
100
1k
Frequency (Hz)
0.01
Total Harmonic Distortion + Noise (%)
Total Harmonic Distortion + Noise (%)
VOUT = 3VRMS
BW > 500kHz
-140
100k
10k
RSOURCE OPA1611
-15V
0.001
-120
0.0001
10
100
-140
-160
1
10
20
Intermodulation Distortion (%)
Total Harmonic Distortion + Noise (%)
-120
0.01
-80
SMPTE/DIN
Two-Tone
4:1 (60Hz and 7kHz)
0.001
-100
DIM30
(3kHz square wave
and 15kHz sine wave)
0.0001
-120
-140
0.00001
CCIF Twin-Tone
(19kHz and 20kHz)
-160
0.000001
0.1
1
10
20
Output Amplitude (VRMS)
Figure 11. THD+N Ratio vs Output Amplitude
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-140
100k
10k
G = +1
Output Amplitude (VRMS)
8
1k
Intermodulation Distortion (dB)
-100
Total Harmonic Distortion + Noise (dB)
-80
G = +1, RL = 600W
G = +1, RL = 2kW
G = -1, RL = 600W
G = -1, RL = 2kW
G = +10, RL = 600W
G = +10, RL = 2kW
0.1
RSOURCE = 150W
RSOURCE = 0W
0.00001
Figure 10. THD+N Ratio vs Frequency
0.001
0.000001
0.01
-100
RSOURCE = 600W
Frequency (Hz)
1kHz Signal
BW = 80kHz
RSOURCE = 0W
0.00001
RL
RSOURCE = 300W
Figure 9. THD+N Ratio vs Frequency
0.0001
-80
VOUT = 3VRMS
BW > 500kHz
+15V
Frequency (Hz)
0.01
20k
Total Harmonic Distortion + Noise (dB)
-120
0.0001
Total Harmonic Distortion + Noise (dB)
-100
G = -1, RL = 2kW
G = +11, RL = 600W
G = +11, RL = 2kW
1k
10k
Figure 8. THD+N Ratio vs Frequency
0.001
100
-120
-140
20
Figure 7. THD+N Ratio vs Frequency
10
RSOURCE = 300W
0.00001
10k 20k
0.00001
-100
RSOURCE = 0W
Frequency (Hz)
G = +1, RL = 600W
G = +1, RL = 2kW
G = -1, RL = 600W
-80
VOUT = 3VRMS
BW = 80kHz
+15V
Total Harmonic Distortion + Noise (dB)
-120
G = +1, RL = 600W
G = +1, RL = 2kW
G = -1, RL = 600W
Total Harmonic Distortion + Noise (dB)
0.0001
Figure 12. Intermodulation Distortion vs Output Amplitude
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SBOS450C – JULY 2009 – REVISED AUGUST 2014
Typical Characteristics (continued)
At TA = +25°C, VS = ±15 V, and RL = 2 kΩ, unless otherwise noted.
-100
160
VS = ±15V
VOUT = 3.5VRMS
G = +1
RL = 600W
-110
-120
-130
-140
RL = 2kW
-150
-160
RL = 5kW
-170
Power-Supply Rejection Ratio (dB)
Channel Separation (dB)
-90
Common-Mode Rejection Ratio (dB)
-80
140
-PSRR
120
+PSRR
100
CMRR
80
60
40
20
-180
0
100
10
1k
10k
100k
1
10
100
1k
Frequency (Hz)
10k
100k
Figure 13. Channel Separation vs Frequency
100M
G = -1
CL = 50pF
CF
20mV/div
20mV/div
10M
Figure 14. CMRR and PSRR vs Frequency
(Referred to Input)
G = +1
CL = 50pF
+15V
OPA1611
-15V
1M
Frequency (Hz)
RI
= 2kW
RF
= 5.6pF
= 2kW
+15V
RL
CL
OPA1611
CL
-15V
Time (0.1ms/div)
Time (0.1ms/div)
Figure 15. Small-Signal Step Response (100 mV)
Figure 16. Small-Signal Step Response (100 mV)
G = +1
CL = 50pF
RL = 2kW
G = -1
CL = 50pF
RL = 2kW
RF = 75W
2V/div
2V/div
RF = 0W
See Applications Information,
Input Protection section
Time (0.5ms/div)
Time (0.5ms/div)
Figure 17. Large-Signal Step Response
Figure 18. Large-Signal Step Response
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Typical Characteristics (continued)
At TA = +25°C, VS = ±15 V, and RL = 2 kΩ, unless otherwise noted.
25
50
CF = 5.6pF
RS = 0W
RS
40
RS = 25W
RL
-15V
RS = 25W
30
CL
20
RS = 50W
10
0
RS
15
CL
-15V
10
RS = 50W
G = -1
0
100
200
300
400
500
+15V
OPA1611
5
G = +1
0
RF = 2kW
RI = 2kW
20
OPA1611
Overshoot (%)
Overshoot (%)
RS = 0W
+15V
0
600
100 200 300 400 500 600 700 800 900 1000
Capacitive Load (pF)
Capacitive Load (pF)
Figure 19. Small-Signal Overshoot vs Capacitive Load
(100-mV Output Step)
Figure 20. Small-Signal Overshoot vs Capacitive Load
(100-mV Output Step)
120
1.0
0.8
100
IB and IOS Current (nA)
0.6
AOL (mV/V)
0.4
0.2
10kW
0
-0.2
-0.4
2kW
-0.6
-IB
80
60
+IB
40
IOS
20
-0.8
-1.0
-40
0
10
-15
35
60
-40
85
-15
70
VS = ±18V
+IB
85
4.5
50
4.0
40
30
IQ (mA)
IB and IOS (nA)
50
5.0
60
IOS
20
3.5
3.0
10
-IB
0
2.5
Common-Mode Range
-10
2.0
-20
-18
-12
-6
0
6
12
18
-40
-15
Common-Mode Voltage (V)
Figure 23. IB and IOS vs Common-Mode Voltage
10
35
Figure 22. IB and IOS vs Temperature
Figure 21. Open-Loop Gain vs Temperature
80
10
Temperature (°C)
Temperature (°C)
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10
35
60
85
Temperature (°C)
Figure 24. Quiescent Current vs Temperature
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Typical Characteristics (continued)
At TA = +25°C, VS = ±15 V, and RL = 2 kΩ, unless otherwise noted.
4.0
75
3.9
70
3.8
65
60
3.6
ISC (mA)
IQ (mA)
3.7
-ISC
3.5
3.4
55
+ISC
50
45
3.3
40
3,2
35
Specified Supply-Voltage Range
3.1
3.0
30
0
4
8
12
16
20
24
28
32
36
-50
-25
0
Supply Voltage (V)
14
1k
VS = ±15V
Dual version with
both channels
driven simultaneously
-13
50
75
100
125
Figure 26. Short-Circuit Current vs Temperature
10k
+25°C
ZO (W)
Output Voltage (V)
Figure 25. Quiescent Current vs Supply Voltage
15
13
25
Temperature (°C)
+85°C
-40°C
100
10
1
-14
0.1
-15
0
10
20
30
40
50
10
100
1k
10k
100k
1M
10M
100M
Output Current (mA)
Frequency (Hz)
Figure 27. Output Voltage vs Output Current
Figure 28. Open-Loop Output Impedance vs Frequency
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7 Detailed Description
7.1 Overview
The OPA161x family of bipolar-input operational amplifiers achieve very low 1.1-nV/√Hz noise density with
an ultralow distortion of 0.000015% at 1 kHz. The rail-to-rail output swing, within 600 mV with a 2-kΩ load,
increases headroom and maximizes dynamic range. These devices also have a high output drive capability
of ±40 mA. The wide supply range of ±2.25 V to ±18 V, on only 3.6 mA of supply current per channel, makes
them applicable to both 5V systems and 36V audio applications. The OPA1611 and OPA1612 op amps are
unity-gain stable and provide excellent dynamic behavior over a wide range of load conditions.
7.2 Functional Block Diagram
V+
Pre-Output Driver
OUT
IN-
IN+
V-
Figure 29. OPA1611 Simplified Schematic
7.3 Feature Description
7.3.1 Power Dissipation
The OPA1611 and OPA1612 series op amps are capable of driving 2-kΩ loads with a power-supply voltage up
to ±18 V. Internal power dissipation increases when operating at high supply voltages. Copper leadframe
construction used in the OPA1611 and OPA1612 series op amps improves heat dissipation compared to
conventional materials. Circuit board layout can also help minimize junction temperature rise. Wide copper traces
help dissipate the heat by acting as an additional heat sink. Temperature rise can be further minimized by
soldering the devices to the circuit board rather than using a socket.
7.3.2 Electrical Overstress
Designers often ask questions about the capability of an operational amplifier to withstand electrical overstress.
These questions tend to focus on the device inputs, but may involve the supply voltage pins or even the output
pin. Each of these different pin functions have electrical stress limits determined by the voltage breakdown
characteristics of the particular semiconductor fabrication process and specific circuits connected to the pin.
Additionally, internal electrostatic discharge (ESD) protection is built into these circuits to protect them from
accidental ESD events both before and during product assembly.
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Feature Description (continued)
Having a good understanding of this basic ESD circuitry and its relevance to an electrical overstress event is
helpful. Figure 30 shows the ESD circuits contained in the OPA161x series (indicated by the dashed line area).
The ESD protection circuitry involves several current-steering diodes connected from the input and output pins
and routed back to the internal power-supply lines, where they meet at an absorption device internal to the
operational amplifier. This protection circuitry is intended to remain inactive during normal circuit operation.
RF
+V
+VS
OPA1611
RI
ESD CurrentSteering Diodes
-In
Op-Amp
Core
+In
Edge-Triggered ESD
Absorption Circuit
ID
VIN
Out
RL
(1)
-V
-VS
(1) VIN = +VS + 500 mV.
Figure 30. Equivalent Internal ESD Circuitry and its Relation to a Typical Circuit Application
An ESD event produces a short duration, high-voltage pulse that is transformed into a short duration, highcurrent pulse when discharged through a semiconductor device. The ESD protection circuits are designed to
provide a current path around the operational amplifier core to prevent damage to the core. The energy absorbed
by the protection circuitry is then dissipated as heat.
When an ESD voltage develops across two or more of the amplifier device pins, current flows through one or
more of the steering diodes. Depending on the path that the current takes, the absorption device may activate.
The absorption device internal to the OPA1611 triggers when a fast ESD voltage pulse is impressed across the
supply pins. Once triggered, the absorption device quickly activates and clamps the ESD pulse to a safe voltage
level.
When the operational amplifier connects into a circuit such as the one Figure 30 shows, the ESD protection
components are intended to remain inactive and not become involved in the application circuit operation.
However, circumstances may arise where an applied voltage exceeds the operating voltage range of a given pin.
If this condition occurs, some of the internal ESD protection circuits may possibly be biased on, and conduct
current. Any such current flow occurs through steering diode paths and rarely involves the absorption device.
Figure 30 shows a specific example where the input voltage, VIN, exceeds the positive supply voltage (+VS) by
500 mV or more. Much of what happens in the circuit depends on the supply characteristics. If +VS can sink the
current, one of the upper input steering diodes conducts and directs current to +VS. Excessively high current
levels can flow with increasingly higher VIN. As a result, the datasheet specifications recommend that applications
limit the input current to 10 mA.
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Feature Description (continued)
If the supply is not capable of sinking the current, VIN may begin sourcing current to the operational amplifier, and
then take over as the source of positive supply voltage. The danger in this case is that the voltage can rise to
levels that exceed the operational amplifier absolute maximum ratings. In extreme but rare cases, the absorption
device triggers on while +VS and –VS are applied. If this event happens, a direct current path is established
between the +VS and –VS supplies. The power dissipation of the absorption device is quickly exceeded, and the
extreme internal heating destroys the operational amplifier.
Another common question involves what happens to the amplifier if an input signal is applied to the input while
the power supplies +VS or –VS are at 0 V. Again, the result depends on the supply characteristic while at 0 V, or
at a level below the input signal amplitude. If the supplies appear as high impedance, then the operational
amplifier supply current may be supplied by the input source via the current steering diodes. This state is not a
normal bias condition; the amplifier most likely does not operate normally. If the supplies are low impedance,
then the current through the steering diodes can become quite high. The current level depends on the ability of
the input source to deliver current, and any resistance in the input path.
If there is an uncertainty about the ability of the supply to absorb this current, external zener diodes may be
added to the supply pins; see Figure 30. The zener voltage must be selected such that the diode does not turn
on during normal operation. However, the zener diode voltage must be low enough so that the zener diode
conducts if the supply pin begins to rise above the safe operating supply voltage level.
7.3.3 Operating Voltage
The OPA161x series op amps operate from ±2.25-V to ±18-V supplies while maintaining excellent performance.
The OPA161x series can operate with as little as +4.5 V between the supplies and with up to +36 V between the
supplies. However, some applications do not require equal positive and negative output voltage swing. With the
OPA161x series, power-supply voltages do not need to be equal. For example, the positive supply could be set
to +25 V with the negative supply at –5 V.
In all cases, the common-mode voltage must be maintained within the specified range. In addition, key
parameters are assured over the specified temperature range of TA = –40°C to +85°C. Parameters that vary with
operating voltage or temperature are shown in the Typical Characteristics.
7.3.4 Input Protection
The input terminals of the OPA1611 and the OPA1612 are protected from excessive differential voltage with
back-to-back diodes, as Figure 31 shows. In most circuit applications, the input protection circuitry has no
consequence. However, in low-gain or G = +1 circuits, fast ramping input signals can forward bias these diodes
because the output of the amplifier cannot respond rapidly enough to the input ramp. This effect is illustrated in
Figure 17 of the Typical Characteristics. If the input signal is fast enough to create this forward bias condition, the
input signal current must be limited to 10 mA or less. If the input signal current is not inherently limited, an input
series resistor (RI) or a feedback resistor (RF) can be used to limit the signal input current. This input series
resistor degrades the low-noise performance of the OPA1611 and is examined in the Noise Performance section.
Figure 31 shows an example configuration when both current-limiting input and feedback resistors are used.
RF
-
OPA1611
RI
Input
Output
+
Figure 31. Pulsed Operation
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8 Application and Implementation
8.1 Application Information
The OPA1611 and OPA1612 are unity-gain stable, precision op amps with very low noise; these devices are also
free from output phase reversal. Applications with noisy or high-impedance power supplies require decoupling
capacitors close to the device power-supply pins. In most cases, 0.1-μF capacitors are adequate.
8.2 Noise Performance
Figure 32 shows the total circuit noise for varying source impedances with the op amp in a unity-gain
configuration (no feedback resistor network, and therefore no additional noise contributions).
The OPA1611 (GBW = 40 MHz, G = +1) is shown with total circuit noise calculated. The op amp itself
contributes both a voltage noise component and a current noise component. The voltage noise is commonly
modeled as a time-varying component of the offset voltage. The current noise is modeled as the time-varying
component of the input bias current and reacts with the source resistance to create a voltage component of
noise. Therefore, the lowest noise op amp for a given application depends on the source impedance. For low
source impedance, current noise is negligible, and voltage noise generally dominates. The low voltage noise of
the OPA161x series op amps makes them a good choice for use in applications where the source impedance is
less than 1 kΩ.
8.2.1 Detailed Design Procedure
The equation in Figure 32 shows the calculation of the total circuit noise, with these parameters:
• en = voltage noise
• In = current noise
• RS = source impedance
• k = Boltzmann’s constant = 1.38 × 10–23 J/K
• T = temperature in degrees Kelvin (K)
8.2.2 Application Curve
Voltage Noise Spectral Density, EO (nV/?Hz)
VOLTAGE NOISE SPECTRAL DENSITY
vs SOURCE RESISTANCE
10k
EO
1k
Total Output
Voltage Noise
RS
100
Resistor
Noise
10
2
2
2
EO = en + (in RS) + 4kTRS
1
100
1k
10k
100k
1M
Source Resistance, RS (W)
Figure 32. Noise Performance of the OPA1611 In Unity-Gain Buffer Configuration
8.2.3 Basic Noise Calculations
Design of low-noise op amp circuits requires careful consideration of a variety of possible noise contributors:
noise from the signal source, noise generated in the op amp, and noise from the feedback network resistors. The
total noise of the circuit is the root-sum-square combination of all noise components.
The resistive portion of the source impedance produces thermal noise proportional to the square root of the
resistance. Figure 32 plots this function. The source impedance is usually fixed; consequently, select the op amp
and the feedback resistors to minimize the respective contributions to the total noise.
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Noise Performance (continued)
Figure 33 shows both inverting and noninverting op amp circuit configurations with gain. In circuit configurations
with gain, the feedback network resistors also contribute noise.
The current noise of the op amp reacts with the feedback resistors to create additional noise components. The
feedback resistor values can generally be chosen to make these noise sources negligible. The equations for total
noise are shown for both configurations.
Noise in Noninverting Gain Configuration
Noise at the output:
R2
2
2
R1
EO = 1 +
R2
R1
2
2
2
2
2
2
en + e1 + e2 + (inR2) + eS + (inRS)
EO
R2
Where eS = Ö4kTRS ´ 1 +
R1
2
1+
R2
R1
= thermal noise of RS
RS
R2
e1 = Ö4kTR1 ´
R1
VS
= thermal noise of R1
e2 = Ö4kTR2 = thermal noise of R2
Noise in Inverting Gain Configuration
Noise at the output:
R2
2
2
EO
R1
= 1+
R2
R1 + RS
2
EO
RS
Where eS = Ö4kTRS ´
2
2
2
2
en + e1 + e2 + (inR2) + eS
R2
R1 + RS
= thermal noise of RS
VS
e1 = Ö4kTR1 ´
R2
R1 + RS
= thermal noise of R1
e2 = Ö4kTR2 = thermal noise of R2
For the OPA161x series op amps at 1 kHz, en = 1.1 nV/√Hz and in = 1.7 pA/√Hz.
Figure 33. Noise Calculation in Gain Configurations
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8.3 Total Harmonic Distortion Measurements
The OPA161x series op amps have excellent distortion characteristics. THD + noise is below 0.00008% (G = +1,
VO = 3 VRMS, BW = 80 kHz) throughout the audio frequency range, 20 Hz to 20 kHz, with a 2-kΩ load (see
Figure 7 for characteristic performance).
The distortion produced by OPA1611 series op amps is below the measurement limit of many commercially
available distortion analyzers. However, a special test circuit (such as Figure 34 shows) can be used to extend
the measurement capabilities.
Op amp distortion can be considered an internal error source that can be referred to the input. Figure 34 shows a
circuit that causes the op amp distortion to be 101 times (or approximately 40 dB) greater than that normally
produced by the op amp. The addition of R3 to the otherwise standard noninverting amplifier configuration alters
the feedback factor or noise gain of the circuit. The closed-loop gain is unchanged, but the feedback available for
error correction is reduced by a factor of 101, thus extending the resolution by 101. Note that the input signal and
load applied to the op amp are the same as with conventional feedback without R3. Keep the value of R3 small to
minimize its effect on the distortion measurements.
Validity of this technique can be verified by duplicating measurements at high gain and/or high frequency where
the distortion is within the measurement capability of the test equipment. Measurements for this data sheet were
made with an audio precision system two distortion and noise analyzer, which greatly simplifies such repetitive
measurements. The measurement technique can, however, be performed with manual distortion measurement
instruments.
R1
R2
SIG. DIST.
GAIN GAIN
R3
Signal Gain = 1+
VO = 3VRMS
OPA1611
R2
R1
R2
Distortion Gain = 1+
R1 II R3
Generator
Output
1
101
R1
R2
R3
¥
1kW
10W
-1
101
4.99kW 4.99kW 49.9W
+10
110
549W 4.99kW 49.9W
Analyzer
Input
Audio Precision
System Two(1)
with PC Controller
Load
(1) For measurement bandwidth, see Figure 7 through Figure 12.
Figure 34. Distortion Test Circuit
8.4 Capacitive Loads
The dynamic characteristics of the OPA1611 and OPA1612 have been optimized for commonly encountered
gains, loads, and operating conditions. The combination of low closed-loop gain and high capacitive loads
decreases the phase margin of the amplifier and can lead to gain peaking or oscillations. As a result, heavier
capacitive loads must be isolated from the output. The simplest way to achieve this isolation is to add a small
resistor (RS equal to 50 Ω, for example) in series with the output.
This small series resistor also prevents excess power dissipation if the output of the device becomes shorted.
Figure 19 and Figure 20 illustrate graphs of Small-Signal Overshoot vs Capacitive Load for several values of RS.
Also, refer to Applications Bulletin AB-028, Feedback Plots Define Op Amp AC Performance (SBOA015),
available for download from the TI web site, for details of analysis techniques and application circuits.
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8.5 Application Circuit
Figure 35 shows how to use the OPA1611 as an amplifier for professional audio headphones. The circuit shows
the left side stereo channel. An identical circuit is used to drive the right side stereo channel.
820W
2200pF
0.1mF
+VA
(+15V)
330W
IOUTL+
OPA1611
2700pF
-VA
(-15V)
680W
620W
Audio DAC
with Differential
Current
Outputs
0.1mF
+VA
(+15V)
0.1mF
100W
820W
OPA1611
8200pF
2200pF
-VA
(-15V)
0.1mF
0.1mF
+VA
(+15V)
L Ch
Output
680W
620W
IOUTLOPA1611
330W
2700pF
-VA
(-15V)
0.1mF
Figure 35. Audio DAC Post Filter (I/V Converter and Low-Pass Filter)
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9 Power-Supply Recommendations
The OPA161x is specified for operation from 4.5 V to 36 V (±2.25 V to ±18 V); many specifications apply from
–40°C to +85°C. Parameters that can exhibit significant variance with regard to operating voltage or temperature
are presented in the Typical Characteristics section.
CAUTION
Supply voltages larger than 40 V can permanently damage the device; see the
Absolute Maximum Ratings.
Place 0.1-μF bypass capacitors close to the power-supply pins to reduce errors coupling in from noisy or highimpedance power supplies. For more detailed information on bypass capacitor placement, refer to the Typical
Characteristics section.
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10 Layout
10.1 Layout Guidelines
For best operational performance of the device, use good printed circuit board (PCB) layout practices, including:
• Noise can propagate into analog circuitry through the power pins of the circuit as a whole and the op amp
itself. Bypass capacitors are used to reduce the coupled noise by providing low-impedance power sources
local to the analog circuitry.
– Connect low-ESR, 0.1-µF ceramic bypass capacitors between each supply pin and ground, placed as
close to the device as possible. A single bypass capacitor from V+ to ground is applicable for singlesupply applications.
• Separate grounding for analog and digital portions of the circuitry is one of the simplest and most-effective
methods of noise suppression. One or more layers on multilayer PCBs are usually devoted to ground planes.
A ground plane helps distribute heat and reduces EMI noise pickup. Make sure to physically separate digital
and analog grounds while paying attention to the flow of the ground current. For more detailed information,
refer to the application report Circuit Board Layout Techniques (SLOA089).
• In order to reduce parasitic coupling, run the input traces as far away from the supply or output traces as
possible. If these traces cannot be keep them separate, crossing the sensitive trace perpendicular as
opposed to in parallel with the noisy trace is the preferred method.
• Place the external components as close to the device as possible. As shown in Figure 36, keeping RF and
RG close to the inverting input minimizes parasitic capacitance.
• Keep the length of input traces as short as possible. Always remember that the input traces are the most
sensitive part of the circuit.
• Consider a driven, low-impedance guard ring around the critical traces. A guard ring can significantly reduce
leakage currents from nearby traces that are at different potentials.
10.2 Layout Example
RIN
+
VIN
VOUT
RG
RF
(Schematic Representation)
Run the input traces
as far away from
the supply lines
as possible
Place components
close to device and to
each other to reduce
parasitic errors
VS+
RF
NC
NC
±IN
V+
+IN
OUT
V±
NC
RG
GND
VIN
GND
RIN
Only needed for
dual-supply
operation
GND
VS±
(or GND for single supply)
Use low-ESR, ceramic
bypass capacitor
VOUT
Ground (GND) plane on another layer
Figure 36. Operational Amplifier Board Layout for a Noninverting Configuration
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11 Device and Documentation Support
11.1 Documentation Support
11.1.1 Related Documentation
For related documentation see the following:
• Feedback Plots Define Op Amp AC Performance , SBOA015
• Circuit Board Layout Techniques, SLOA089
11.2 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to sample or buy.
Table 1. Related Links
PARTS
PRODUCT FOLDER
SAMPLE & BUY
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
OPA1611
Click here
Click here
Click here
Click here
Click here
OPA1612
Click here
Click here
Click here
Click here
Click here
11.3 Trademarks
SoundPlus is a trademark of Texas Instruments, Inc.
All other trademarks are the property of their respective owners.
11.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
11.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
12 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
OPA1611AID
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
OPA
1611A
OPA1611AIDR
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
OPA
1611A
OPA1612AID
ACTIVE
SOIC
D
8
75
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
OPA
1612A
OPA1612AIDR
ACTIVE
SOIC
D
8
2500
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
OPA
1612A
OPA1612AIDRGR
ACTIVE
SON
DRG
8
3000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
OVII
OPA1612AIDRGT
ACTIVE
SON
DRG
8
250
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
OVII
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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