User's Guide
SNOA487C – May 2007 – Revised May 2013
AN-1606 551012875, 551012922 Universal Op Amp
Evaluation Boards (SOT-23 and SC-70)
1
Overview
The 551012875 and 551012922 Universal Evaluation Boards are designed to aid in the evaluation and
testing of Texas Instruments low voltage/low power and some precision operational amplifiers. These
boards will accommodate op amps that are assembled in a 6-Pin or 5-Pin SOT-23 and SC-70 package,
regardless of the pin orientation.
This board is designed to use one or two amplifiers. Many different circuits can be made such as inverting,
non-inverting, and differential-IN-differential-OUT amplifiers and low-pass, high-pass, band-pass, bandreject, or notch second-order filters. The amplifiers can be powered with single or dual supplies. These
circuits can be configured without any modifications to the board; all that is necessary is to select the
correct resistors and capacitors. The other optional components can be left open or shorted depending on
the configuration desired.
These universal evaluation boards are designed as two-layer boards; the top side of each is designed for
op amps with a pinout as shown in Figure 1.
The bottom side of each board is designed for op amps with the pinout shown in Figure 2. The board has
been manufactured with vias connecting the equivalent pins of the top and bottom amplifiers. For
example, Pin 1 of IC1A is connected to Pin 3 of IC2A. Similarly all other equivalent pins of the top and
bottom amplifiers are connected. This allows for an efficient use of one board to test two amplifiers of
different package types while keeping the same components on the board; just make sure that only one
amplifier is soldered to the same pads.
Circuit performance of this evaluation board will be comparable to final production designs. Use this
evaluation board as a guide for general layout and a tool to aid in device testing and characterization.
SOT-23/SC-70
+IN
1
SOT-23/SC-70
6
+
V
OUT
+
V
5
- 2
V
SD
-
1
6
2
5
+
V
SD
+
-IN
3
4
OUT
Figure 1. Connection Diagram for IC1A and IC1B
+IN
3
4
-IN
Figure 2. Connection Diagram for IC2A and IC2B
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All other trademarks are the property of their respective owners.
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1
Hardware Setup
2
Hardware Setup
2.1
Component Notation
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The pins of the footprint for IC1A are connected to the equivalent pins for the footprint of IC2A and the same
is true for IC1B and IC2B Therefore, this application report will refer to the amplifier in IC1A or IC2A as Amp A
and the amplifier in IC1B or IC2B as Amp B. The subscript of the PCB component refers to the specific
amplifier; for example, R4A is used for Amp A and R4B for Amp B. In this document, components will be
referred to, as an example, C3. If using Amp A this refers to component C3A, if using Amp B this refers to
component C3B.
In some circuits, a resistor will be installed where the PCB is labeled for a capacitor or a capacitor will be
installed where a resistor is labeled. For example, CR6 indicates that a capacitor should be in the R6
position. RC5 means that a resistor will be installed in the C5 position.
2.2
Power
Power is applied to the points labeled V−, GND, and V+. If a single supply is used, then V− should be
connected to GND. A virtual ground, halfway between the positive supply voltage and ground, is the
reference point for the input and output voltages. The output voltage swings above and below this virtual
ground. Single-supply operation requires the generation of this virtual ground, usually at a voltage equal to
V+/2. The circuit in Figure 3 can be used to generate V+/2; R1 and R2 should be of equal values. This
junction along with capacitor C1 will form a low-pass filter used to eliminate conducted noise or transients
on the positive supply rail.
+
V
VIN
+
AMP
VOUT
-
+
V
R1
C1
R2
Figure 3. Single Supply Virtual Ground
2.3
Op Amp
Solder an op amp to either the IC1A or IC2A position. If building a circuit requiring two op amps, solder an
additional op amp to either IC1B or IC2B. The corresponding pinout is shown on each side of the PCB.
2.4
Bypassing
Install the following capacitors:
C6A, C9A, C6B, C9B: 0.1 µF
C7A, C8A, C7B, C8B: 1 µF
2.5
Shutdown
To use the shutdown feature of the amplifier in either the SOT-23 or the SC-70 package, install a resistor
at R15 and an optional capacitor at C11. The shutdown voltage is applied at S/D-A or S/D-B depending on
the package of the amplifier being used.
2
AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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SNOA487C – May 2007 – Revised May 2013
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Circuit Configurations
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2.6
Input and Output
SMA connectors are used for the input and output of signals. They are located on the edges of the PCB.
3
Circuit Configurations
3.1
Non-Inverting Amplifier
VIN
+
VOUT
-
R8
R12
R7
R14
C3, R4, R5 = 0 (SHORT)
C3
Short
R4
Short
R5
Short
R8
Input Termination
R7
Output series resistance (used for matching transmission lines or isolation)
R14
Gain Resistor
R12
Gain Resistor
Figure 4. Non-Inverting Amplifier
Where:
VOUT
VIN
=1+
R14
R12
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(1)
AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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Copyright © 2007–2013, Texas Instruments Incorporated
3
Circuit Configurations
3.2
www.ti.com
Inverting Amplifier
R6
R7
+
VOUT
VIN
R8
R11
R14
C3, R9, R13 = 0 (SHORT)
C3
Short
R9
Short
R13
Short
R8
Input Termination
R7
Output series resistance (used for matching transmission lines or isolation)
R14
Gain Resistor
R11
Gain Resistor
Figure 5. Inverting Amplifier
Where:
VOUT
VIN
3.3
=-
R14
R11
(2)
Register Calculations
Input Impedance: Set RT to the desired input impedance. Calculate R8 where:
R8 =
R11 x RT
R11 - RT
(3)
To cancel the input bias current set R6 to the value calculated with the following formula:
R6 =
3.4
R11 x R14
R11 - R14
(4)
Active Filter Applications
Both Sallen-Key and Multiple Feedback filters can be built on this PCB. To design a filter, use the
WEBENCH™ tool at www.ti.com. Performance at high frequencies is limited to the gain bandwidth product
of the amplifier, but within this frequency range, these active filters can achieve very good accuracy, if lowtolerance resistors and capacitor are used.
4
AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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Circuit Configurations
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3.5
Sallen-Key Low-Pass Filter
C3
Short
R13
Short
R7
Output series resistance (used for matching transmission lines or isolation)
R8
Input Termination
Set the following as determined using WEBENCH: R4, R5, CR6, R14, R12
C5
R4
R5
VIN
R7
+
CR6
R8
VOUT
-
R12
R14
C3, R13 = 0 (SHORT)
Figure 6. Sallen-Key Low-Pass Filter
3.6
Multiple Feedback Low-Pass Filter
Note: If needed, an input termination resistor will need to be soldered on to the SMA connector between
the signal pin and the ground pin.
R6
Short
R13
Short
R9
Short
C5
Short
R7
Output series resistance (used for matching transmission lines or isolation)
Set the following as determined using WEBENCH: RC3, CR8, R4, R11, C10
R4
C10
RC3
R11
-
VIN
RIN
R7
VOUT
CR8
+
R6, R13, R9, C5 = 0 (SHORT)
Figure 7. Multiple Feedback Low-Pass Filter
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5
Circuit Configurations
3.7
www.ti.com
Sallen-Key High-Pass Filter
C3
Short
R13
Short
R14
Short
R7
Output series resistance (used for matching transmission lines or isolation)
R8
Input Termination
Set as determined using WEBENCH: CR4, CR5, RC5, R6
RC5
CR4
CR5
VIN
R7
+
R6
R8
VOUT
-
R14 = 0
C3, R13, R14 = 0 (SHORT)
Figure 8. Sallen-Key High-Pass Filter
3.8
Multiple Feedback High-Pass Filter
Note: If needed, an input termination resistor will need to be soldered on to the SMA connector between
the signal pin and the ground pin.
R9
Short
R4
Short
R7
Output series resistance (used for matching transmission lines or isolation)
Set the following as determined using WEBENCH: C3, R8, C5, CR11, R14
C5
R14
C3
CR11
-
VIN
R7
VOUT
RIN
R8
+
R9, R4 = 0 (SHORT)
Figure 9. Multiple Feedback High-Pass Filter
6
AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
(SOT-23 and SC-70)
Copyright © 2007–2013, Texas Instruments Incorporated
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Circuit Configurations
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3.9
Sallen-Key Band-Pass Filter
C3
Short
R13
Short
R7
Output series resistance (used for matching transmission lines or isolation)
R8
Input Termination
Set as determined using WEBENCH: R4, C4, CR5, R6, RC5, R14, R12
RC5
R4
CR5
VIN
R8
R7
+
C4
R6
VOUT
-
R12
R14
C3, R13 = 0 (SHORT)
Figure 10. Sallen-Key Band-Pass Filter
3.10 Multiple Feedback Band-Pass Filter
Note: If needed, an input termination resistor will need to be soldered on to the SMA connector between
the signal pin and the ground pin.
R6
Short
R13
Short
R9
Short
R4
Short
R7
Output series resistance (used for matching transmission lines or isolation)
Set the following as determined using WEBENCH: RC3, R8, C5, CR11, R14
C5
R14
RC3
CR11
-
VIN
R7
VOUT
RIN
R8
+
R6, R13, R9, R4 = 0 (SHORT)
Figure 11. Multiple Feedback Band-Pass Filter
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7
Applications Using Two Amplifiers
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4
Applications Using Two Amplifiers
4.1
Two-Amplifier Filters
Filters using two amplifiers can be built by connecting the output of Amp A to the input of Amp B.
4.2
Single-Ended to Differential Conversion
The circuit in Figure 12 will convert a single-ended signal to a differential signal. This is done by using the
combination of an inverting amplifier and a non-inverting amplifier. Each amplifier generates output signals
of equal magnitude but of opposite polarity. This topology is useful in applications where the signal source
is single-ended, but the ADC requires a differential input. The board will need to be modified by
connecting Input A to Input B with a jumper wire.
R5A
+VIN
+
R8A
V
+VOUT
AMP
R12A
+
-
R7A
R6A
+
R1
R14A
R6B
C1
VDIFF
R2
RC4
+
-VOUT
AMP
-VIN
-
R7B
R11B
R14B
C3A, R4A, R5B, R9B, C3B = 0 (SHORT)
Figure 12. Single-Ended to Differential Conversion
8
AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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Applications Using Two Amplifiers
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4.3
Differential Input, Differential Output, Non-Inverting
Combining two non-inverting amplifiers with a common feedback network, as shown in Figure 13, forms a
non-inverting amplifier with a differential input and a differential output. Through the inherent cancellation
of the two op amp common-mode error signals this configuration fully exploits the noise reduction benefits
of CMRR. In addition the output voltage swing is doubled and depending on the op amp used, the
bandwidth and slew rate may also be increased, while maintaining the original gain bandwidth
specification.
+
V
CR4A
+VIN
R7A
+
+VOUT
AMP A
R8A
V
-
+
R6A
R1
R14A
C1
R3
R2
R14B
R6B
+
V
CR4B
-VIN
-
R7B
-VOUT
AMP B
+
R8B
C3A, R5A, R5B, C3B = 0 (SHORT)
A = 1+
R14A + R14B
R3
Figure 13. Differential Input, Differential Output, Non-Inverting
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AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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9
551012875-001 Schematic
5
www.ti.com
551012875-001 Schematic
Figure 14. 551012875-001 Schematic
10
AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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551012875-001 Layouts
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6
551012875-001 Layouts
Figure 15. 551012875-001 Top Layout
Figure 16. 551012875-001 Bottom Layout
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AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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11
551012922-001 Schematic
7
www.ti.com
551012922-001 Schematic
Figure 17. 551012922-001 Schematic
12
AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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551012922-001 Layouts
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8
551012922-001 Layouts
Figure 18. 551012922-001 Top Layout
Figure 19. 551012922-001 Bottom Layout
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AN-1606 551012875, 551012922 Universal Op Amp Evaluation Boards
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13
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