Texas Instruments DIYAMP-SOT23-EVM User manual

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DIYAMP-SOT23-EVM
User's Guide
SBOU191–July 2017
DIYAMP-SOT23-EVM
This user's guide contains support documentation for the DIYAMP-SOT23 evaluation module (EVM).
Included is a description of how to set up and configure the EVM, printed circuit board (PCB) layout,
schematic, and bill of materials (BOM) of the DIYAMP-SOT23-EVM.
Contents
1 Introduction ................................................................................................................... 3
2 Hardware Setup.............................................................................................................. 4
3 Schematic and PCB Layout ................................................................................................ 7
4 Connections................................................................................................................. 27
5 Bill of Materials and Reference........................................................................................... 30
List of Figures
1 Location of Circuit Configurations ......................................................................................... 4
2 Detach Desired Circuit Configuration ..................................................................................... 5
3 Detach Configuration With Attached IC and Passive Components................................................... 5
4 Terminal Strip (TS-132-G-AA) Broken Into 4-Pin Lengths ............................................................. 5
5 4-Pin Length Terminal Strips Inserted in DIP Socket................................................................... 6
6 Detached Board Configuration Position Over Terminal Pins .......................................................... 6
7 Fully-Assembled Circuit Configuration From DIYAMP-SOT23-EVM.................................................. 6
8 Silk Screen Circuit Schematic.............................................................................................. 7
9 Single-Supply, Multiple Feedback Filter Schematic..................................................................... 7
10 Single-Supply, MFB Filter Top Layer ..................................................................................... 8
11 Single-Supply, MFB Filter Bottom Layer.................................................................................. 8
12 Single-Supply, Sallen-Key Filter Schematic.............................................................................. 9
13 Single-Supply, Sallen-Key Filter Top Layer .............................................................................. 9
14 Single-Supply, Sallen-Key Filter Bottom Layer......................................................................... 10

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15 Single-Supply, Non-Inverting Amplifier Schematic..................................................................... 10
16 Single-Supply, Non-Inverting Amplifier Top Layer..................................................................... 12
17 Single-Supply, Non-Inverting Amplifier Bottom Layer................................................................. 12
18 Single-Supply, Inverting Amplifier Schematic .......................................................................... 12
19 Single-Supply, Inverting Amplifier Top Layer........................................................................... 13
20 Single-Supply, Inverting Amplifier Bottom Layer....................................................................... 14
21 Difference Amplifier Schematic........................................................................................... 14
22 Difference Amplifier Top Layer........................................................................................... 15
23 Difference Amplifier Bottom Layer ....................................................................................... 15
24 Dual-Supply, Multiple Feedback Filter Schematic ..................................................................... 16
25 Dual-Supply, Multiple Feedback Filter Top Layer...................................................................... 16
26 Dual-Supply, Multiple Feedback Bottom Layer......................................................................... 17
27 Dual-Supply, Sallen-Key Filter Schematic .............................................................................. 17
28 Dual-Supply, Sallen-Key Top Layer ..................................................................................... 18
29 Dual-Supply, Sallen-Key Bottom Layer ................................................................................. 18
30 Inverting Comparator Schematic......................................................................................... 19
31 Inverting Comparator Top Layer ......................................................................................... 19
32 Inverting Comparator Bottom Layer ..................................................................................... 20
33 Non-Inverting Comparator Schematic................................................................................... 20
34 Non-inverting Comparator Top Layer.................................................................................... 21
35 Non-Inverting Comparator Bottom Layer................................................................................ 21
36 Riso with Dual-Feedback Schematic...................................................................................... 21
37 Example of fZERO, Where AOL_Loaded = 20 dB .............................................................................. 22
38 Riso Dual-Feedback Top Layer............................................................................................ 23
39 Riso Dual-Feedback Bottom Layer........................................................................................ 23
40 Dual-Supply, Non-Inverting Amplifier Schematic....................................................................... 23
41 Dual-Supply, Non-Inverting Amplifier Top Layer....................................................................... 24
42 Dual-Supply, Non-Inverting Amplifier Bottom Layer................................................................... 24
43 Dual-Supply, Inverting Amplifier Schematic ............................................................................ 25
44 Dual-Supply, Inverting Amplifier Top Layer............................................................................. 26
45 Dual-Supply, Inverting Amplifier Bottom Layer......................................................................... 26
46 SMA Vertical Connectors ................................................................................................. 27
47 SMA Horizontal Connectors .............................................................................................. 27
48 Wire Connections .......................................................................................................... 27
49 Through-Hole Test Points................................................................................................. 28
50 Input and Output Pins in Terminal Area................................................................................. 28
51 Wire Alternative for Terminal Area....................................................................................... 29
List of Tables
1 DIYAMP-SOT23-EVM Kit Contents ....................................................................................... 3
2 Location of Circuit Legend.................................................................................................. 4
3 MFB Filter Type Component Selection ................................................................................... 8
4 Sallen-Key Filter Component Type Selection............................................................................ 9
5 MFB Filter Type Component Selection.................................................................................. 16
6 Sallen-Key Filter Component Type Selection .......................................................................... 18
7 Bill of Materials ............................................................................................................. 30
Trademarks
FilterPro, TINA-TI are trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.

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DIYAMP-SOT23-EVM
1 Introduction
The DIYAMP-SOT23-EVM is an EVM developed to give users the ability to easily evaluate their design
concepts. This break-apart EVM has several popular op-amp configurations including: amplifiers, filters,
and stability compensation configurations for both single and dual supply. The EVM is designed for 0805
and 0603 package size surface mount components enabling easy prototyping. This board gives the user
the ability to build anything from a simple amplifier to complex signal chains by combining different
configurations.
For more information about power supply voltages and input/output limitations, consult TI Precision Labs –
Op Amps videos.
1.1 DIYAMP-SOT23-EVM Kit Contents
Table 1 details the contents included in the DIYAMP-SOT23-EVM kit.
Table 1. DIYAMP-SOT23-EVM Kit Contents
Item Description Quantity
DIYAMP-SOT23-EVM PCB 1
Header Strip 100 mil (2.54 mm) spacing, 32 position, through hole 2
1.2 EVM Features
This EVM supports the following features:
• Multiple circuit configurations
• Dual- and single-supply configurations
• Breadboard compatible
• Schematic provided in silk screen on the PCB
• Multiple connector options for input and output connections: SMA, test point, and wires.
1.3 List of Circuits on the EVM
• Single-supply multiple feedback (MFB) filter
• Single-supply Sallen-Key filter
• Single-supply non-inverting amplifier
• Single-supply inverting amplifier
• Difference amplifier
• Dual-supply multiple feedback (MFB) filter
• Dual-supply Sallen-Key filter
• Riso with dual feedback
• Non-Inverting Comparator
• Inverting Comparator
• Dual-supply non-inverting amplifier
• Dual-supply inverting amplifier

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2 Hardware Setup
Assembly of the DIYAMP-SOT23-EVM involves identifying and breaking out the desired circuit
configuration from the EVM, soldering components, header pins, and inputs and outputs connections. This
section presents the details of these procedures.
2.1 EVM Circuit Locations
Figure 1 and Table 2 map the location of each circuit configuration on the EVM. Figure 1 labels each
circuit configuration with a letter ranging from A to L. Table 2 matches the circuit configuration to a letter in
Figure 1 and also provides the name of each individual circuit written in silk screen on the EVM.
Figure 1. Location of Circuit Configurations
Table 2. Location of Circuit Legend
Circuit Name Silk Screen Label Letter in
Figure 1
Single-supply multiple feedback filter Single-Supply MFB Filter A
Single-supply Sallen Key filter Single-Supply SK Filter B
Single-supply non-inverting amplifier Single-Supply Non-Inverting Amp C
Single-supply inverting amplifier Single-Supply Inverting Amp D
Difference amplifier Difference Amp E
Dual-supply multiple feedback filter MFB Filter F
Dual-supply Sallen Key filter SK Filter G
Inverting comparator Inverting Comparator H
Non-inverting comparator Non-Inverting Comparator I
Riso with dual feedback Riso Dual Feedback J
Dual-supply non-inverting amplifier Non-Inverting Amp K
Dual-supply inverting amplifier Inverting Amp L

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2.2 EVM Assembly Instructions
This section has step-by-step instructions on how to assemble a circuit configuration from the EVM.
Step 1. Choose the desired circuit configuration. See Section 2.1 for the location of each circuit
configuration.
Step 2. Gently flex the PCB panel at the score lines to separate the desired circuit configuration from
the EVM.
Figure 2. Detach Desired Circuit Configuration
Step 3. Solder device and surface mount passive components to the separated PCB.
Figure 3. Detach Configuration With Attached IC and Passive Components
Step 4. Use long-nose pliers to break header strips, provided in the EVM kit, into 4-position lengths.
Figure 4. Terminal Strip (TS-132-G-AA) Broken Into 4-Pin Lengths

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Step 5. Insert header strips into a spare DIP socket as shown in Figure 5.
Figure 5. 4-Pin Length Terminal Strips Inserted in DIP Socket
Step 6. Position separated PCB over pins and solder the connections. Carefully remove from the DIP
socket.
Figure 6. Detached Board Configuration Position Over Terminal Pins
Step 7. Attach SMA connectors, test points, or wires to the input and output of the separated PCB.
Figure 7. Fully-Assembled Circuit Configuration From DIYAMP-SOT23-EVM

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3 Schematic and PCB Layout
This section provides the schematic and PCB layout of each circuit configuration provided on the EVM.
3.1 Schematic PCB Drawing
Each circuit board has a silk screen of its schematic for easy reference.
Figure 8. Silk Screen Circuit Schematic
3.2 Single-Supply, Multiple Feedback Filter
Figure 9 shows the schematic for the single-supply, multiple feedback (MFB) filter circuit configuration.
Figure 9. Single-Supply, Multiple Feedback Filter Schematic
The MFB topology (sometimes called infinite gain or Rauch) is often preferred, due to low sensitivity to
component variations. The MFB topology creates an inverting second-order stage. This inversion may, or
may not, be a concern in the filter application.

c _ Vref
1 2 2
1
2 R / /R C
=p ´ ´ f
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The single-supply, MFB filter circuit can be configured as a low-pass filter, high-pass filter, or band-pass
filter based on the component selection of Z1 through Z5. Table 3 displays the type of passive component
that should be chosen for Z1 through Z5 for each filter configuration.
Table 3. MFB Filter Type Component Selection
Pass-Band
Filter Type Type of Component (Z1) Type of Component (Z2) Type of Component (Z3) Type of Component (Z4) Type of Component (Z5)
Low Pass R1 C2 R3 R4 C5
High Pass C1 R2 C3 C4 R5
Band Pass R1 R2 C3 C4 R5
For additional guidance in designing a filter, download FilterPro™ active filter design software.
Capacitor C2 provides the option to filter noise that may be introduced from the Vref input. calculates the
cutoff frequency due to C2.
(1)
The PCB layout of the top layer of the single-supply, MFB filter configuration is displayed in Figure 10.
Figure 10. Single-Supply, MFB Filter Top Layer
The PCB layout of the bottom layer of the single-supply, MFB filter configuration is displayed in Figure 11.
Figure 11. Single-Supply, MFB Filter Bottom Layer

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3.3 Single-Supply, Sallen-Key Filter
Figure 12 shows the schematic for the single-supply, Sallen-Key filter circuit configuration.
Figure 12. Single-Supply, Sallen-Key Filter Schematic
Sallen-Key is one of the most commonly applied active filter topologies. The Sallen-Key is a non-inverting,
voltage-controlled, voltage-source (VCVS) able to attain larger Qs with a stable response than other filter
topologies. Because Sallen-Key is non-inverting, it might be preferable over the MFB topology.
The single-supply, Sallen-Key filter can be configured as a low-pass filter, high-pass filter, or band-pass
filter based on the component selection of Z1 through Z5. Table 4 displays the type of passive component
that should be chosen for Z1 through Z5 for each filter configuration.
Table 4. Sallen-Key Filter Component Type Selection
Pass-Band
Filter Type Type of Component (Z1) Type of Component (Z2) Type of Component (Z3) Type of Component (Z4) Type of Component (Z5)
Low Pass R1 R2 C3 C4 Not populated
High Pass C1 C2 R3 R4 Not populated
Band Pass R1 C2 R3 R4 C5
For additional guidance in designing a filter, download the FilterPro active filter design software.
The PCB layout of the top layer of the single-supply, Sallen-Key filter circuit configuration is displayed in
Figure 13.
Figure 13. Single-Supply, Sallen-Key Filter Top Layer

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The PCB layout of the bottom layer of the single-supply, Sallen-Key filter configuration is displayed in
Figure 14.
Figure 14. Single-Supply, Sallen-Key Filter Bottom Layer
3.4 Single-Supply, Non-Inverting Amplifier
Figure 15 shows the schematic for the single-supply, non-inverting amplifier circuit configuration.
Figure 15. Single-Supply, Non-Inverting Amplifier Schematic
The non-inverting op-amp configuration takes an input signal that is applied directly to the high
impedance, non-inverting input terminal and outputs a signal that is the same polarity as the input signal.
The load resistance for this topology is the sum of R1 and R2. The values of the resistors in the feedback
network will determine the amount of gain to amplify the input signal.
There are multiple ways to configure the single-supply, non-inverting amplifier. The following cases show
three primary use case configurations for this circuit.

14 ref
2
3
offset
R
1 C V
R
RV
æ ö
+ ´
ç ÷
è ø
=
pole
3 2
1
F2 C R =p´ ´
( )
ZERO
3 1 2
1
F
2 C R R
=p´ +
4
IN ref
3 4
R
V V
R R
+
æ ö
=ç ÷
+
è ø
c
1 2
1
2 R C
=p´ ´ f
1
out in
2
R
V 1 V
R
æ ö
= +
ç ÷
è ø
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Case 1: Standard non-inverting circuit
This circuit board can be configured into a standard non-inverting circuit by shorting C3 and C4 with a 0-Ω
resistor and leaving R3 and R4 unpopulated.
Equation 2 displays the transfer function for the standard single-supply, non-inverting amplifier circuit
configuration.
where
• C3 is shorted with a 0-Ωresistor
• C4 is shorted with a 0-Ωresistor
• R3 is unpopulated
• R4 is unpopulated (2)
Capacitor C2 provides the option to filter the output. The cutoff frequency of the filter can be calculated
using Equation 3.
(3)
Case 2: AC coupled, single-supply, non-inverting circuit
This circuit board can be configured into an AC coupled non-inverting circuit by populating C3 and C4 with
capacitors and populating R3 or R4 with resistors. R3 and R4 are used to set the DC output in the
following two ways:
Option 1: VREF is directly applied to the input IN+
• R3 is populated with the desired biasing resistor
• R4 is unpopulated
Option 2: VREF is divided down and applied to the input IN+
• R3 and R4 are populated with resistors, see Equation 4
(4)
The AC response of the input signal is high-passed through C4, R3 + R4. The op-amp noise-gain is unity-
gain until the gain begins to rise at the zero frequency defined in Equation 5.
(5)
The gain flattens off to the same gain defined in Equation 2 at the frequency defined in Equation 6.
(6)
For more information on the AC coupled non-inverting circuit, see e2e.ti.com.
Case 3: Non-inverting signal scaling circuit
This circuit board can be configured into a non-inverting signal scaling circuit by shorting C3 with a 0-Ω
resistor and populating C4 with a resistor. This forms a 3-resistor divider with R3 and R4 on the input to
scale or shift the input signal level. The op amp is typically configured as a unity-gain buffer.
Step 1. Choose a value for the resistor installed in place of C4
Step 2. Compute R3
(7)

offset 4 3
2
offset 3 offset 4 ref 4
V C R
RV R V C V C
- ´ ´
=´ + ´ - ´
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Step 3. Compute R2
(8)
For more information on the AC coupled non-inverting circuit, see e2e.ti.com.
The PCB layout of the top layer of the single-supply, non-inverting circuit configuration is displayed in
Figure 16.
Figure 16. Single-Supply, Non-Inverting Amplifier Top Layer
The PCB layout of the bottom layer of the single-supply, non-inverting circuit configuration is displayed in
Figure 17.
Figure 17. Single-Supply, Non-Inverting Amplifier Bottom Layer
3.5 Single-Supply, Inverting Amplifier
Figure 18 shows the schematic for the single-supply, inverting amplifier circuit configuration.
Figure 18. Single-Supply, Inverting Amplifier Schematic

c _ Vout
1 4
1
2 R C
=p ´ ´ f
c _ Vref
3 4 2
1
2 R / /R C
=p ´ ´ f
1 4
out in ref
2 3 4
R R
V V V
R R R
æ ö
æ ö
= - + ç ÷
ç ÷ +
è ø è ø
c _ highpass
3 2
1
2 C R
=p´ ´ f
4
out ref
3 4
R
V V
R R
æ ö
=ç ÷
+
è ø
1 1 4
out in ref
2 2 3 4
R R R
V V 1 V
R R R R
æ ö
æ ö æ ö
= - + + ç ÷
ç ÷ ç ÷ +
è ø è øè ø
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The inverting op-amp configuration takes an input signal that is applied directly to the inverting input
terminal and outputs a signal that is the opposite polarity as the input signal. The benefit of this topology is
that it avoids common mode limitations. The load resistance for this topology is equal to R2. The values of
the resistors in the feedback network will determine the amount of gain to amplify the input signal.
The single-supply, inverting amplifier circuit provides the option to AC couple the input, filter the output,
and bias the output of the amplifier to a desired value.
Equation 9 displays the dc transfer function of the single-supply, inverting amplifier circuit configuration.
where
• C3 is shorted with a 0-Ωresistor (9)
Capacitor C3 provides the option to AC couple the input of the single-supply, inverting amplifier by
creating a high-pass filter. Equation 10 displays the dc transfer function of the single-supply, inverting
amplifier circuit configuration.
where
• The input is AC coupled with C3 (10)
The cutoff frequency of the high-pass filter can be calculated using Equation 11.
(11)
Equation 12 displays the transfer function when the frequency of the input signal is above the cutoff
frequency calculated in Equation 11.
(12)
Capacitor C2 filters noise that may be introduced from the Vref input. Equation 13 calculates the cutoff
frequency due to C2.
(13)
Capacitor C4 provides the option to filter the output. The cutoff frequency of the filter can be calculated
using Equation 14.
(14)
The PCB layout of the top layer of the single-supply, inverting amplifier circuit configuration is displayed in
Figure 19.
Figure 19. Single-Supply, Inverting Amplifier Top Layer

( )
1
out IN IN ref
2
R
V V V V
R+ -
= - +
3
4 1 1 1
out IN ref IN
3 4 2 3 4 2 2
R
R R R R
V 1 V 1 V V
R R R R R R R
+ -
æ ö æ ö
æ ö æ ö
= + + + +
ç ÷ ç ÷
ç ÷ ç ÷
+ +
è ø è ø
è ø è ø
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The PCB layout of the bottom layer of the single-supply, inverting amplifier circuit configuration is
displayed in Figure 20.
Figure 20. Single-Supply, Inverting Amplifier Bottom Layer
3.6 Difference Amplifier
Figure 21 shows the schematic for the difference amplifier circuit configuration.
Figure 21. Difference Amplifier Schematic
The difference amplifier utilizes both inverting and non-inverting inputs and produces an output that is
equal to the difference between the inputs. The gain of the difference amplifier is dependent on the ratio of
the resistor values selected.
Equation 15 displays the transfer function of the difference amplifier circuit configuration.
(15)
If R1= R4and R2= R3,Equation 15 can be simplified to Equation 16.
(16)

c
1 1
1
2 R C
=p´ ´ f
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Capacitors C1 and C4 provide the option to filter the output of the amplifier. The cutoff frequency of the
filter can be calculated using Equation 17.
where
• R1= R4, R2= R3, and C1= C4(17)
The PCB layout of the top layer of the difference amplifier circuit configuration is displayed in Figure 22.
Figure 22. Difference Amplifier Top Layer
The PCB layout of the bottom layer of the difference amplifier circuit configuration is displayed in
Figure 23.
Figure 23. Difference Amplifier Bottom Layer

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3.7 Dual-Supply, Multiple Feedback Filter
Figure 24 shows the schematic for the dual-supply, multiple feedback filter circuit configuration.
Figure 24. Dual-Supply, Multiple Feedback Filter Schematic
The MFB topology (sometimes called infinite gain or Rauch) is often preferred due to low sensitivity to
component variations. The MFB topology creates an inverting second-order stage. This inversion may, or
may not, be a concern in the filter application.
The dual-supply, MFB filter circuit can be configured as a low-pass filter, high-pass filter, or band-pass
filter based on the component selection of Z1 through Z5. Table 5 displays the type of passive component
that should be chosen for Z1 through Z5 for each filter configuration.
Table 5. MFB Filter Type Component Selection
Pass-Band
Filter Type Type of Component (Z1) Type of Component (Z2) Type of Component (Z3) Type of Component (Z4) Type of Component (Z5)
Low Pass R1 C2 R3 R4 C5
High Pass C1 R2 C3 C4 R5
Band Pass R1 R2 C3 C4 R5
For additional guidance in designing a filter, download the FilterPro active filter design software.
The PCB layout of the top layer of the dual-supply, multiple feedback filter circuit configuration is displayed
in Figure 25.
Figure 25. Dual-Supply, Multiple Feedback Filter Top Layer

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The PCB layout of the bottom layer of the dual-supply, multiple feedback filter circuit configuration is
displayed in Figure 26.
Figure 26. Dual-Supply, Multiple Feedback Bottom Layer
3.8 Dual-Supply, Sallen-Key Filter
Figure 27 shows the schematic for the dual-supply, Sallen-Key Filter circuit configuration.
Figure 27. Dual-Supply, Sallen-Key Filter Schematic
Sallen-Key is one of the most commonly applied active filter topologies. The Sallen-Key is a non-inverting,
voltage-controlled, voltage-source (VCVS) able to attain larger Qs with a stable response than other filter
topologies. Because Sallen-Key is non-inverting, it might be preferable over the MFB topology.
For this EVM, the Sallen-key filter can be configured for unity-gain by populating R1 with a short and
leaving R2 open. Gain can be added by adding the appropriate resistors to R2 and R1 as explained in
FilterPro.

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The dual-supply, Sallen-Key filter can be configured as a low-pass filter, high-pass filter, or band-pass
filter based on the component selection of Z1 through Z5. Table 6 displays the type of passive component
that should be chosen for Z1 through Z5 for each filter configuration.
Table 6. Sallen-Key Filter Component Type Selection
Pass-Band
Filter Type Type of Component (Z1) Type of Component (Z2) Type of Component (Z3) Type of Component (Z4) Type of Component (Z5)
Low Pass R1 R2 C3 C4 Not populated
High Pass C1 C2 R3 R4 Not populated
Band Pass R1 C2 R3 R4 C5
For additional guidance in designing a filter, download the FilterPro active filter design software.
The PCB layout of the top layer of the dual-supply, Sallen-Key filter circuit configuration is displayed in
Figure 28.
Figure 28. Dual-Supply, Sallen-Key Top Layer
The PCB layout of the bottom layer of the dual-supply, Sallen-Key filter circuit configuration is displayed in
Figure 29.
Figure 29. Dual-Supply, Sallen-Key Bottom Layer

L
2 1
H
V
R R
V V
+
æ ö
=ç ÷
-
è ø
L
3 1
H L
V
R R
V V
æ ö
=ç ÷
-
è ø
2
th ref
1 2
R
V V
R R
æ ö
=ç ÷
+
è ø
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3.9 Inverting Comparator
Figure 30 shows the schematic for the inverting comparator circuit configuration.
Figure 30. Inverting Comparator Schematic
It is important to note that this circuit layout is meant for SOT23 package op amps or push-pull output type
comparators. This configuration uses a voltage divider R1 and R2 to set up the threshold voltage when no
hysteresis is added. The comparator will compare the input signal (Vin) to the threshold voltage (Vth).
where
• R3 is unpopulated (18)
The comparator input signal is applied to the inverting input, so the output will have an inverted polarity.
When Vin > Vth, the output will drive to the negative supply (GND or logic low). When Vin < Vth, the
output will drive to the positive supply (V+ or logic high).
R3 can be populated to implement hysteresis which uses two different threshold voltages to avoid the
multiple transitions. The input signal must exceed the upper threshold (VH) to transition low or below the
lower threshold (VL) to transition high. Equation 19 and Equation 20 will calculate the value of R2 and R3
for the two desired thresholds.
(19)
(20)
The PCB layout of the top layer of the inverting comparator circuit configuration is displayed in Figure 31.
Figure 31. Inverting Comparator Top Layer

( )
( )
th
2 1
l th
V V
R R
V V
+
+
=-
( )
h th
1 2
th
V V
R R
V
-
=
4
th ref
3 4
R
V V
R R
æ ö
=ç ÷
+
è ø
+
±
R1 R2
R4
VOUT
VIN
V+ C1
VREF R3
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The PCB layout of the bottom layer of the inverting comparator circuit configuration is displayed in
Figure 32.
Figure 32. Inverting Comparator Bottom Layer
3.10 Non-Inverting Comparator
Figure 33 shows the schematic for the non-inverting comparator circuit configuration.
Figure 33. Non-Inverting Comparator Schematic
It is important to note that this circuit layout is meant for SOT23 package op amp or push-pull output type
comparators. This configuration uses a voltage divider R3 and R4 to set up the threshold voltage. The
comparator will compare the input signal (Vin) to the threshold voltage (Vth).
(21)
The comparator input signal is applied to the non-inverting input, so the output will have a non-inverted
polarity. When Vin > Vth, the output will drive to the positive supply (V+ or logic high). When Vin < Vth, the
output will drive to the negative supply (GND or logic low).
R2 can be populated to implement hysteresis which uses two different threshold voltages to avoid the
multiple transitions. The input signal must exceed the upper threshold (VH) to transition high or below the
lower threshold (VL) to transition low. Equation 22 and Equation 23 will calculate the value of R1 and R2
for the two desired thresholds.
(22)
(23)