1
4
ref
2
3
offset
R
1
C
V
R
R
V
æ
ö
+
´
ç
÷
è
ø
=
pole
3
2
1
F
2
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
www.ti.com
Schematic and PCB Layout
11
SBOU191 – July 2017
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Copyright © 2017, Texas Instruments Incorporated
DIYAMP-SOT23-EVM
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-
Ω
resistor
•
C4 is shorted with a 0-
Ω
resistor
•
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)