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Differential Amplifier
3-4
Example Circuits
3.4 Differential Amplifier
Figure 3–3 shows area 100 equipped with a single operational amplifier
configured as a differential amplifier using a voltage reference and single
power supply.
Basic setup is done by choice of input and feedback resistors. The transfer
function for the circuit as shown is:
V
OUT
V
IN
R112
R109
VREF1
Where:
R112
R109
R102
R103
The TLV431 adjustable precision shunt regulator, configured as shown,
provides a low impedance reference for the circuit at about 1/2 V1+ in a 3-V
system. Another option is to adjust resistors R111 and R113 for the desired
VREF1 voltage. The formula for calculating VREF1 is:
VREF1 1.24 V
R111 R113
R113
Figure 3–3. Single Operational Amplifier Differential Amplifier With Single Supply Using
Area 100
C107 C108
C104
V1+
V1–
V1+
GND1
V1–
Power Supply Bypass
+
–
7
6
4
3
2
V1+
V1–
R112
C109
R114
C110
R110
R109
R104
R103
R102
R105
C101
C102
1OUT
101–
102–
103+
104+
R111
C
R
A
U102
R113
Voltage Reference
U101
V1+
VREF1 = 1.24 V
R108
+
–
V
in
V
out
= V
in
R112
R109
R112
R109
Jumper
Jumper
TLV431ACDBV5
Jumper 104+ to VREF1
=
R102
R103
()
+ V
REF1
0.1 µF 10 µF
2.2 kΩ
A1 FLT
R106
C103
8
1/SD
C105
C106
10 µF