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
ǒ
R112
R109
Ǔ
)
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
ǒ
R111
)
R113
R113
Ǔ
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
+
–
Vin
Vout = Vin
R112
R109
R112
R109
Jumper
Jumper
TLV431ACDBV5
Jumper 104+ to VREF1
=
R102
R103
(
)
+ VREF1
0.1
µ
F
10
µ
F
2.2 k
Ω
A1 FLT
R106
C103
8
1/SD
C105
C106
10
µ
F
