DIFFERENCE AMPLIFIER OR SUBTRACTOR
Derive the out put voltage equation :
1
, ctd
Difference (or differential) amplifiers are used in various
applications where there is a need to amplify the difference
between two input signals.
This is a device that amplifies the difference between two
inputs but rejects any signals common to the two inputs.
Considering the op amp circuit shown in Figure above:
There is no current that passes through the op amp
terminals(i.e Inverting and Non Inverting).Hence the
current is zero at the two terminals, and
Va = Vb
2
, ctd
Calculating the voltage at the non inverting terminal using
voltage divider rule:
When resistors R1 = R3 and R2 = R4
Vb = [R2 / R1 + R2] V2 ….Using Voltage Divider Rrule
Hence, Va = Vb = [R2 / R1 + R2] V2. ……………(i)
Current (I1) : Flowing from V1
Current (I2) : Through feedback resistor
3
Derive the out put voltage equation :
1
, ctd
Difference (or differential) amplifiers are used in various
applications where there is a need to amplify the difference
between two input signals.
This is a device that amplifies the difference between two
inputs but rejects any signals common to the two inputs.
Considering the op amp circuit shown in Figure above:
There is no current that passes through the op amp
terminals(i.e Inverting and Non Inverting).Hence the
current is zero at the two terminals, and
Va = Vb
2
, ctd
Calculating the voltage at the non inverting terminal using
voltage divider rule:
When resistors R1 = R3 and R2 = R4
Vb = [R2 / R1 + R2] V2 ….Using Voltage Divider Rrule
Hence, Va = Vb = [R2 / R1 + R2] V2. ……………(i)
Current (I1) : Flowing from V1
Current (I2) : Through feedback resistor
3
