Semiconductor Devices - Convenient Operational Amplifiers
The following figure shows an inverting amplifier. The input signal is amplified and inverted. This is the most widely used constant gain amplifier circuit.
V o = -R f .V in / R 1
Voltage gain A = (-R f / R 1 )
The following figure shows an operational amplifier circuit that operates as a non-inverting or constant gain amplifier and multiplier he has a bettere frequency stability.
The input signal is amplified, but it is not inverted.
Output V o = [(R 1 + R f ) / R 1 ] V 1
Voltage gain A = (R 1 + R f ) / R 1
Inverted summing amplifier
The following figure shows an inverting summing amplifier. This is The most widely used circuit in the op-amp. The circuit shows a three input summing amplifier, which provides a way to algebraically sum three voltages, each multiplied by a constant gain factor. The output voltage is expressed ase follows:
V o = [(-R 4 / R 1 ) V 1 ] [(- R 4 / R 2 ) V 2 ] [( - R 4 / R 3 ) V 3 ]
V o = -R 4 (V 1 / R 1 + V 2 / R 2 + V 3 / R 3 )
If, R 1 = R 2 = R 3 = R 4 = R & R s = R / 3
V o = - (V 1 + V 2 + V 3 )