Tuesday, 10 March 2026

Operational Amplifiers – Complete Theory

Page 6 – Voltage Follower (Buffer Amplifier)

The Voltage Follower is a special case of the non-inverting amplifier.

In this circuit the output is directly connected to the inverting terminal.

Picture used in analog electronics

Circuit Configuration

Input applied to non-inverting terminal (+)
Output connected directly to inverting terminal (−)
No external feedback resistor

Virtual Short Concept

For an ideal op-amp:

V+ ≈ V−

Since

V+ = Vin

and output is connected to the inverting terminal:

V− = Vout

Therefore

Vout = Vin

Voltage Gain

Av = Vout / Vin = 1

This is why it is called a Unity Gain Amplifier.

Important Characteristics

Very high input impedance
Very low output impedance
Gain = 1
No phase inversion

Applications

Impedance matching
Signal buffering
Isolation between circuits
Sensor interface circuits

GATE Important Points

Voltage follower = unity gain amplifier
Gain = 1
Used for impedance matching
Output follows input voltage

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