Operational Amplifiers – Complete Theory
Page 5 – Non-Inverting Amplifier (Derivation)
The Non-Inverting Amplifier is another important op-amp configuration.
In this circuit the input signal is applied to the non-inverting terminal (+) of the op-amp.
Circuit Components
- Feedback resistor → Rf
- Ground resistor → R1
- Operational amplifier
Virtual Short Concept
For an ideal op-amp:
V+ ≈ V−
Since input is applied to the non-inverting terminal:
V+ = Vin
ThereforeV− ≈ Vin
Voltage at Inverting Terminal
The inverting terminal is connected to a voltage divider.
V− = Vout × ( R1 / (R1 + Rf) )
Since V− = VinVin = Vout × ( R1 / (R1 + Rf) )
Output Voltage
Rearranging the equation:
Vout = Vin ( 1 + Rf / R1 )
Voltage Gain
Av = Vout / Vin = 1 + (Rf / R1)
Important Properties
- No phase inversion
- High input impedance
- Stable amplifier configuration
- Gain controlled by feedback resistors
GATE Important Points
- Gain = 1 + (Rf / R1)
- Input applied to non-inverting terminal
- Output in phase with input
- High input resistance
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