Operational Amplifiers – Complete Theory
Page 14 – Instrumentation Amplifier
An Instrumentation Amplifier is a precision amplifier designed to amplify small differential signals while rejecting common-mode noise.
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Main Characteristics
- Very high input impedance
- High Common Mode Rejection Ratio (CMRR)
- Accurate gain control
- Low noise amplification
Basic Structure
The instrumentation amplifier uses three operational amplifiers.
- Two op-amps act as input buffers
- One op-amp acts as differential amplifier
Gain Equation
Vout = (1 + 2R / Rg) × (V2 − V1)
Where:- Rg → Gain controlling resistor
- V1, V2 → Input voltages
Why Instrumentation Amplifier?
- Amplifies very small signals
- Rejects common-mode noise
- Provides stable and accurate gain
Applications
- Biomedical instruments (ECG, EEG)
- Sensor signal amplification
- Data acquisition systems
- Industrial measurement systems
GATE Important Points
- Uses three op-amps
- Very high input impedance
- High CMRR
- Gain controlled by resistor Rg
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