GATE Electrical – Analog Electronics
Page 19 : Differential Amplifier
A Differential Amplifier is a circuit that amplifies the difference between two input signals while rejecting signals common to both inputs.
It is the basic building block of Operational Amplifiers (Op-Amps).
Basic Concept
A differential amplifier has two inputs:
- Input 1 : V1
- Input 2 : V2
The output voltage depends on the difference between these two inputs.
Vout = Ad (V1 − V2)
Where:
- Ad = Differential Gain
Types of Input Signals
1. Differential Mode Input
Two input signals are equal in magnitude but opposite in phase.
Vd = V1 − V2
The amplifier produces maximum output for differential signals.
2. Common Mode Input
Both inputs receive the same signal.
Vc = (V1 + V2) / 2
Ideally the amplifier should reject common mode signals.
Common Mode Rejection Ratio (CMRR)
CMRR measures the ability of the amplifier to reject common mode signals.
CMRR = Ad / Ac
Where:
- Ad = Differential gain
- Ac = Common mode gain
In decibels:
CMRR(dB) = 20 log10 (Ad / Ac)
Applications
- Operational amplifiers
- Instrumentation amplifiers
- Noise rejection circuits
- Signal processing systems
Important GATE Points
- Differential amplifier amplifies difference between inputs.
- Rejects common signals.
- High CMRR is desirable.
- Foundation of operational amplifiers.
Next Page → Differential Amplifier Analysis (Gain Derivation)
.png)
No comments:
Post a Comment