Question

Most of linear ICs are based on the two transistor differential amplifier because of its
1. Input voltage dependent linear transfer characteristic
2. High voltage gain
3. High input resistance
4. High CMRR

Answer 1

Correct Answer - Option 4 : High CMRR

CMRR: It stands for Common Mode Rejection Ratio and it is defined as the ratio of differential voltage gain to common-mode voltage gain.

CMRR = A_d / A_c

Where A_d is Differential voltage gain

A_c is a common-mode voltage gain. 

• It indicates the ability of an op-amp to reject common-mode noise signals and to amplify desired differential mode signal.
• The ideal op-amp will have the infinite CMRR and with the finite differential gain and zero common-mode gain.
• High CMRR can be achieved by employing two-transistor differential amplifiers in ICs.

 

Advantages of Differential Amplifier:

• Differential Amplifier has noise cancellation property.
• Differential Amplifiers can reduce external interference.
• The nature of these amplifiers is linear.
• These amplifiers help to increase CMRR(Common Mode Rejection Ratio) which further helps to avoid unwanted signals.