What is a differential amplifier? Also, explain CMRR.

Electrical and Electronic Engineering - Interview Questions

Differential Amplifier : The amplifier, which is used to amplify the voltage difference between two input-lines neither of which is grounded, is called differential amplifier. This reduces the amount of noise injected into the amplifier, because any noise appearing simultaneously on both the input-terminals as the amplifying circuitry rejects it being a common mode signal.

CMRR : It can be defined as the ratio of differential voltage-gain to common made voltage gain. If a differential amplifier is perfect, CMRR would be infinite because in that case common mode voltage gain would be zero.

Recently Updated Interview Questions in Electrical and Electronic Engineering

What are the advantages of VSCF wind electrical system?

Advantages of VSCF wind electrical system are :

* No complex pitch changing mechanism is needed.
* Aero turbine always keeps going at maximum efficiency point.
* Extra energy in the high wind speed region of the speed – duration curve can be extracted
* Significant reduction in aerodynamic stresses, which are associated with constant – speed operation.

Why electricity in India is in the multiples of 11 like 11kv, 22kv, 33kv?

Transformer Induced voltage equation contains 4.44 factor.

E=4.44*f*T*phi
E -Induced emf per phase
T -number of turns
f -frequency
phi -maximum flux per pole
From the equation we see that E is proportional to 4.4 and it is in turn multiple of 11.

So always transmission voltage is multiple of 11