differential amplifiers

Hello Amey,

I'm not sure exactly what you're looking for when you say "how the differential amplifier design has been proposed."

Any standard operational amplifier is a differential ampflier because it amplifies the differential voltage present at the input terminals ( (IN+ - IN-)*Gain ).

Since the open-loop gain of a standard amplifier is very large (10,000V/V - 10,000,000V/V) negative feedback must be applied to limit the gain so the amplifier output isn't driven into the supply rails for even very small differntial voltages.

Standard amplifiers can be configured as difference amplifiers or instrumentation amplifiers by applying external components and/or a combination of a few amplifiers, please see the below wikipedia articles that describe these:

 http://en.wikipedia.org/wiki/Differential_amplifier

http://en.wikipedia.org/wiki/Instrumentation_amplifier

Regards,
Collin Wells
Precision Linear Applications

thanks for the reply sir..

but i wanted to know how the design of  basic differential amplifier came.(plz give full design including calculations  if possible)

differential amplifier can also be done by taking two separate transistors.then what is the need of this emitter shorting.

i read the book many times but unable to understand....please explain...