differential amplifier

legend killer said:

Hi everyone,
I am studying diffrential amplifier and opamps.
I am having confusion regarding the commom emitter resistor of differential amplifier.Why d0 we need to conmbine the two emitters.What difference will it make if we connect two different resistors with each emitter.

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legend killer said:

that means two different resistors will not make a difference amplifier

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ericgibbs said:

hi,
The answers in the name 'differential'.
Its a difference amplifier, its the difference of the voltage on base1 and base2 that is amplified and the amplified difference appears at collector1 and collector2.

If only base1 is driven by an external voltage the signal is coupled via its emitter1 to the emitter2.
Base2 can be held at a steady voltage, so the emitter1 signal thru to the emitter2 appears as signal of the opposite polarity/sense to the signal on base1.

So on the collectors you have a 'push pull' signal.

The common emitter resistor connects the two emitters together.
OK

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legend killer said:

Actually I didnt understand properly
Can u please explain in some detail
or suggest a good website

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ericgibbs said:

Hi LK,
I little bedtime reading..

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