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How can i choose differential amplifier

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Esakki raja

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Hi

In differential amplifier we are using the current source how can i decide the current value for the amplifiers design.
 

* You do not want to waste current. I believe you want just enough current flowing, so that your differential amplifier operates in a region where you get linear response from it.

* Your source signals can supply a certain amount of current. You need to make these levels compatible with your differential amplifier, so that current levels affect each other correctly.
 
Thanks Brad

For example I need 40 dB gain for my amplifier design means Is there any relation to the current vs gain.

Because if it has any relation then I choose the current from that relation to achieve my gain spec.
 

Esakki raja said:
Thanks Brad

For example I need 40 dB gain for my amplifier design means Is there any relation to the current vs gain.

Because if it has any relation then I choose the current from that relation to achieve my gain spec.
Click to expand...

The transistor is a voltage controlled device and the gain depends on the transconductance gm=d(Ic)/d(Vbe).
Because the function Ic=f(Vbe) has an exponential form it is easy to find the slope gm=Ic/Vt (Ic=Dc current and Vt=thermal voltage).
The transconductance gm appears in the formula for the voltage gain.
 
Thanks LvW

Now i got it .Its very helpful to me

Thanks a lot........
 

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