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# Transistor vs diode.

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#### raul260291

##### Junior Member level 1
Hello Everyone,
I am getting confused with transistor and diode stuff. in the active region the characteristics of a transistor i.e acting as voltage controlled current source it resembles a diode.
Even the equations are same including the small signal model equations.
Ic=Is*exp(Vd/Vt) and gm(transconductance)=Ic/Vt.
What is the benefit of using transistor over diode.

Ic=Is*exp(Vd/Vt) and gm(transconductance)=Ic/Vt.
What is the benefit of using transistor over diode.

Hi Raul,
at first - the transistor is a three-terminal device in contrast to the diode with only two terminals.
This alone does not answer your question - however, the main difference is that in the above formula the voltage Vd
* is the voltage across the diode (that means: the voltage across the two terminals that see the current)
* is the voltage across the B-E junction of the transistor, which means: NOT across the two terminals through which the current Ic goes.
Thus you can control the current Ic with the voltage Vd - and Ic can be much larger than the current which is driven by Vd directly through the B-E path.

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raul260291

### raul260291

Points: 2
Can we design an amplifier using Diodes?

Can we design an amplifier using Diodes?

A diode can be seen as a resistor that is strongly non-linear. That`s all.
Can you find an answer by yourself?

raul260291

What is the benefit of using transistor over diode.

Voltage, current, and power amplification.

Ratch

Can we design an amplifier using Diodes?
Only if it is a diode with a negative resistance region such as a tunnel diode.

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