# 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.

#### LvW 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.

Last edited:
• raul260291

### raul260291

points: 2

#### raul260291

##### Junior Member level 1 Can we design an amplifier using Diodes?

#### LvW 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?

#### Ratch raul260291

What is the benefit of using transistor over diode.
Voltage, current, and power amplification.

Ratch

#### crutschow 