### Which transistor has higher gain. BJT or MOS and why?

Posted:

**Sat Apr 19, 2014 10:36 am**Which transistor has higher gain. BJT or MOS and why?

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Posted: **Sat Apr 19, 2014 10:36 am**

Which transistor has higher gain. BJT or MOS and why?

Posted: **Wed Apr 30, 2014 10:10 pm**

BJT have more gain than MOSFET because MOSFET shows Quadratic I-V characteristics and BJT shows Exponential I-V characteristics and the change in exponential behavior is more as compared to Quadratic behavior.

In mathematical terms:

The**Intrinsic Gain in BJT = Va/Vt**

where Va is Early Voltage.

It is a process parameter and its value lies in between 35V to 130V. Vt is thermal voltage and its value is 0.025V at room temperature. So, its Intrinsic Gain ranges from 1000 V/V to 5000 V/V.

In**MOSFET Intrinsic Gain is 2Va/(Vgs - Vth) **

where Va is Early Voltage same as in BJT.

Vgs is Gate to Source Voltage

Vth is threshold voltage

(Vgs - Vth) is higher as compared to thermal voltage Vt.

Normally (Vgs - Vth) is considered in between (0.2 -0.4).

So, MOSFETs have lower intrinsic gain as compared to BJT.

In mathematical terms:

The

where Va is Early Voltage.

It is a process parameter and its value lies in between 35V to 130V. Vt is thermal voltage and its value is 0.025V at room temperature. So, its Intrinsic Gain ranges from 1000 V/V to 5000 V/V.

In

where Va is Early Voltage same as in BJT.

Vgs is Gate to Source Voltage

Vth is threshold voltage

(Vgs - Vth) is higher as compared to thermal voltage Vt.

Normally (Vgs - Vth) is considered in between (0.2 -0.4).

So, MOSFETs have lower intrinsic gain as compared to BJT.

Posted: **Thu Jul 24, 2014 9:09 am**

The transconductance of BJT is higher than that of MOSFET which makes the gain of BJT higher than MOSFET.