hi
i study a FET common source amplifier and i make a simulation first in circuit make pro 200 and multisim
i use a ac signal with peak amplitude 20mV and frequency 1 KHz the outiput signal have difference amplitude in two simulation
program
in multisim the amplitude of output signal is 244,mV
and is circut maker pro 2000 is 770.75 mV
what is this difference due to?

thank George

 

Are your sure the two input signals are identical?

Otherwise it may be a difference in the two transistor models.
You circuit depends upon the transconductance (gm) or admittance (Yfs) gain of the transistor, and the two models may have a different value for that.

Normally, you want to design a circuit with negative feedback, so the gain is not highly dependent on the transistor gain, since that has significant unit-to-unit variations in real devices (look at the data sheet which shows over a 2:1 variation).

 

You have two different transistors, so should expect some gain difference.

 

You have two different transistors, so should expect some gain difference.

Right.
I didn't see the difference between the 5 and 6 until I enlarged the picutre.

 

yes meaybe the diference type of fet in multisin the BF245C DONT WORK !

 

with the same type of fet BF256c the two simulation program have different output

 

yes meaybe the diference type of fet in multisin the BF245C DONT WORK !

In practice, feedback is used to ensure that parameters like Gain is independent of the Active Device ( transistor, FET, ....) Parameter variations.
If you remove that 25uF capacitor, you will implement an AC feedback, and your gain should be almost the same, about 4.

 

with the same type of fet BF256c the two simulation program have different output

Then that's almost certainly down to differences in the models used.

 

In practice, feedback is used to ensure that parameters like Gain is independent of the Active Device ( transistor, FET, ....) Parameter variations.
If you remove that 25uF capacitor, you will implement an AC feedback, and your gain should be almost the same, about 4.

yes! when remove the capacitor then the gain from the two different sofware are equal