input resistance vs freq

[bjtjfet]

i tried to attain input resistance vs frequency of a simple single mosfet amplifier , but i couldnt figure out how?????, i need help , please ,This is very urgent

---------- Post added at 18:32 ---------- Previous post was at 18:29 ----------

excuse me , i forgot mention through which simulator, i use hspice

 

[erikl]

In series with your DC gate bias instance a 1A ac current source, probe the input node, and run an ac analysis. The ac voltage (in units of kV or MV) vs. frequency corresponds to the input impedance (in units of kΩ resp. MΩ) vs. frequency.

 

[bjtjfet]

In series with your DC gate bias instance a 1A ac current source, probe the input node, and run an ac analysis. The ac voltage (in units of kV or MV) vs. frequency corresponds to the input impedance (in units of kΩ resp. MΩ) vs. frequency.

thank you dear erikl, how about the output impedence ? is it the same vice versa ????

 

[jimito13]

Yes the procedure is identical,but don't forger to ground the signal source at your input but keep it's bias.

 

[bjtjfet]

Yes the procedure is identical,but don't forger to ground the signal source at your input but keep it's bias.

thanks alot guys i've do it .

 

[erikl]

... how about the output impedence ? is it the same vice versa?

Same method, yes. In order not to short-circuit a possible DC output level, inject the 1A ac current through a sufficiently large capacitor (F, kF, MF), depending on the expected output resistance and LF limit.