Electronics > Beginners

Measuring transconductance of any circuit

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Wimberleytech:
Here is another way.

Build the test setup using current source and controlled source as shown.
Run transient analysis.
Measure the voltage at the input of the DUT.
Since I and V are known, calculate GM.

promach:

--- Quote ---Build the test setup using current source and controlled source as shown
--- End quote ---

1) Is E1 a transconductance simulation element ? If yes, it seems not really practical to assign value of 100 to E1 ?

2) Any reason for using "sine" current source ?

3) Why transient analysis ? I suppose doing a DC sweep across Vin and doing derivative on Iout and Vin is the definition of Gm ?

Wimberleytech:

--- Quote from: promach on December 16, 2018, 01:16:32 am ---
--- Quote ---Build the test setup using current source and controlled source as shown
--- End quote ---

1) Is E1 a transconductance simulation element ? If yes, it seems not really practical to assign value of 100 to E1 ?

--- End quote ---
Why (Why not)?
E1 is functioning like an opamp.  Something higher than 100 would be better, but I was concerned about convergence.

--- Quote ---2) Any reason for using "sine" current source ?

--- End quote ---
It is easy...it works

--- Quote ---3) Why transient analysis ? I suppose doing a DC sweep across Vin and doing derivative on Iout and Vin is the definition of Gm ?

--- End quote ---
You do not need to do a derivative.  Measure delta voltage...you know the delta current.  Algebra.

promach:
Did you forget the capacitor which is the important component in a gyrator implementation of inductor ?

Wimberleytech:

--- Quote from: promach on December 16, 2018, 01:30:14 am ---Did you forget the capacitor which is the important component in a gyrator implementation of inductor ?

--- End quote ---

No.  I am calculating Gm.  Certainly Gm has some frequency dependence...you can factor that in when you pick the sine frequency. 

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