How to get the Gm of an OTA ?

[neo]

how to get Gm.

hi, brothers, i am studying an active filter but i donnot know how to get the Gm of the OTA, can Cadence analog artist do this job? how? using the calculator or else?
thanks a lot!

 

[Mazz]

Re: how to get Gm.

Any AC simulator can calculate the Gm: just follow the definition and plot the output signal current vs. the input signal voltage.
Mazz

 

[hspice]

Re: how to get Gm.

For a transistor, just do DC analyze and use calculator-> OP -> selecting component -> gm, print it

 

[Hughes]

Re: how to get Gm.

By adding a expression OP("/M1", "gm") as output, gm vs sweep source curve can be plotted after DC sweep. M1 is the instance name in the top cellview.

 

[Question]

how to get Gm.

For a transistor you can get gm from Results-Print-DC Operating Points after DC simulation.

 

[DoctorX]

Re: how to get Gm.

If you mean the Gm of a multiple-transistor OTA circuit, you have to test it. You want to put a dc/ac source at input, a dummy voltage source at output, and do dc, TRAN AND ac analysis. At small signals, the result from dc and TRAN should agree with that from ac analysis. Otherwise you got a problem.

 

[markl]

Re: how to get Gm.

By adding a expression OP("/M1", "gm") as output, gm vs sweep source curve can be plotted after DC sweep. M1 is the instance name in the top cellview.

This does not work, it only prints the value.

 

[Hughes]

Re: how to get Gm.

By adding a expression OP("/M1", "gm") as output, gm vs sweep source curve can be plotted after DC sweep. M1 is the instance name in the top cellview.

This does not work, it only prints the value.

If the DC sweep is not selected, OP("M1","gm") can only get a scalar value which will be printed in the simulation window. But if DC sweep is selected, OP("M1","gm") will be a wave and can be plotted in the wave window.

 

[sutapanaki]

Re: how to get Gm.

How to plot transistor's gm and other intrinsic parameters, see: