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neo
Joined: 19 Aug 2004
Posts: 56
Location: Beijing
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 20 Aug 2004 14:27 how to get Gm. |
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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!
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Mazz
Joined: 03 Nov 2001
Posts: 473
Helped: 56
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| 20 Aug 2004 15:52 Re: how to get Gm. |
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Any AC simulator can calculate the Gm: just follow the definition and plot the output signal current vs. the input signal voltage.
Mazz
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hspice
Joined: 10 Jul 2004
Posts: 7
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| 21 Aug 2004 9:54 Re: how to get Gm. |
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| For a transistor, just do DC analyze and use calculator-> OP -> selecting component -> gm, print it
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Hughes
Joined: 10 Jun 2003
Posts: 711
Helped: 84
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| 25 Aug 2004 8:43 Re: how to get Gm. |
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| 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.
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Question
Joined: 11 Aug 2004
Posts: 76
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| 25 Aug 2004 10:53 how to get Gm. |
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| For a transistor you can get gm from Results-Print-DC Operating Points after DC simulation.
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DoctorX
Joined: 02 Sep 2004
Posts: 73
Location: USA
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| 15 Sep 2004 2:13 Re: how to get Gm. |
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| 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.
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markl
Joined: 16 Sep 2004
Posts: 4
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| 16 Sep 2004 23:15 Re: how to get Gm. |
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| Hughes wrote: |
| 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.
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Hughes
Joined: 10 Jun 2003
Posts: 711
Helped: 84
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| 17 Sep 2004 15:44 Re: how to get Gm. |
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| markl wrote: |
| Hughes wrote: |
| 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.
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sutapanaki
Joined: 02 Nov 2001
Posts: 476
Helped: 16
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| 17 Sep 2004 17:38 Re: how to get Gm. |
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How to plot transistor's gm and other intrinsic parameters, see:
http://www.edaboard.com/viewtopic.php?t=70540&highlight=
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