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ethan
Joined: 07 Jul 2004
Posts: 66
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 12 Jul 2004 21:15 Ask for cut-off frequency simulation procedure in Cadence |
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| Has anyone done this so far? I asked this question several days ago. But no reply
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alvays
Joined: 07 Jul 2004
Posts: 64
Helped: 3
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| 22 Jul 2004 15:22 Re: Ask for cut-off frequency simulation procedure in Cadenc |
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do you mean the gain band width?or fT?
Is it the frequency when gain=1?
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totoro
Joined: 27 Jun 2004
Posts: 86
Helped: 10
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| 22 Jul 2004 16:23 Re: Ask for cut-off frequency simulation procedure in Cadenc |
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| just the unit gain frequecy
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ethan
Joined: 07 Jul 2004
Posts: 66
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| 28 Jul 2004 16:41 Re: Ask for cut-off frequency simulation procedure in Cadenc |
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| totoro wrote: |
| just the unit gain frequecy |
right. Just look at my another post for cut-off frequency simulation. There was reply there.
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yjkwon57
Joined: 31 Jul 2004
Posts: 221
Helped: 21
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| 02 Aug 2004 0:10 Re: Ask for cut-off frequency simulation procedure in Cadenc |
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Hi.
Since the transistor parameters are usually obtained in a typical operation region, you may not obtain the fT frequency directly from the simulation. Instead, you will obtain the gain at -3dB cutoff frequency, and fT will be obtained by extrapolating the curve. Since the frequency characteristics of the transistor shows only one pole, the result obtained from the extrapolation will be fairly correct. If you want to get the correct fT, then, you will use the network analyzer. The frequency at which the parameter s_21 is unity is the fT.
Bye~~~
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yjkwon57
Joined: 31 Jul 2004
Posts: 221
Helped: 21
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| 02 Aug 2004 22:51 Re: Ask for cut-off frequency simulation procedure in Cadenc |
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Hi.
I did one mistake in the former reply. When you use a network analyzer, I said like this:
The frequency at which the parameter s_21 is unity is the fT. <= wrong
The AC beta is represented by the scattering parameters as follows:
beta=-s21/{(1-s11)(1+s22)+s12s21} <= correct
You may use a computer for this conversion, just as I did.
Bye~~
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