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20th January 2019, 11:56 #1
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zero AC gain of CMOS inverter
Why is the following AC analysis of CMOS inverter resulted in zero AC gain (vout/vin) ?

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20th January 2019, 14:23 #2
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Re: zero AC gain of CMOS inverter
The feedback resistor has a value of 1E20 ??? Typing error?

20th January 2019, 14:45 #3
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Re: zero AC gain of CMOS inverter
vout/vin isn't zero, it's about 42 at 1 Hz starting frequency according to the plot. At GHz frequencies, vout is shorted by 1 nF Cout. Unreasonable setup, inappropriate plot parameters. You may want to plot with log frequency scale to better see what's happening.
The feedback resistor has a value of 1E20?

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22nd January 2019, 02:13 #4
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Re: zero AC gain of CMOS inverter
See the alter section which basically trying to switch on and off certain branches of the circuit.
By the way, removing cout solves the zero AC gain issue. Note that the RC time constant = 100G*1n = 100s , or 0.01Hz filtering.

22nd January 2019, 08:32 #5
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Re: zero AC gain of CMOS inverter
Note that the RC time constant = 100G*1n = 100s , or 0.01Hz filtering.
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22nd January 2019, 11:32 #6
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Re: zero AC gain of CMOS inverter
You still didn't plot the gain with reasonable frequency scale?
Or you mean something else ?

22nd January 2019, 11:37 #7
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Re: zero AC gain of CMOS inverter
Yes, as suggested in post #3.
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