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14th May 2019, 02:19 #1
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A zero at folded cascode apmlifier
Why there is a zero by counting the gain from the input to node2. Why the gain at high frequency is gm1/gm2? Thanks.
page 10.
http://ece.tamu.edu/~spalermo/ecen47...ascode_ota.pdf

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15th May 2019, 18:13 #2
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Re: A zero at folded cascode apmlifier
Because looking into the source of at low enough frequencies you see big resistance and gain is defined by ro1ro5. When CL reduces the impedance at the output, then looking into n2 you start seeing 1/gm2 and you get the behavior shown on the plots.
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15th May 2019, 20:53 #3
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16th May 2019, 05:09 #4
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Re: A zero at folded cascode apmlifier
That's really helpful. Could you please explanate the zero? Why there is a zero and why the zero location is that? Thank you.

16th May 2019, 21:11 #5
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17th May 2019, 15:11 #6
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Re: A zero at folded cascode apmlifier
Wz is a zero location.
I didn't know what the zero location calculation can also use the gainbandwidth constant relationship to obtain. Thanks.

17th May 2019, 18:10 #7
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Re: A zero at folded cascode apmlifier
The gain bandwidth relation just relates two frequencies on a + or  20db/dec response. It doesn't care if you call one frequency a zero or a pole or just pick two frequencies on the slope.
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