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Charge amplifier (Read 1648 times)

arduino New Member Offline Posts: 4	Charge amplifier Sep 22^nd, 2009, 3:15am hello...i have a problem with my charge amplifier....in particular with the N-MOS. when i increment the dc current the Vout go to 3.8V while Vin decrement. someone can help me to understood it??? thanks
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mimic

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Re: Charge amplifier
Reply #1 - Sep 22^nd, 2009, 11:36pm

Hi,
Does this circuit settle to a stable operating point when there is no input signal applied? Generally your first steps should be to design your DC points for this scenario.

I see a common source stage + a soure follower.. what I cannot understand is how the feedback (capacitor + nmos) guarantees the closed loop gain. Is that path ok?

Certainly the fact that you see 3.8V at output while your Vdd is 3.3 point to an issue linked to bad DC points.

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ywguo Community Fellow Offline Posts: 943 Shanghai, PRC	Re: Charge amplifier Reply #2 - Sep 23^rd, 2009, 3:00am Hi arduino, Have you checked the voltage at drain of M8, which is also the gate of M9? I guess it is not a proper value because the common source amplifier composed of M8 and an ideal current source. Try to replace it with a resistor or a NMOS loading. Best Regards, Yawei
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