Electronic – Opamp AB Class Current Buffer

buffercurrentoperational-amplifier

I am trying to design 100W (100V – 1A) Opamp Current Buffer with unity voltage gain. I will use PA441 or LT6090 opamp.

Apex published a circuit for this amplifier. Please look at page 3 from the link below

https://apexanalog-public.sharepoint.com/Resources/AN52U.pdf

Shared circuit is for inverting amplifier configuration. I need non-inverting configuration. When I tried the circuit in LTSpice, for negative side, it seems works well. But for positive side there is a problem witn nmos i could not handle.

Circuit Schematic

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How could I amplify 0 to 100V 100mA output to 0 to 100V 1A with non-inverting configuration?

I would be very glad if anybody could help. Thanks.

Best Answer

At a guess, your PA341 is bad. Try disconnecting the buffer, and just close the loop with about a 10k load resistor.

EDIT - Since the PA341 is good, a closer look establishes your problem. The app note clearly requires a depletion-node FET, and you are using an enhancement-mode part. They do not work the same.

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