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[Amps] a 'circuits' question

To: amps <amps@contesting.com>
Subject: [Amps] a 'circuits' question
From: Dan Sawyer <dansawyer@earthlink.net>
Date: Wed, 08 Sep 2004 06:44:21 -0700
List-post: <mailto:amps@contesting.com>
This is a circuits question from a 575 curve tracer being used to match MOSFETs for an HF amp so it is a least close to topic. The problem is the difference in granularity between the 'steps' circuit and the 'zero' adjust circuit. The bias of the power MOSFETs is high enough so that only higher numbered steps get displayed the granularity per step is too high. The result is only 2 steps per trace get displayed.

The circuit that produces this is a voltage adder with the steps input coming through a 90K Ohm resister and the bias coming through a 600K ohm. My question is can I substitute a smaller resister for the bias? I was thinking of 150K ohm. This would effectively increase the bias to the point where it was turning on the MOSFET and the steps drive could be reduced to a low enough value where multiple steps were observed.

Is this a feasible modification??

Thanks,
Dan

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