Posted on Sep 8, 2012

Often a circuit will be called upon to perform several functions. In these situations, the variable gain configuration of this circuit could be quite useful. This programmable gain stage depends on CMOS analog switches to alter the amount of feedback, and thereby, the gain of the stage. Placement of the switching elements inside the relatively lowcurrent area of the feedback loop, minimizes the effects of bias currents and switch resistance on the calculated gain of the stage.

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Voltage spikes can occur during the switching process, resulting in temporarily reduced gain because of the makebefore- break operation of the switches. This gain loss can be minimized by providing a separate voltage divider network for each level of gain.

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