An Electret Microphone Interface

Distortion Reduction with Gain

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A Ciphers By Ritter Page

Terry Ritter

2005 November 14

Introduction

An electret microphone is basically a capacitor microphone with internal bias and a JFET preamp. One problem with this configuration is that even an ideal JFET must produce some distortion. Without getting into the microphone capsule itself, which is tough to do if we want it to work again, not much can be done. But one thing that can be done is to fix the drain voltage at a constant value even under load, thus minimizing any voltage effect on the gain of the JFET. In a bipolar device, this would be called "the Early effect."

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The Build

The Fancy Schematic

Last updated: 2005-10-14