Preamplifier for ECM Microphone

Published:2013/3/15 4:22:00 Author:Ecco | Keyword: Preamplifier , ECM Microphone | From:SeekIC

A microphone amplifier that may be used with either Electret Condenser Microphone (ECM) inserts or dynamic inserts, made with discrete components. Both transistors should be low noise types. In the original circuit, is used BC650C which is an ultra low noise device. These transistors are now hard to find but BC549C or BC109C are a good replacement. The circuit is self stabilizing and will set its quiescent point at roughly half the supply voltage at the emitter of Q2. This allows maximum output voltage swing and also the highest dynamic range. The electret condenser microphone (ECM) contains a very sensitive microphone element and an internal FET preamp, a power supply in the range 2 to 10 volts DC is therefore necessary. Suitable ECM’s may be obtained from Maplin Electronics. Although the schematic is drawn showing a three terminal ECM, two terminal ECM’s may be used, the following page in the practical section shows the changes.



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