LOW_VOLTAGE_MICROPHONE_PREAMP

Published:2009/6/18 22:41:00 Author:May | From:SeekIC

A microphone amplifier is shown. The refer-ence, with a 500-kHz unity-gain bandwidth, is used as a preamplifier with a gain of 100. Its out-put is fed through a gain-control potentiometer to the op amp, which is connected for a gain of 10. The combination gives a 60-dB gain with a 10-kHz bandwidth, unloaded, and 5 kHz loaded at 500Ω. Input impedance is 10 kΩ.Potentially, using the reference as a preampli-fier in this fashion can cause excess noise. How-ever, because the reference voltage is low, the noise contribution, which adds root-mean-square, is likewise low. The input noise voltage in this con-nection is 440-500 nV Hz, about equal to that of the op amp.



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