Low Voltage Microphone Preamplifier Circuit

This is a low voltage microphone preamplifier circuit with a 1. 5V power supply. The reference, with a 500 kHz unity-gain bandwidth, is used as a preamplifier with a gain of 100. Its output 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, unlo

aded, and 5 kHz loaded at 500 ©. Input impedance is 10 k ©. Potentially, using the reference as a preamplifier in this fashion can cause excess noise. However, because the reference voltage is low, the nose contribution, which adds root-mean-square, is likewise low. The input noise voltage in this connection is 440-500 nV Hz, about equal to that of the amp.

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