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Dynamic microphone preamplifier circuit with LM387

A dynamic microphone preamplifier can be realized using LM387 integrated circuit. LM387 is a dual operational amplifier manufactured by National Semiconductor. Input impedance corresponds to 47k, it depends almost exclusively by R1. If you wish to connect a dynamic microphone with a different value, the resistance R1 can be changed. Dynamic microphone preamplifier amplification was set at 40dB. Input impedance of the amplifier where it will connect the preamplifier must be at least 100k.
Report Signal / noise depends on the passive components used. At an input voltage of 10mV, the signal / noise greater than 80dB.

Circuit Diagram: 
Dynamic microphone preamplifier schematic circuit with LM387

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