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Highly sensitive wireless Snoop device circuit

2016-11-28 13:09  
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Highly sensitive wireless Snoop device circuit
Highly sensitive wireless Snoop device circuit
The circuit is shown in the figure, it is composed of highly sensitive microphone amplifier and wireless transmitter unit, and the amplifier consisits of two op amps in quad op amp integrated circuit LM324. When the electret microphone MIC picks up weak sound signal, it will generate a signal voltage across the MIC, then the signal is amplified by pin 3 of the first stage operational amplifier after being coupled by capacitor C1, its amplification gain is more than 20 decibels, after the first-stage coupling, it is output from pin 1 and coupled by capacitor C3, then potentiometer RP control it for the second-stage amplifier by pin 5, then weak voice signal is amplified to have sufficient magnitude and sent to high - frequency transmitting circuit by coupling with C5.