31-03-2017, 10:40 AM
An electronic stethoscope is used to listen to the heartbeat and is usually used a listening tube or a stethoscope. This electronic stethoscope circuit uses a piezo sounder from a musical greetings card or melody generator, like microphone. This transducer has an output signal of the order of 100 mV and its low frequency response is governed by the input impedance of the amplifier. For this reason we have chosen to use a transistor amplifier emitter followers. This has a high input impedance and ensures that the transducer will have a very low frequency response. At the output you only have to connect a set of low impedance headphones to hear your heartbeat. The replacement of the follower emitter with a Darlington transistor configuration will further increase the input impedance of the amplifier.
Circuit diagram of electronic stethoscope
Circuit diagram of electronic stethoscope
![[Image: electronic-stethoscope.jpg]](http://www.electroschematics.com/wp-content/uploads/2008/11/electronic-stethoscope.jpg)