This is an electronic stethoscope circuit diagram. The operation of the circuit is very simple. It's work is similar to general home audio system. The heartbeat sounds catched by electret microphone and then the amplifier amplify the signal. Component List: R1 = 10K 1/4W R2 = 2.2K 1/4W R3, R9 = Not used R4 = 47K 1/4W R5, R6, R7 = 33K 1/4W R8 56K = 1/4W R10 = 4.7K 1/4W R11 = 2.2K to 10K audio -taper (logarithmic) volume control R12 = 330K 1/4W R13, R15, R16 = 1K 1/4W R14 = 3.9 Ohm 1/4W C1, C8 = 470uF/16V Electrolytic Capacitor C2 = 4.7uF/16V Electrolytic Capacitor C3, C4 = 0.047uF/50V Metalized plastic-film Capacitor C5 = 0.1uF/50V Ceramic disc Capacitor C6, C7 = 1000uF/16V Electrolytic Capacitor U1 = TL072 Low-noise, dual opamp U2, U3 = Not used U4 = 741 opamp U5 = LM386 1/4W power amp MIC = Two-wire Electret Microphone J1 = 1/8" Stereo Headphones Jack LED = Red/green 2-wire LED Batt1, Batt2 = 9V Alkaline Battery SW 2-pole, single throw Power Switch Misc. Stethoscope head or ...