Simple Electronic Stethoscope circuit

This is an electronic Stethoscope circuit. Usually, the stethoscope is a medical device that listens to the heartbeat.

It is very useful. Do you believe it? We can try to create it. With a simple electronic circuit.

Simple Electronic Stethoscope circuit
Simple Electronic Stethoscope circuit


Which we can make it with principle working looks like a preamplifier circuit. So, easy to make.

Learn also: High impedance preamplifier using a transistor

How it works

See the block diagram below.

We use piezo speakers as a microphone. This is transducer can power output signal up to 100mV at the low-frequency response. This signal is very tiny.

Block diagram of Simple Electronic Stethoscope circuit

So, we need to use a high-impedance input impedance preamplifier to increase the signal up. To drive a headphone output.

Recommended: Hi-Fi headphone Amplifier circuit

What is more? See the simple circuit below.

High impedance preamplifier using a transistor
High impedance preamplifier using a transistor

This is simple high impedance preamplifier using only one transistor. Is it easy? Yes. We can modify just a little to better. See below.

Electronic Stethoscope circuits

Electronic Stethoscope circuit

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Here is step-by-step a process.

The piezo speaker(PZ1) will detect the heartbeats. Then, the signal comes to a signal amplifier that consists of Q1, in combination with R1-R4, VR1, and C1.

Some called it that a common-emitter amplifier. The input and output signals both share a connection to the emitter.

It can output response with low frequencies. So the output is connected to the headset with low impedance.

To be able to listen to the heartbeat. The VR1 will act as a volume adjuster to loud or low.

We can use the Darlington transistor to increase the input impedance of the amplifier.

Parts will you need

Resistors 0.25W, tolerance: 5%
R1: 10K
R2: 330K
R3: 100K
R4: 47K
VR1: 220K Linear Potentiometer

C2: 10µF 25V, Electrolytic Capacitors
C1: 0.1uF 50V, Ceramic Capacitors

Semiconductor and others
Q1: BC548, BC547, BC549, 45V 100mA NPN Transistor
PZ1: piezo speaker
B1: 9 volts battery
Universal PCB

Check out these related Circuits, too:


I always try to make Electronics Learning Easy.

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