Simple Crystal Tester

Transistor Q1, a 2N3563, and its associated components form an oscillator circuit that will oscillate if, and only ...

Electronic Stethoscope

Circuit Description: U1a operates as a low-noise microphone preamp. Its gain is only about 3.9 because the high output impedance of the dr...

TDA2005 - Low Cost 2x20 Watt Stereo Amplifier

This circuit is a small stereo amplifier for all suitable applications like amplifying small speakers, boxing, etc. It is also suitable fo...

Infra-Red Remote Control Tester

This little circuit is invaluable for quick go/no-go testing of just about any remote control transmitting infra-red (IR) light. The test...

Contactless AC Mains Voltage Detector

This is a CMOS IC (CD4033) based circuit which can be used to detect presence of AC mains voltage without any electrical contact with the ...