Free Circuit Diagram

This transistor tester is very helpful if you need to sort bulk transistors. In  some market, if you know where to find it, sometimes you can get transistors sold in kg unit, not in single peaces unit. You can buy 1 kg of transistors with really cheap prices. Don’t be too happy right now because [...]

The function of this circuit is similar with the hum filter in our previous circuit, but it use transistors instead of op-amps. It uses BC109 transistors, but any low noise high gain type will be suitable. This hum filter is adjustable via trimmer pots to fine tune it’s notch depth.   The figure below shows [...]

In designing small signal amplifier circuits, to achieve a specified amplifier gain we usually use opamp amplifier design to ease the setting of the gain. When the gain accuracy is not critical, we can use transistor feedback amplifier as the base of our amplifier design. Here is the schematic diagram of the transistor amplifier: [...]

This capacitance meter circuit is similar with previous meter circuit, but it uses transistors rather than logic gates. Here is the schematic diagram: You can see the circuit uses pnp transistor, you can use almost any pnp transistors with frequency bandwidth og 100MHz and collecttor current handling capability of 100 mA to replace [...]

Testing whether a transistor is shorted or open usually done by ohm meter. You test if the base to emitter  or collector permit a current flow in one direction. Here is the circuit’s schematic diagram: The 555 timer ( IC1 ) operate as a 12hz  oscillator. The output of this oscillator (pin 3) [...]

Classic LED Flasher Circuit This LED flasher circuit is a classic two transistor flip flop. This flasher circuit is very popular and it’s usually the first circuit to build when starting electronic circuit building hobby. Here is the schematic diagram of the famous LED flasher circuit: How LED Flasher Circuit Works [...]