Free Circuit Diagram

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 [...]

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 [...]

The high durability nature of a light emitting diode (LED) make it suitable for ON/OFF indicator application. Because the limitation on low operating voltage, LEDs are normally applied on low voltage application.  Fortunately, there is a simple method to apply LED indicator for high powerline voltage: reactance of a capacitor can be used to limit [...]

Capacitance meter can be very helpful in identifying old components where its mark has been erased or became unreadable. Such instrument can be quite expensive, but fortunately we can build it easily with much lower cost. The capacitance meter described here can measure any capacitor between 1pF and 10uF. Here is the schematic diagram of [...]

This is a circuit of Temperature-Compensated Capacitive Proximity Detector. it will lights the LED when a person approaches the antenna plate. Here is the circuit : The 4-inch-square antenna plate and a 33pF capacitor (C1) in parallel with 15pF (6 inches of coaxial cable at 30pF per foot)  are used to form delay [...]

These are circuits of high impedance low capacitance buffer and high impedance low capacitance  amplifier. First figure is a high impedance low capacitance buffer circuit, it uses the 2N446 JFET that features low input capacitance. The feedback buffer a wide-band unity gain amplifier is made from this 2N446 JFET. Here is the circuit : [...]