Free Circuit Diagram

Electroscope is a device that is used to detect electrostatic charges. Operation: To reduce AC noise this circuit uses C1, but it will lower the sensitivity a bit. As a voltage divider we use the MPF102 and R1. The divider’s output will be about 4.5V diving a half-scale reading on M1, a 200-uA [...]

Precision accelerometers needs inverting mode amplifier since they are usually charge-output  devices. This amplifier convert charges into voltage output. The circuit below is an example of accelerometer with DC servo. The charge from the transducer is converted to a voltage by C1, which should equal the transducer capacitance plus the input capacitance of [...]

Feedback in public address amplifier is something that should be avoided. The ideal solution is by adjusting the microphone and the speaker position, but it’s not always possible in many situation. Using frequency shifter to change the output frequency 10Hz lower than the input frequency can solve the problem, but it’s too expensive for [...]

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: [...]

The signal can be converted by piezoelectric films in many ways such as thermal to electrical (temperature sensor), mechanical to electrical (microphone), and electrical to mechanical ( a loudspeaker). The circuit is signal conditioning amplifier for piezofilm sensor which use three op amps and has a high-input-impedance differential charge. Here is the circuit : [...]

Hydrophone is similar with microphone, except that it is used in underwater environment. Off course a hydrophone can be used to pick up sound in air, but it will be less sensitive since it’s mechanical-acoustical properties is design to match the acoustical impedance of water. The schematic shows the circuit of a low [...]