Free Circuit Diagram

This is Operational an Amplifier (Op-Amp) Oscillator circuit. This circuit has some advantages, they are this circuit can be operated at low frequencies with relatively small capacitors, it has a completely-symmetrical output waveform along with a buffered output and it will always self start and cannot hang up because there is less dc positive feedback [...]

This PWM motor control circuit provides many controls for DC motor. You can control the DC motor to rotate forward, reverse, or break until it stops. Here is the schematic diagram of the circuit: The circuit uses MOSFETS bridge to drive the motor, controlled by some logic gates and small bipolar transistors. The [...]

This circuit is a simple crystal oscillator that can be operated in overtone mode. Overtone mode permit the operation at higher frequency than specified by the crystal. The circuit uses a grounded base amplifier configuration, and place the crystal as a series resonator. The transistor Q1 is biased in the active region as [...]

This circuit is not a voice operated switch (VOX) because this circuit is too dumb to differentiate between musical sound or human voice. This is rather a sound activated than voice activated. One interesting application is to control your disco lighting automatically by the musical sound from high power amplifier, when the music signal is [...]

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 [...]

By detecting a voltage drop in resistor connected in series with the battery, we can measure the current flowing in or out  of the battery. A simple differential amplifier do that, but we need both positive supply and negative supply to sense the current in both direction,  the current when charging and discharging the battery. [...]