Free Circuit Diagram

Using a single supply quad comparator LM339, LM239, LM2901, LM2901V, NCV2901, or MC3302, we can build a square-wave oscillator with simple circuit and formula. Here is the schematic diagram: This circuit is suitable if you need  many square-wave oscillators in one circuit, since the quad packaged comparator provide four comparators in one single  [...]

The excellent high input impedance, high slew rate, and high voltage qualities of CA3140 op-amp make it suitable for Wien-bridge sine wave oscillator. The basic circuit for Wien-bridge sine wave oscillator is shown in the figure below (the upper part). You can see the formula in the figure, when R1=R2=R, and C1=C2=C, then the formula [...]

With very low harmonic distortion, 2N4416 JFET is suitable to smoothly oscillate in a circuit. On application where low harmonic content is required for a good mixer circuit, JFET local oscillator is very good. Below is the circuit diagram of Low Distortion Oscillator: And here’s the 20 MHz Oscillator Values [...]

This circuit is another radio frequency (rf) field strength meter, similar with our previous field strength meter circuit, but with lower supply voltage (only a single cell 1.5V battery). Here is the schematic diagram of this rf strength meter circuit: To use, turn on transmitter and meter; adjust C1 for peak [...]

Notch filter is known as band-cut filter or band-reject filter. The fuction of this filter is to remove some frequency portion of a signal. The schematic diagram of this filter circuit, a second order notch filter is depicted in the figure below. The formula is actually complicated, but by taking the R3=R4 and [...]

Designing passive crossover network for your speaker system is easy, just like what shown in our previous crossover design article, but now we can design many types of crossover even easier using online crossover design tool. The crossover schematic diagram here is an example  with a case of 10 kHz high corner frequency, 1250 Hz  [...]