Free Circuit Diagram

Unlike the 10-band graphic equalizer in our previous circuit that use a gyrator circuit, this 3-band graphic equalizer circuit uses Baxandall topology, similar with the Baxandall tone control but with additional mid frequency control. The figure below shows the schematic diagram of the circuit. The operational amplifier employ an LF351 IC chip, but [...]

Using a special purpose single IC chip LA3600, we can build a graphic equalizer with low components count.  The internal design of the chip uses transistors gyrator circuit, with connections to external capacitors to set the response. This graphic equalizer circuit is suitable for tape-recorders, radio-cassette recorders, car stereos, or home theater sound systems. You [...]

Graphic equalizer is a filter which it’s overal frequency response can be adjusted easily by sliding the potentiometer knob, and the potentiometer’s knob positions will naturally mimic the frequency response of the filter, and this is very user friendly. Many methods have been developed by electronic engineers to make audio equalizer, such as Baxandall’s [...]

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 [...]

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 [...]

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  [...]