Free Circuit Diagram

One of the interesting features of CA3130 op-amp  is its high input resistance, because using such high  input resistance, we can build an astable multivibrator with high R/C ratios. The figure below shows the circuit’s schematic diagram, you can see the variable resistors to adjust the “on” and “off” periods independently. Resistors R1and [...]

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 [...]

The simple low-pass filter is shown in Figure below. The filter has a 20dB/decade roll-off after its corner frequency fc. Its low-pass frequency gain (f->0) is defined by R3/R1. This allows low-frequency gains other than unity to be obtained.  R2 should be chosen equal to the parallel combination of R1 and R3 to minimize error [...]

This circuit is similar to our previous tone control circuit, a bass-treble tone control circuit, but here we present the formula for design your tone control’s custom frequency response. Here is the schematic diagram and formula of the tone control circuit: Almost all op-amp type can be used, as long as they have [...]

Pulse position modulator can be easily built using 555 IC. Here is the schematic diagram of the circuit: Pulse position modulator modulate the on-period while keeping the fixed off-period. Pulse position modulation might substitute pulse-width modulation in some application. The main difference between pulse position modulation (PPM)  and pulse width modulation (PWM)  is [...]