Electronic Circuits and Diagram-Electronics Projects and Design

RELATED ARTICLE SWEEP-FREQUENCY GENERATOR In most cases, the frequency of an oscillator is determined by the time constant RC. However, in cases or applications such as FM, tone generators, and frequency-shift keying (FSK), the frequency is to be controlled by means of an input voltage, called the control voltage. This can be achieved in a voltage-controlled oscillator (VCO). A VCO is a circuit that provides an oscillating output signal (typically of square-wave or triangular waveform) whose frequency can be adjusted over a range by a dc voltage. An example of a VCO is the 566 IC unit, that provides simultaneously…

A function generator is a signal source that has the capability of producing different types of waveforms as its output signal. The most common output waveforms are sine-waves, triangular waves, square waves, and sawtooth waves. The frequencies of such waveforms may be adjusted from a fraction of a hertz to several hundred kHz. Actually the function generators are very versatile instruments as they are capable of producing a wide  variety of waveforms and frequencies. In fact, each of the waveform they generate are particularly suitable for a different group of applications. The uses of sinusoidal outputs and square-wave outputs have…

A PUT controlled sawtooth generator circuit is shown in figure. When power is first applied, the programmable unijunction transistor (PUT) is off. The capacitor C begins to charge up and the output voltage rises. This continues until the output voltage (which is also the PUT anode voltage) is about 0.7 V above the control input (the gate voltage). The PUT gets switched on. The capacitor C is shorted out through PUT and, therefore, capacitor gets immediately dis­charged through the PUT. The output voltage, which is equal to the voltage across the capacitor, falls. When the current through the PUT falls…

How to make a Sawtooth Wave Generator using Op-Amp 741 IC ? Sometimes it is felt necessary to provide a relatively slow linear ramp with a rapid fall (or rise in the case of a negative ramp) at its end. This is a sawtooth wave. Also, in applications such as time base generators and power control circuits, the sawtooth must be triggered by (or be synchronized with) some control signal. The difference between the triangular and sawtooth waveforms is that in triangular waves the rise time is always equal to its fall time while the sawtooth waveforms have different rise…

How to make a Triangular waveform using Schmitt Trigger and Integrator ? Another triangular-waveform generator that needs fewer components is shown in figure. The arrangement consists of a non-inverting Schmitt trigger Ax and an integrator A2. The output of a Schmitt trigger is a rectangular wave that drives an integrator. The output of the integrator is a triangular wave, which is fed back and used to drive the Schmitt trigger. Thus first stage drives the second, and the second drives the first. But the question arises on how the circuit gets started in the first place. This is explained below….

The op-amp triangular-wave generator is another example of a relaxation oscillator. We know that the integrator output waveform will be triangular if the input to it is a square-wave. It means that a triangular-wave generator can be formed by simply cascading an integrator and a square-wave generator, as illustrated in figure. This circuit needs a dual op-amp, two capacitors, and at least five resistors. The rectangular-wave output of the square-wave generator drives the integrator which produces a triangular output waveform. The rectangular-wave swings between +Vsat and -Vsat with a time period determined from equation. The triangular-waveform has the same period…

How to make a Schmitt trigger or a Regenerative Comparator using 741 IC ? A Schmitt trigger circuit is a fast-operating voltage-level detector. When the input voltage arrives at the upper or lower trigger levels, the output changes rapidly. The circuit operates with almost any type of input waveform, and it gives a pulse-type output. The circuit of an op-amp Schmitt trigger circuit is shown in figure. The input voltage vin is applied to the inverting input terminal and the feedback voltage goes to the non-inverting terminal. This means the circuit uses positive voltage feedback instead of negative feedback, that…

How to make a Monostable Multi Vibrator using 741 IC ? As already explained , a monostable multivibrator (MMV) has one stable state and one quasi-stable state. The circuit remains in its stable state till an external triggering pulse causes a transition to the quasi-stable state. The circuit comes back to its stable state after a time period T. Thus it generates a single output pulse in response to an input pulse and is referred to as a one-shot or single shot. Monostable multivibrator circuit illustrated in figure  is obtained by modifying the astable multivibrator circuit  by connecting a diode…

How to make an Astable or Free running Multi vibrator using 741 Op-Amp ? The non-sinusoidal waveform generators are also called relaxation oscillators. The op-amp relaxation oscillator shown in figure is a square wave generator. In general, square waves are relatively easy to produce. Like the UJT relaxation oscillator, the circuit’s frequency of oscillation is dependent on the charge and discharge of a capacitor C through feedback resistor R,. The “heart” of the oscillator is an inverting op-amp comparator The compa­rator uses positive feedback that increases the gain of the amplifier. In a comparator circuit this offer two advantages. First, the high…

How to make a Zero Crossing Detector using  311 Op-Amp IC ? A zero-crossing detector using IC 311 (8 pin DIP unit) is illustrated in figure. The positive (above 0 V) going input signal drives the output transistor on, the output going low (- 10 V in this connection). The negative (below 0 V) go­ing input drives the output transistor off, the output going high (+ 10 V in this connection). The output is thus an indication of whether the input is above or below 0 V. When the input is any positive voltage (above 0 V), the output is…