Archive for the ‘Signal Generators’ Category

Voltage Controlled Oscillator

VCO (Voltage controlled oscillator). Voltage controlled oscillator is a type of oscillator where the frequency of the output oscillations can be varied by varying the amplitude of an input voltage signal.Voltage controlled oscillators are commonly used in frequency (FM), pulse (PM) modulators and phase locked loops (PLL). Another application of the voltage controlled oscillator is the variable frequency signal generator itself.Block diagram of a typical voltage controlled oscillator is shown below. Voltage controlled oscillators can be broadly classified into linear voltage controlled oscillators and relaxation type voltage controlled oscillators. Linear voltage controlled oscillators are generally used to produce a sine…

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Function Generators

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…

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PUT Controlled Sawtooth Wave Generator

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…

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Sawtooth Wave Generator

Sawtooth wave generator. Many people often get confused between sawtooth wave and a triangular wave. Sawtooth waveform is a type of linear non sinusoidal waveform with a triangular shape in which the rise time and fall time are different. A pure triangular waveform is is also linear, non sinusoidal and have a triangular shape but it has equal rise and fall times.The sawtooth waveform can also be called an assymmetric triangular wave. The graphical representation of a triangular and sawtooth waveform are shown in the figure below. T1 is assumed to be the rise time and T2 is assumed to…

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Triangular waveform using Schmitt Trigger

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….

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Triangular Wave Generator

Triangular wave generator using opamp. This article is about a triangular wave generator using opamp IC. Triangular wave is a periodic, non-sinusoidal waveform with a triangular shape. People often get confused between triangle and sawtooth waves. The most important feature of a triangular wave is that it has equal rise and fall times while a sawtooth wave has un-equal rise and fall times. The applications of triangular wave include sampling circuits, thyristor firing circuits, frequency generator circuits, tone generator circuits etc. There are many methods for generating triangular waves but here we focus on method using opamps. This circuit is…

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Schmitt Trigger using Op-Amp

Schmitt Trigger or Regenerative Comparator Circuit A Schmitt trigger circuit is also called a regenerative comparator circuit. The circuit is designed with a positive feedback and hence will have a regenerative action which will make the output switch levels. Also, the use of positive voltage feedback instead of a negative feedback, aids the feedback voltage to the input voltage, instead of opposing it. The use of a regenerative circuit is to remove the difficulties in a zero-crossing detector circuit due to low frequency signals and input noise voltages. Shown below is the circuit diagram of a Schmitt trigger. It is…

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Pulse Generator using Op-Amp

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…

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Square Wave Generator using Op-Amp

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…

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Zero Crossing Detector using IC 311

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…

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