Function Generator

A Function Generator is a signal source that has the capability of producing different types of waveforms as its output signal. The sine-waves, triangular waves, square waves and sawtooth waves are some common output waveforms that can be easily produced using signal generator. The frequencies of such waveform may be adjusted from a fraction of a hertz to several hundred kHz. They are very versatile instruments as they are capable of producing a wide variety of waveforms and frequencies.

The triangular-wave and sawtooth wave outputs of function generators are commonly used for those applications which need a signal that increases (or reduces) at a specific linear rate. They are also used in driving sweep oscillators in oscilloscopes and the X-axis of X-Y recorders.

Features of Function Generator

Some of the important features of function generator which make it a prestigious instrument in CRO are discussed below

1. Generating Two Different Waveforms

Sometimes two generated signals of different waveforms are required for particular application. To perform this purpose some function generators which are capable of generating different waveforms simultaneously (from different output terminals) are used.

for example :-By providing a square wave for linearity measurements in an audio-system, a simultaneous save output may be used to drive the horizontal deflection amplifier of an oscilloscope, providing a visual display of the measurement result.

2. Generating Two Different Waveforms of Equal. Frequencies

A function gen. can also generate two different types of waveforms of equal frequencies . Example, A triangular-wave and a sine-wave of equal frequencies can be produced simultaneously. This is done when the zero crossings of both the waves are made to occur at the same time, as the result of this, a linearly varying waveform is available which can be started at the point at phase of a sine-wave.

3. Capability of Phase Locking

Some function generators also have their capability of phase locking to an external signal source. It can be understood as one function generator may be used to phase lock a second function generator and the two output signals can be displaced in phase by an adjustable amount. In addition one function generator may be phase locked to a harmonic of the sine-wave of another function generator.

By adjustment of the phase and the amplitude of the harmonics, almost any waveform may be produced by summation of the fundamental frequency generated by one function generator and the harmonic generated by the other function generator. The function generator can also be phase locked to an accurate frequency standard, and all its output waveforms will have the same frequency, stability and accuracy as the standard.

Function Generator Circuit

Working of Function Generator

The working of function generator is divided into three mode as explained below

Function of Frequency Control Network

In the frequency control network, the frequency is controlled by varying the magnitude of current that drives the integrator This instrument provides different types of waveforms (such as sinusoidal, triangular and square waves) as its output signal with a frequency range of 0.01 Hz to 100 kHz.

Function of Current Supply Sources

The frequency controlled voltage regulates two current supply sources Current supply source 1 supplies constant current to the integrator whose output voltage rises linearly with time. An increase or decrease in the current increases or reduces the slope of the output voltage and thus controls the frequency.

Function of Voltage Comparator Multi-vibrator

The voltage comparator multi-vibrator changes state at a predetermined maximum level of the integrator output voltage. This change cuts-off the current supply from supply source 1 and switches to the supply source 2. The current supply source 2 supplies a reverse current to the integrator so that its output drops linearly with time. When the output attains a predetermined level, the voltage comparator again changes state and switches on to the current supply source.

The output of the integrate is a triangular wave whose frequency depends on the current supplied by the constant current supply sources. The comparator output provides a square wave of the same frequency as output. The resistance diode network changes the slope of the triangular wave as its amplitude changes and produces a sinusoidal wave with less than 1% distortion.

Frequently Asked Questions (FAQs)

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