Posted by Tittu Thomas , 11/12/2012
Function or signal generator is one of the most important component used in designing electronics circuits especially for practical or experimental applications. I think you are already aware of the importance of a function generator.
However, here we are going to discuss about Signal 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 out of them are
The frequencies of all these waveforms can be adjusted from a fraction of a hertz to megahertz range. 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 these waveforms are suitable for specific applications.
All the function generators are capable of producing two different waveforms simultaneously from two different outputs. This may find helpful for certain application which requires more than one output waveforms at a time. For instance, by providing a square wave for linearity measurements in an audio system, a simultaneous sawtooth output may be used to drive the horizontal deflection amplifier of an oscilloscope, providing visual display of the measurement result.
Another important feature of some function generator is their capability of phase locking to an external signal source. 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 adjusting the phase and amplitude of the harmonics almost any waveform may be produced by the summation of the fundamental frequency generated by one signal generator and the harmonic generated by the other. The signal 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.
BLOCK DIAGRAM OF FUNCTION GENERATOR
Working of Signal generator
Here in this instrument the frequency is controlled by varying the magnitude of current that drives the integrator. It provides different types of waveforms at its output with a frequency range of 0.01 Hz to 100 kHz.
The frequency controlled voltage regulates two current supply sources. Current supply source one supplies constant current to the integrator whose output voltage rises linearly with time according to the output signal voltage. An increase or decrease in the current increase or reduce the slope of the output voltage and thus controls the frequency.
The voltage comparator multivibrator changes state at a predetermined maximum level, of the integrator output voltage. This change cuts off the current supply from source 1 and switches to supply source 2. The current supply 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 its state and switches on to the current supply source 1.
- The output of the integrator 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.