Function Generator
The function generator is a versatile instrument that gives a
number of different waveforms at the output with their frequencies that can be
adjusted over a wide range. The most commonly used waveforms are sine wave,
square wave, triangular wave and the saw tooth wave. Different output signals
from the function generator may be available simultaneously.
Picture of Function Generator
The fig shows the block diagram of a function generator. Here
two constant current sources are used to feed the integrator circuit. When the
circuit is switched ON, the upper constant current source sends a constant
current into the integrator and the output of the integrator is connected to
comparator.
When the integrator output reaches a predetermined level, the
comparator changes the state i.e. the upper constant current source is cut OFF
while the lower source is switched ON. This current source passes a current in
the reverse direction and the voltage at the integrator output decreases to a
pre-determined level, again the comparator switches ON, the lower current
source is switched OFF and the upper is switched ON and the cycle repeats.
The rate of rise/fall of the integrator output depends upon
the magnitude of the current supplied by the upper/lower constant current
sources. This change in the magnitudes of these currents would change the
integrator output. Frequency control network controls the magnitudes of the
current sources and hence the frequency of the output.
The integrator output is of triangular waveform which may be
amplified by the output amplifier and obtained at the output which is shown in
fig. the comparator output which is used to switch over function of the current
source is of square wave shape. This square wave output may be amplified and
used as a square wave output. Lastly the triangular diode wave shaping circuit
which converts this triangular signal into a sinusoidal signal.
No comments:
Post a Comment