Programming instructions

Source Components
Multisim Component Reference Guide 1-32 ni.com
1.32.1 Investigations
Sine wave
The slope of a sine wave changes continuously and smoothly. Therefore, the differentiator
output should follow the sine shape.
In the example circuit shown below, if you change frequency from 10Hz. to 100Hz., the rate
of change of the waveform will increase by a factor of 10. The differentiator output will also
increase by the same factor. When investigating, note also a 90 degree phase shift from input
to output.
Triangle waveforms
In an ideal triangle waveform the rising and falling slopes are constant with an abrupt change
taking place at the peaks.
Since the rate of change (slope) during rise and fall are constant, the differential result is also
constant.
The reversal of slope at the peaks (from rise to fall/fall to rise) produces a large instantaneous
change in the differentiator output, resulting in a square wave output.
In the example circuit, as for the sine wave, if you change frequency from 10Hz. to 100Hz.,
the rate of change of the waveform will increase by a factor of 10. The differentiator output
will also increase by the same factor.
Square waves
In an ideal square wave, the change takes place only at the rising and falling edges. The
change is instantaneous. This instantaneous rate of change
(dV/dT = dV/0)
will produce an infinitely large output from a differentiator.
Since ideal square or pulse waveforms, as produced by the function generator in Multisim,
have zero rise and fall times, the result of differentiation is infinite (dV/0 = infinity).
In the example circuit, outputs from the differentiator are limited to +/-5 kilo volts. With the
ideal square wave input, the differentiator output will be seen to be +/-5kV.
All real square wave and pulse signals have finite rise times, however small.
To introduce finite rise and fall times into the input to the differentiator, in order to investigate
realistic situations, use an RC network placed in series with the function generator.
Note Since the rise and fall times are fixed, the differentiator output does not change with
change of input frequency as for the sine and triangle waveforms.
ComponentRef.book Page 32 Thursday, December 7, 2006 10:12 AM