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5-5. Amplifier Performance Evaluation Using Square Waves
The standard sinewave frequency reopens curves do not give a full evaluation of
the amplifier transient response. the square wave, because of the high harmonic
content, yields much information regarding amplifier performance when used in
conjunction with an oscilloscope.
A. Use the test set-up of FIG 7. The 50
:
termination at the amplifier input is
essential when using square waves to eliminate the ringing effects generated
by the fast rise times.
B. Using the triangle output, set the AMPLITUDE control so that there is no signal
clipping over the range of frequencies to be used.
C. Select the square wave output and adjust the frequency to several check
points within the pass band of the amplifier such as 20 Hz, 1000 Hz and 10
KHz.
D. At each frequency checkpoint, the waveform obtained at the amplifier output
provides information regarding amplifier performance with respect to the
frequency of square wave input. FIG 7. indicates the possible waveforms
obtained at the amplifier output. Square wave evaluation is not practical for
narrow-band amplifiers. The restricted bandwidth of the amplifier cannot
reproduce all frequency components of the square wave in the proper phase
and amplitude relationships.
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