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Built around a single
8038 waveform generator IC, this circuit produces sine, square or
triangle waves from 20Hz to 200kHz in four switched ranges. There
are both high and low level outputs which may be adjusted with the
level control. This project makes a useful addition to any
hobbyists workbench as well.
Allof the waveform generation is produced by IC1. This versatile
IC even has a sweep input, but is not used in this circuit. The IC
contains an internal squarewave oscillator, the frequency of which
is controlled by timing capacitors C1 - C4 and the 10k
potentiometer. The tolerance of the capacitors should be 10% or
better for stability. The squarewave is differentiated to produce
a triangular wave, which in turn is shaped to produce a sine wave.
All this is done internally, with a minimum of external
components. The purity of the sine wave is adjusted by the two
100k preset resistors.
The wave shape switch is a single pole 3 way rotary switch, the
wiper arm selects the wave shape and is connected to a 10k
potentiometer which controls the amplitude of all waveforms. IC2
is an LF351 op-amp wired as a standard direct coupled
non-inverting buffer, providing isolation between the waveform
generator, and also increasing output current. The 2.2k and 47 ohm
resistors form the output attenuator. At the high output, the
maximum amplitude is about 8V pk-pk with the square wave. The
maximum for the triangle and sine waves is around 6V and 4V
respectively. The low amplitude controls is useful for testing
amplifiers, as amplitudes of 20mV and 50mV are easily achievable.
The two 100k preset resistors adjust the purity of the sine wave.
If adjusted correctly, then the distortion amounts to less than