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With one double operational amplifier you can make a quality generator that generates
both rectangular, triangular or saw pulses. Operational amplifier in the DIL8 package
contains two independent operational amplifiers with common power supply. The first
operational amplifier in Figure 1 (yellow) is connected as a non-inverting trigger
amplifier. The second operational amplifier (blue) is involved as an integrator.
It generates the output of a non-inverting amplifier rectangular and the integrator
output generates a triangular or sawtooth waveform.
The potentiometer R10 can be used to change the sawtooth waveform via a triangular
waveform to an inverted sawtooth waveform. Potentiometer R9 changes the waveform
frequency and potentiometer R8 sets the voltage offset. The condition of the connection
function is that the resistance R2 is greater than resistor R1. The values ??of the
components in the circuit of Fig. 1 are for very low frequencies. The frequency is
given by the values C1, R5 and R9.
If we change the previous connection from Fig. 1 by inserting diodes instead of
potentiometer R9 and two potentiometers (one potentiometer and one trimmer will also
suffice) - see Fig.2, we can influence the leading edge (R9) and the falling edge (R11)
of the waveform.
The previous connection can be changed to a connection with only one potentiometer:
In both cases, potentiometer R10 controls the symmetry of the output signal.
Returning to the connection in Fig. 1, we can insert a potentiometer (R11) between
resistors R1 and R2. It must still be true that R2> R1. This potentiometer then
controls the amplitude of the signal.
All connections described above can be further modified and adjusted. For example,
we can insert into the connection another voltage source, represented by the
operational amplifier U1c (red) and connect another operational one to the output
amplifier U1b (green). We obtain a signal generator with pulse-width modulation.
To implement the connection a single integrated circuit is sufficient, a 4-way
operational amplifier in a DIL14 package.
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