The base of this circuit is one of the four Norton amplifiers existing in an LM3900 integrated circuit. The generated signals are rectangular at a frequency of 1 kHz for the values of the components indicated in the diagram in the figure. The capacitor may have its value changed to obtain another frequency for the signal, but the upper limit does not go beyond a few hundred kilohertz. The power supply must be symmetrical with voltages from 6 to 12 volts.
