Chapter Four - Oscillators

Abstract

An oscillator is essentially an amplifier that produces its own input. That is, if an oscillator circuit is connected to a DC power supply, it will generate a signal without having a similar signal available as an input. One of the most fundamental ways to classify oscillator circuits is by the shape of the waveform generated. This chapter studies oscillator circuits that produce waveforms such as sinewave, rectangular wave, ramp wave, and triangular wave. It discusses various different oscillators. The first one is the Wien-bridge oscillator that produces sinewaves and uses an RC network as the frequency-determining portion of the circuit. The second one is voltage-controlled oscillator, whose frequency can be controlled or varied by a DC input voltage. Another oscillator discussed here is the variable-duty cycle. This circuit is particularly useful. The duration of each alternation is independently adjustable, which means that the duty cycle of the output can be easily adjusted from a very small to a very high value. The last oscillator described in this chapter is a triangle wave oscillator, which generates a dual ramp (triangle) output. It also provides troubleshooting tips for oscillating circuits. Finally, it concludes by listing certain non-ideal considerations regarding these circuits.