R-C tuned oscillators

Generally, a multivibrator-type oscillator is noted for its distorted output. However, sinusoidal oscifiations of good waveform can also be obtained from this system. In the present paper, the conditions for sinusoidal oscillations have been studied for both a straight-coupled and a cathode-coupled system. By proper choice of components, frequencies from a few cycles to a few Meg can be generated. The limitation of these oscillators for wide frequency variation has been overcome by evolving a new type of frequency selective network, which, when connected in the feedback path of an amplifier, can shift the frequency of oscillation of the system up and down the frequency spectrum without affecting the loop gain of the system. It can be used as an oscillator, selective amplifier, or a rejection filter at the same frequency for a given setting of the C-R value of the network. The salient feature is that the frequency can be varied by varying a single element while the necessity for using an automatic amplitude limiting device is avoided due to the fact that the transmission constant of the network is independent of frequency.