Frequency-independent analogue phase-shift network technique using field effect transistors

A frequency-independent phase-shift network has been designed and constructed using field effect transistors as variable resistors. The operation of the system is shown to be similar to that of a phase lock loop with a self-generating v.c.o. Analysis of the system is given assuming linear operation. Phase difference outputs have been obtained in the frequency range 20¿80 kHz. The phase error introduced in any set phase difference is ±2° in this frequency range. Theoretical predictions indicate this error could be reduced by an order of magnitude.