Improved Design of Three-Stage RC Phase Shift Oscillation Circuit

Three-stage RC phase shift oscillation circuit is common as a low-frequency oscillation circuit for its low cost and high stability. Due to the output impendence of the operation amplifier or transistor and resistance or capacitor tolerance, the actual oscillation frequency deviates from the theoretical frequency. The voltage gain is difficult to calculate as it shows temperature drifts especially in the transistor oscillation circuit. Thus, we analyzed the causes of the errors and instability and then proposed a correction method based on the amplifier. A theoretical feasibility analysis was provided for the actual oscillation circuit design. This method reduced oscillation frequency errors to 1/6. The improved oscillation circuit voltage gain was decided only by the ratio of two resistances, and the temperature drift was reduced significantly showing high stable gain stability.