Precision phase shifters for processing sinusoidal signals are described. The proposed circuits are capable of extremely low phase errors and in the case of a 120° design could, for example, maintain a phase constancy of ±0.015 degrees in the face of variations in frequency of ±5% about the central design value. The effects of limited amplifier bandwidth on the phase responses are examined and alternative design strategies with reduced gain bandwidth dependence are suggested. An economical quadrature phase shifting network is also presented, together with a simple phase-error compensation arrangement.