Producing 180/spl deg/ out-of-phase signals from a sinusoidal waveform input

In this paper a simple and novel method for producing two signals with 180/spl deg/ phase difference has been introduced. The phase-balanced signals are produced from a single sinusoidal input signal using two matched op-amps. The phase accuracy of the proposed circuit due to mismatched components is investigated with a two-pole model for the operational amplifiers. With high-precision integrated circuits, the phase error at the amplifier pole frequency a (2 MHz) is calculated to be about 0.5/spl deg/ which is a remarkable achievement. The discrete implementation of this scheme is also discussed, and there is a good agreement between the experimental results and the calculated values. The main features of this circuit make it suitable for use in bridge measuring systems and lock-in amplifiers.