Abstract: A protective coupling circuit is located between the D.C. supply voltage the amplifier components of a push-pull switching amplifier to suppress transients created during switching. The coupling circuit comprises a power supply filter with an inductor coil and capacitor, and circuitry for limiting the voltage on the individual switching elements and the output coil. Excess voltages caused by transients are fed to the power supply filter. In an alternative embodiment the power supply filter inductor coil is actually an auxiliary winding on the amplifier output transformer rather than a separate coil. This allows for use of some smaller capacity circuit elements.

Abstract: A drive circuit responsive to the phase of the amplifier output current eres that the non-conducting amplifier element remains off while the other amplifier element conducts. The output current phase can be detected either from the individual amplifier element outputs or from their combined outputs. Adjustments are made to compensate for any phase shift which occurs between the input to the amplifier and the point in the output at which the phase is detected.