Self resonant power supply for electro-acoustical transducer

Claim 1

In a circuit for energizing by means of a motional bridge circuit an electro-acoustical transducer coupled to a load for transferring acoustic energy thereto including, a power amplifier circuit coupled to the motional bridge circuit for supplying an alternating cutrrent output for establishing a current flow to said transducer, and a feedback circuit connecting the motional bridge circuit to the power amplifier circuit for applying thereto an alternating current signal, the improvement comprising: an active filter, in said feedback circuit connected between said motional bridge circuit and said power amplifier circuit, said active filter being in a mode suppressant state; and a starting circuit coupled to said active filter for raising the Q of the active filter until it reverts from said mode suppressant state to a self-oscillating state when said alternating current signal is not present and for lowering the Q of said active filter until it reverts back to said mode suppressant state when said alternating current signal is present.