Importance

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Abstract

A balanced bridge (full or half) power transconductance amplifier utilizes an input voltage signal to control current converter, in the form of a differential circuit, to derive a pair of control currents representative of the input signal and a load current monitoring signal. The converter includes a current input terminal which responds to a current representative of the load impedance for reducing the amplitude of the control currents (and the bridge current) due to an impermissibly low load impedance. A class A to class B converter responds to the control currents to provide a pair of discontinuous bridge drive currents with each drive current being proportional to the difference in the control currents during respective half cycles. A differential amplifier steers the bridge drive currents to respective legs of a full bridge in response to the voltages across the power supply terminal and the load to reduce any bridge unbalance. A reactive load control circuit in the form of a differential transistor circuit is coupled to the differential amplifier to disable an appropriate leg of the bridge and effectively disconnect the power supply when the polarity of the load current is opposite to the polarity of the load voltage. An operational (error) amplifier may be coupled to the input of the transconductance amplifier to form a composite voltage amplifier with circuitry limiting the gain of the operational amplifier at high frequencies and/or limiting the excursion of the input signal to minimize the effects of clipping.

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First Claim