A new low cost, high performance audio power amplifier topology that uses current-feedback in the main gain stage is described. This technique, which has previously been restricted mainly to wideband and video amplifier circuit design, improves on the more common, voltage-feedback amplifier topology by providing a wide closed-loop bandwidth relatively independent of gain, and very high slew-rates. Measurements on the prototype power amplifier show that a closed-loop bandwidth of 1 MHz, at a gain of 24, and slew-rates in excess of 200 V/µs are readily achievable with inexpensive off-the-shelf components. In addition, the in-band harmonic distortion is quite low (<0.002% at 1kHz), due to the large loop gain that is achievable at audio frequencies.
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