Patent ID: 7288993

Claim:
An amplifier circuit, comprising: first and second power supply rails, said first rail being positive with respect to said second rail; and first and second parallel-connected output stages, said first output stage comprising: a small signal amplifier connected between said rails which receives first and second input signals applied to respective input nodes and provides an output signal at an output node suitable for driving a load, said small signal amplifier arranged such that said output signal varies approximately linearly with the difference voltage between said input signals when said difference voltage is less than a predetermined threshold; said second output stage comprising: a large signal output boost stage connected directly to said output node which, when said difference voltage is greater than said predetermined threshold, is arranged to drive said output node close to said first or second supply rail so as to provide load currents which might otherwise overload said small signal amplifier, said second output stage arranged such that it is off when said difference voltage is less than said predetermined threshold.