Circuit and method for adjusting the bias of an amplifier based upon load current and operating temperature

摘要

An electronic circuit for automatically adjusting the operating point of an audio amplifier comprising means for sensing the current flowing in the load, coupled to a first threshold detector, said first threshold detector having a plurality of outputs, each of said outputs representing some fraction of maximum load current; a plurality of timing means, each triggered by one of the plurality of outputs from said first threshold detector, each having a time constant inversely proportional to the fraction of load current represented; means for sensing the operating temperature of the amplifier output stage devices, coupled to a second threshold detector, said second threshold detector having an output which is enabled above a certain temperature and where said output may be used to inhibit one or more of the timer means; means for detecting bias level in a pre-driver stage, coupled to a low pass filter; a error amplifier, whose inputs are coupled to said temperature sense means, said timer outputs and said low pass filter, and whose output is then coupled to the input of said audio amplifier to effect the change in bias.