Abstract: The invention teaches an amplifier (100) with an input signal (IN) coupled to the gate of a second transistor (Q2) and an output signal (OUT) coupled to an output node between a third resistor (R3) and the drain of the second transistor (Q2). A third transistor (Q3) is coupled in parallel between the output node and the gate of a second transistor (Q2). A first bias signal (Vbias) is coupled to the output node and the gate of the third transistor (Q3). The amplifier preferably also includes a plurality of switchable resistors coupled to the output node to adjust the output for process variations. The invention also describes a method of compensating for process variations in an output of an amplifier which comprises producing a reference signal dependent on the difference between a reference value and an actual value and switching one or more resistors into the output of the amplifier to adjust the output of the amplifier to reflect the process variations.

Abstract: A class D amplifier includes a noise-shaping modulator, a pulse width modulator, and a pulse amplifier. The noise-shaping modulator receive a pulse code modulated (PCM) signal and produces an oversampled PCM signal. The pulse width modulator produce a pulse width modulated (PWM) signal from the oversampled PCM signal. The pulse amplifier amplifies the PWM signal to produce an amplified PWM signal. The PWM uses a lookup table to convert from PCM to PWM. A compensation circuit optimizes amplifier performance. An optional demodulator filter converts the amplified PWM signal to an analog signal. The amplifier is ideal for integrated audio applications.