An amplifier circuit that uses multiple power supplies includes a class D amplifier circuit, input bias generator and feedback network. By creating a voltage using the input bias generator at the non inverting terminal of the integrator, the inverting terminal of the integrator will follow the same voltage as the non inverting terminal. The offset voltage between the input signal DC bias and the input DC bias of the integrator will create an offset current flowing through the feedback resistors, thus resulting in the desired output DC bias.

A drive signal that matches the bias of a transistor is generated. A differential amplifier calculates the difference between a specified voltage of negative power supply and another input signal. Then, a resistor that realizes a pull-down function level-shifts it towards a negative power supply voltage having a higher absolute voltage value to generate another differential signal, which is in turn amplified in another amplifier, to generate another drive signal that matches the bias of another transistor. Respective current mirror circuits detect a falling voltage occurring at both ends of a resistor connected between the transistor and the higher positive power supply voltage and a falling voltage occurring at both ends of a resistor connected between the other transistor and the higher negative power supply voltage, respectively. Then, the presence of an excessive electric current is detected by generating electric currents in accordance with to the falling voltages.

The class D amplifier comprises a differential signal output unit for outputting differential signals from voice signals which are input from the input terminal, and the P-side and the N-side charge balanced type class D amplifiers to which the differential signals are output. Each charge balanced type class D amplifier comprises a PWM waveform generation circuit which is comprised of an integrating amplifier and a Schmitt trigger circuit, a level shift circuit for shifting the level of the PWM signals, an output buffer for amplifying the level-shifted signals, and a feedback circuit for feeding back the output of the output buffer negatively to the integrating amplifier. The feedback circuit is constructed such that the feedback amount is variable depending on HIGH or LOW of the output of the output buffer by selecting a predetermined resistance depending on HIGH or LOW.

A processor, a circuit and a method for processing images in an analog parallel processor network. A processor comprises a plurality of circuits, a bias transistor and an output transistor. A circuit comprises a first transistor and a second transistor, which receive respective supply voltages and operate as current sources, providing an output voltage. A circuit further comprises a coefficient coupling, which receives the output voltage provided by the first transistor and the second transistor, providing a switching function for a circuit output current. A transistor in a coefficient coupling determines a mode of operation based on the output voltage, provided by the first transistor and the second transistor, and an input current. The circuit provides an output current of the circuit for further processing.

An audio preamplifier (10) based on an operational transconductance amplifier, in combination with a class D audio output amplifier (12) is disclosed. The input signal is coupled to the preamplifier (10) through a capacitor (14) in series with a resistor (17) that sets the transconductance of the preamplifier. The preamplifier (10) includes a differential operational amplifier (20) that drives output MOS transistors (22a, 22b), which are biased by current sources (24a, 26a; 24b, 26b). Feedback from the drain nodes of the output MOS transistors (22a, 22b) to the inputs of the differential operational amplifier (20), along with the series capacitor (14) and resistor (17) input coupling, ensures minimum offset voltage and current at the output of the preamplifier (10). Common mode feedback control amplifiers (25, 29) ensure proper bias of the components into the saturation region.