National Semiconductor Corporation

Matsuro Koterasawa

Toyojiro Naokawa

An input bias cancellation stage for an audio operational amplifier is provided. The input bias cancellation stage includes an input differential pair, a current mirror, and a bias duplicator transistor that substantially duplicates the input bias current. The bias duplicator transistor receives substantially the same emitter current as the transistors in the input differential pair, and has substantially the same Vce as the transistors in the input differential pair. The current mirror mirrors the duplicated bias current and subtracts it from the bases of the transistors in the input differential pair so that the input bias current is substantially cancelled.

Apparatus and method for input stage and bias canceller for an audio operational amplifier

A circuit is shown in which a voltage regulator has an output stage that operates as a Darlington when the input-output differential exceeds a threshold. The circuit automatically switches to a common emitter output and an emitter-follower driver when the differential falls below the threshold. A current limiter prevents excessive common current when the output transistor is saturated.

Low dropout voltage regulator with low common current

A class AB monolithic silicon IC output stage is shown wherein the main output transistors are NPN structures. The current sourcing transistor is provided with an additional scaled down reference emitter and the two emitters connected to the inputs of an op amp which has its output coupled to drive the current sink transistor. The base of the current source transistor is driven from a high gain driver transistor stage which may also contain a d-c level shifter that permits the inclusion of a complementary current sink transistor that can greatly reduce cross-over distortion while conducting only quiescent current.

IC class AB amplifier output stage

A current mirror provides an output current, for use in an IC, that is a multiple of a reference current input. A high gain negative feedback loop is coupled between the current mirror reference input and the output device. This forces the reference input to operate as a diode and stabilizes the circuit operation so that the output current accurately reflects the reference current independently of the .beta. of the devices.

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Koto-ku, Japan

Matsuro Koterasawa