Abstract: In an integrated circuit in which an output transistor connected between an output terminal and a point of reference potential normally conducts current in one direction between the output terminal and the reference point and in which a potential may be developed at the output terminal causing a reverse current (i.e. one of opposite direction to the one direction) between the reference and the output terminal through the substrate, circuitry is coupled to the output terminal which is responsive to values of reverse potential at the output terminal for providing a control current at the output terminal and for holding its voltage at a value which limits the flow of reverse current.

Abstract: A class D power amplifier employing two N-channel field-effect power transistors includes an arrangement which develops a biasing voltage for the upper N-channel transistor. The biasing voltage exceeds the magnitude of the power source voltage so that the upper N-channel transistor can exhibit low channel ON resistance whereby substantially the entire supply voltage is applied to a load device. A transistor switch becomes conductive across a resistance which couples biasing voltage to the upper N-channel transistor when the biasing voltage exceeds the supply voltage.

Abstract: A current amplifier having a gain factor substantially independent of the common emitter forward current gain (beta) of its component transistors uses a cascade arrangement of current mirror amplifiers (CMA's) to compensate for variations in beta. The output of a first CMA, which current transfer ratio thereof decreases as beta decreases, is connected to the input of a second CMA, which current transfer ratio thereof increases as beta decreases. The composite current gain of the combined first and second CMA's therefore tends to remain constant as the respective betas vary.

Abstract: A protection circuit which may be used, for example, in an audio amplifier to protect the output drive transistor against conditions of excessive power dissipation. The circuit includes apparatus for monitoring the product of output current and output voltage across the protected transistor and applying a feedback signal to reduce the power dissipation if a predetermined limit is exceeded. Specifically, a representation of the product of the output voltage and output current is obtained by providing a current proportional to each and passing such current through a respective semiconductor junction to produce a logarithmically related voltage. The logarithm of the power product is obtained by summing the logarithmic voltages developed across each respective semiconductor junction.

Abstract: A protected transistor in an electronic circuit receives base drive current and has its collector-emitter path coupled to a source of collector-emitter potential and to a load. Overcurrent protection therefor is provided by a first, complementary conductivity type transistor connected base to emitter and emitter to base with the protected transistor, and thermally coupled thereto, to develop a collector current responsive to the collector-emitter current of the protected transistor. A comparator provides an overcurrent indication whenever the collector current of the first transistor exceeds a predetermined level. The overcurrent indication prevents further increase in the base drive current to the protected transistor. A further feature of the invention reduces the predetermined level in response to increasing collector-emitter potential of the protected transistor.

Abstract: Within current scaling circuitry having bipolar transistors of the same conductivity type disposed in principal master and slave paths, the negative feedback current gain around the principal master path transistor is regulated in direct proportion with the level of a current source that is independent from both of the principal master and slave paths, to substantially achieve tracking between the level of the current source and the levels of current flow through the principal master and slave paths.

Abstract: No current sensing resistor is used for sensing overcurrent condition in a power transistor in the disclosed overcurrent protection circuit, avoiding the power loss and reduction of available output potential range for the power transistor associated with the use of such sensing resistor. Instead, a differential comparator means is used to sense when the emitter-to-base potential of the power transistor exceeds that of a reference transistor sufficiently to indicate an overcurrent condition in the power transistor.

Abstract: An RC oscillator comprising an amplifier with a first RC voltage divider coupling its output circuit to its non-inverting input circuit and a second RC voltage divider coupling its non-inverting input circuit to its inverting input circuit. The first RC voltage divider comprises a series RC network in its series arm and parallel RC network in its shunt leg. The second RC voltage divider has a capacitor in its series arm and a resistor in its shunt leg.

Abstract: An output transistor in common-emitter amplifier configuration is thermally coupled to means for generating a temperature-compensated component of bias potential. This bias potential is indirectly applied to the base electrode of the output transistor to provide for temperature-stabilized idling current flow in its collector-to-emitter path. More particularly, the bias potential is applied to the non-inverting terminal of a high-gain differential-input amplifier having its output terminal direct coupled to the base of the transistor and direct coupled to its inverting input terminal for regulating the quiescent potential at its output terminal to equal the bias potential. The differential-input amplifier has an input signal applied to one of its input terminals. In response to signal excursions in one sense, the differential-input amplifier drives the output transistor into increased conduction.

Abstract: The collectors of a pair of transistors operated quasi-linearly in push-pull are coupled to their load by an autotransformer winding, center-tapped to receive operating potential. The configuration simulates a full-bridge amplifier with operating potential twice as large, insofar as maximum output power capability is concerned.