National Semiconductor Corporation

Michael E Wright

Dennis M Monticelli

Robert S Sleeth

A novel circuit is taught to provide a smooth current transfer function over a range of two input voltages, so that power can be supplied to an electronic circuit from more than a single power source. In one embodiment such power sources include a battery and an DC supply operated off the AC mains. Associated with each such supply is a current source designed to provide a reference current. This reference current is used to establish mirror currents from each of the power leads in order to provide the desired output current.

Current source whose output increases as control voltages are balanced

A technique for operating a common emitter circuit from a plurality of supply voltages. In one embodiment, a current mirror includes a plurality of diode-connected transistors each connected between a source of current and associated supply voltages. Corresponding current mirrors are each connected between an output terminal associated supply voltage leads, thereby providing an output current mirrored from the soure of current, regardless of which of the supply voltages are activated, and regardless of their particular levels. In another embodiment, a regulator includes an output transistor having a plurality of current handling terminals, each connected to an associated supply voltage, and a second current handling terminal coupled to an output terminal. Feedback is provided between the output and the control terminal of the output transistors, insuring a regulated output regardless of which of the supply voltages are active at any given time, and without regard to the specific levels of the plurality of supply voltages. The feedback is provided by a differential input amplifier, or the like, and can derive its supply voltage from a plurality of supply leads utilizing a diode OR connection in order to insure that suitable feedback supply is provided regardless of the levels of the various supply voltages. In another embodiemnt, an operational amplifier circuit includes pull up and pull down output transistors, having their collectors connected to the output terminal, and one of a plurality of emitters connected to one of a plurality of positive supply voltages and negative supply voltages, respectively.

Common emitter amplifiers operating from a multiplicity of power supplies

A Safe Operating Area (SOA) circuit is constructed including a synthetic large value resistor that is an active current source whose output current is related to the power supply voltage, and whose absolute value may be arbitrarily low. A piece-wise current source is provided which includes means for generating one or more control voltages in order to control the level of output current in response to the input voltage. In one embodiment, each of the control signal means includes feedback means and a summing node, so that one or more functions are performed using a control signal as an input, with the result fed back to the summing node. In this manner, a complex function can easily be provided for controlling the magnitude of the output current. In one embodiment, the one or more control signals are provided by one or more saturating current mirrors in order to limit the output current made available. The saturating current mirror comprises a bipolar transistor having a plurality of collectors, one of the collectors serving to provide the output current, and one or more collectors connected to circuit elements which have current characteristics with respect to the input voltage. In another embodiment, the bipolar transistor having a plurality of collectors is replaced by a plurality of MOS transistors, having channel widths of desired ratios in order to provide a desired transfer function.

Piece-wise current source whose output falls as control voltage rises

Current mode logic configuration circuits are shown for use with linear integrated circuit chips. The circuits employ plural collector lateral transistors to provide logic current source outputs in response to logic current inputs that are accepted by NPN transistor current mirrors acting as current sinks. Conventional logic functions are detailed and a toggle flip-flop configuration is shown being composed of the basic logic gates. Since the disclosed current mode voltage swings are small the circuit speed is relatively high at a given shunt capacitance. Die surface area is low with many transistors sharing common n-epitaxial tubs.

Area-efficient low-power bipolar current-mode logic

A level and edge sensitive input circuit can recognize a variety of types of input signals on an input line and provide a standard digital logic output for use within the equipment. The input circuit is formed from a bias circuit, two comparators, and a memory bit. The bias circuit applies a bias voltage to the input line. A first comparator inverts the state of the memory bit when the input signals are an increment above the bias voltage. The second comparator clears the state of the memory bit when the input signals are an increment below the bias voltage. In this way, the memory bit cycles through states which provide the desired output signals for use within the equipment.

Level and edge sensitive input circuit

A Darlington output stage is shown in which the saturation voltage is reduced to the level of a single common emitter output transistor. The circuit includes a lateral feed-forward transistor that bridges the driver transistor. A resistor is included to ensure that the driver transistor is turned off when the output transistor saturates. An IC version of the circuit is set forth in detail.

Feed forward darlington circuit with reduced NPN reverse beta sensitivity

A carrier current receiver employs a comparator driven differentially to square a received data signal. The same drive signal is applied to a sample and hold circuit in which a capacitor is charged to a level that is related to the data signal offset. A voltage-to-current converter responds to the capacitor charge and feeds a current to the input where it acts to correct the offset.

Growing community of inventors

Berkeley, CA, United States of America

Michael E Wright