Cherry Semiconductor Corporation

Denis P Galipeau

Christopher J Sanzo

John G Metro

Jon A Rhan

A circuit for providing a temperature-compensated reference current, the circuit comprising a current mirror and a V.sub.BE multiplier circuit. The current mirror includes a reference transistor with its collector providing the temperature-compensated reference current. The V.sub.BE multiplier circuit connects together the base and collector of the reference transistor so as to provide a voltage differential in a range of values having a greatest lower bound equal to V.sub.BE, and sinks (or supplies) base current to the reference transistor so that the reference current is not appreciably affected by the base current of the reference transistor.

Temperature compensated current reference

A voltage clamp for protecting a load from transients in a supply line comprising pass transistors coupled to a bias circuit path. The bias circuit path determines the clamp turn-on voltage of the voltage clamp and comprises transistors configured as zener diodes and transistors configured as forward biased pn junctions. The pass transistors are coupled to the bias path so as to conduct current from the supply line to ground when the voltage drop across the bias circuit path reaches the clamp turn-on voltage. The collector-to-emitter voltage drops of the pass transistors during current conduction are equal to one another and sum up to the clamp turn-on voltage, and therefore, the pass transistors advantageously share equally the clamp turn-on voltage drop across their collector-to-emitter junctions. The bias circuit path is temperature compensated so that the clamp turn-on voltage is substantially independent of temperature. Additional bipolar transistors are coupled between the pass transistors and bias circuit path to supply bias current to the pass transistors so that negligible current is drawn from the bias path when the pass transistors are conducting current.

Temperature-compensated voltage clamp with forced pass transistor

A transistor overcurrent protection circuit using an error amplifier to make a voltage comparison between a threshold voltage and the collector voltage of a current sensing transistor. The current sensing transistor is arranged in a circuit such that the collector current of the current sensing transistor is a measure of the collector current of an output transistor. A driver transistor has its emitter connected to the base of the output transistor. A source of control current to the drive transistor is coupled to the output of the error amplifier. When the collector voltage of the current sense transistor falls below the threshold voltage, the error amplifier causes the control current to the drive transistor to be reduced so as to reduce the collector current of the output transistor.

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Woonsocket, RI, United States of America

Denis P Galipeau