Transistor circuit with E/C voltage limiter
First Claim
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1. A circuit arrangement comprising:
- a first transistor of a first conductivity type having an emitter coupled to a first power-supply terminal, a collector coupled to an output terminal, and a base,a drive circuit for driving the first transistor, said drive circuit being coupled to a second power supply terminal and having an output coupled to the base of the first transistor, anda limiting circuit for limiting the voltage between the emitter and the collector of the first transistor to a specific value by reducing the drive to the first transistor when said voltage decreases below said specific value, wherein the limiting circuit comprises a first resistor connected between the output of the drive circuit and the base of the first transistor, and a second transistor of the first conductivity type having an emitter coupled to the collector of the first transistor, a collector coupled to a control input of the drive circuit, and a base coupled to that end of the first resistor which is situated nearest the drive circuit output.
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Abstract
In a series-regulation transistor (T1), which is driven by a drive circuit (10), for generating a constant voltage across a load (RL) the occurrence of comparatively large substrate currents in the case of saturation of the series-regulation transistor (T1) is precluded by a limiting circuit comprising a resistor (R1) arranged in the base line of the series-regulation transistor (T1) and a second transistor (T2) whose base-emitter junction is arranged across the resistor (R1) and the base-collector junction of the series-regulation transistor (T1). The collector of the second transistor is connected to a control input (12) of the drive circuit.
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Citations
14 Claims
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1. A circuit arrangement comprising:
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a first transistor of a first conductivity type having an emitter coupled to a first power-supply terminal, a collector coupled to an output terminal, and a base, a drive circuit for driving the first transistor, said drive circuit being coupled to a second power supply terminal and having an output coupled to the base of the first transistor, and a limiting circuit for limiting the voltage between the emitter and the collector of the first transistor to a specific value by reducing the drive to the first transistor when said voltage decreases below said specific value, wherein the limiting circuit comprises a first resistor connected between the output of the drive circuit and the base of the first transistor, and a second transistor of the first conductivity type having an emitter coupled to the collector of the first transistor, a collector coupled to a control input of the drive circuit, and a base coupled to that end of the first resistor which is situated nearest the drive circuit output. - View Dependent Claims (2, 3, 4, 5)
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6. A transistor circuit comprising:
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an input terminal for connection to a source of voltage, an output terminal for connection to a load, a first transistor connected in series between said input and output terminals for controlling current to a load, a drive circuit having an output coupled to a control electrode of the first transistor via a resistor thereby to control the drive of said first transistor, and a voltage limiting circuit controlled by the emitter-collector voltage of the first transistor for limiting said emitter-collector voltage to a given value by limiting the drive to the first transistor when said emitter-collector voltage drops below said given value, said voltage limiting circuit including said resistor and a second transistor of the same conductivity type as the first transistor with the second transistor connected between an output electrode of the first transistor and a control input of the drive circuit, and means coupling a control electrode of the second transistor to the resistor in a manner such that the second transistor is responsive to the emitter-collector voltage of the first transistor to signal the drive circuit to limit the drive to the first transistor when the emitter-collector voltage of the first transistor drops below said given value. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14)
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Specification