Switchable current source circuitry having a current mirror and a switching transistor coupled in parallel
AssigneeRaytheon Company
InventorCharles L. Vinn
Life of this patent
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Abstract
A switchable current source circuit having a current mirror and a switch, such switch including a current source coupled to the current mirror, such switch enabling or disabling current from the current source to pass to the input of the current mirror selectively in accordance with a control signal fed to such switch. In one embodiment, the switch includes a differential amplifier and the current source is part of the differential amplifier. One of a plurality of control signals is fed to control the differential amplifier with the differential amplifier serving as both a logic circuit and current source, therefore, reducing the number of circuit comparators required to provide a switchable current source circuit.
Claims10
A switchable current source circuit comprising:
- a current mirror;
- and,
- switch means, including a current source, coupled to the current mirror for enabling, or disabling, current from the current source to pass to an input of the current mirror selectively in accordance with a control signal fed to such switch means, such switch means including a transistor having the emitter and collector thereof coupled in parallel with the current mirror, the base of the transistor being fed by the control signal, and wherein in response to one level of the control signal, such switch means places the transistor in a non-conducting condition between the collector and emitter to enable the current from the current source to pass to the input of the current mirror, such current mirror producing an output current through a load coupled thereto with a level proportional to the current produced by the current source, while in response to a second level of the control signal, such switch means places the transistor in a conducting condition between the emitter and collector and current from the current source passes through the emitter and collector of the transistor to prevent such current from the current source from passing to the input of the current mirror, such current mirror thereby being prevented from producing the output current through the load.
A switchable current source circuit, comprising:
- (a) a circuit means having:
- (i) a first transistor;
- and
- (ii) a diode coupled between a base and emitter of the first transistor;
- (b) a second transistor having:
- a collector coupled to the base of the first transistor;
- an emitter coupled to the emitter of the first transistor;
- and a base adapted for coupling to a first logic signal source;
- (c) a differential amplifier comprising:
- (i) a current source;
- (ii) a third transistor;
- (iii) a second diode coupled between a base and emitter of the third transistor, the emitter of the third transistor being coupled to the emitter of the first and second transistors;
- and,
- (iv) a pair of transistors, an emitter of each one thereof being coupled in common to the current source;
- a first one of such pair of transistors having:
- a base adapted for coupling to a second control signal;
- and, a collector electrode coupled to:
- the base of the first transistor;
- the collector of the second transistor;
- and, a collector of the third transistor;
- and wherein the second one of the pair of transistors has a collector coupled to the base of the third transistor.
Dependencies are inferred from the claim text.