Voltage-controlled current source with variable supply current

Details Voltage-controlled current source with variable supply current Voltage-controlled current source with variable supply current

1999-11-01

2001-03-20

Riley, Shawn (Department: 2838)

Electricity: power supply or regulation systems

Self-regulating

Using a three or more terminal semiconductive device as the...

Reexamination Certificate

active

06204655

ABSTRACT:

The present invention relates generally to electrical circuits and, more particularly, to a voltage-controlled current source with a variable supply current.
BACKGROUND
In conventional electrical circuits, current sources are often essential to a circuit design. One especially useful form of a current source is a voltage-controlled current source, in which the output current is dependent upon an input differential voltage. Depending on the application, a current source may be required to support dramatically different loads. That is, the current source may be required to operate at a high current output level for one time period, then operate at a low current output level for another time period. Conventional voltage-controlled current sources that operate to source a wide range of current levels generally are designed to include a large standby current to support the large current output required during high output modes (cycles). In these applications, the large standby current must be maintained even if the output current is low. A high standby current may result in an inefficient use of power, and also may cause undesirable heating.
SUMMARY
In one aspect, the invention provides a method for providing electrical output current. The method includes providing a supply current, providing a first and second voltage input signal for controlling output current and generating an output current based on a differential voltage measured between the first and second input voltage signals including increasing the supply current as the output current increase.
In another aspect, the invention provides a device for providing electrical current and includes biasing circuitry providing a biasing current I
CC
and input circuitry including a first and second voltage input. The input circuitry is operable to receive the biasing current I
CC
and to divide the biasing current I
CC
based on the differential voltage measured between the first and second voltage inputs producing first and second biasing currents. A pair of translinear circuits is included that are operable to receive the first and second biasing currents and responsive thereto produce a first and second output current. The first and second output currents are summed to produce a final output current for the device where the final output current is a minimum of I
CC
when the differential voltage is approximately zero volts.
Aspects of the invention can include one or more of the following advantages. A current boost circuit is provided that can generate an output current that is based on the magnitude of a differential input voltage. The current boost circuit includes a supply current that increases as the output current increases. No standby high supply current is required when the output of the current boost circuit is low. The current boost circuit can be customized to increase or decrease gain characteristics of the device and limit current output for the device.
Other features and advantages of the invention will become apparent from the following description and from the claims.


REFERENCES:
patent: 4055774 (1977-10-01), Ahmed
patent: 5936393 (1999-08-01), Nauta
Gilbert,IEEE Journal of Solid-State Circuits, SC-3(3):353-365 Sep. 1968.
Gilbert,IEEE Journal of Solid-State Circuits, SC-3(3):365-373 Sep. 1968.

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