Patent Number: 6,344,769

Title: Precision differential switched current source

Abstract: A switched current source is provided for differentially switching highcurrents onto different loads at high speed and with a high degree ofaccuracy. The switched current source includes a differential amplifier,which receives an input current and selectively provides first and secondoutput currents, a voltage amplifier, and a capacitor, which compensatesthe frequency response of certain feedback amplifiers and stores thepotential of a certain node during transients. The differential amplifierincludes two transistors each connected to the input current and forproviding one of the output currents when activated. The first and secondtransistors are controlled by first through fourth switches. The firstswitch and the second switches turn on the first and second transistors,respectively, when closed. The third and the fourth switches pull down thefirst and second transistors, respectively, when closed. By pulling downthe first and second transistors, the circuit increases operation speedand accuracy by preventing them from floating. The first and thirdswitches are always in opposite positions, as are the second and fourthswitches, i.e., when the first switch is open, the third switch is closedand vice versa. The current input may come from a current mirror connectedto the common source of the first and second transistors.

Inventors: Giuroiu; Horia (Campbell, CA)


International Classification: G05F 3/08 (20060101); G05F 3/26 (20060101); G05F 001/10 ()

Expiration Date: 02/05/2014