×

Differential amplifier having rail-to-rail input capability and square-root current control

  • US 5,371,474 A
  • Filed: 02/17/1994
  • Issued: 12/06/1994
  • Est. Priority Date: 05/08/1992
  • Status: Expired due to Fees
First Claim
Patent Images

1. An electronic circuit operable between first and second supply voltages which constitute a power supply range including a first end range extending to the first supply voltage, a second end range extending to the second supply voltage, and an intermediate range extending between the end ranges, the circuit comprising:

  • first differential means for amplifying a differential input signal by largely dividing a first tail current into a pair of first main currents whose difference is representative of the input signal when its common-mode voltage VCM is in the intermediate and first ranges;

    second differential means for amplifying the input signal by largely dividing a second tail current into a pair of second main currents whose difference is representative of the input signal when VCM is in the intermediate and second ranges; and

    square-root means comprising a pair of primary control FETs having respective gate-to-source voltage whose sum is held largely constant during normal circuit operation, for controlling the tail currents so that the sum of their square roots is largely constant during circuit operation as VCM traverses the entire intermediate range and the end ranges.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×