CMOS voltage controlled current source

Claim 1

A voltage controlled current source for generating an output current which is linearly proportional to an input voltage comprising: a. differential amplifier means having a first input coupled to said input voltage and having a second input, for generating an output signal indicative of the difference in voltage between said first input and said second input; b. high gain stage means responsive to the output of said differential amplifier means for amplifying said output signal and for generating a reference voltage; c. output means responsive to said output signal for generating said output current which is linearly proportional to said reference voltage; and d. feedback means coupling said reference voltage to said second input for causing said reference voltage to equal said input voltage wherein said high gain stage comprises: e. a first MOSFET device of a first conductivity type having a source coupled to a first power supply conductor, a gate coupled to said output signal and a drain; f. a second MOSFET device of a second conductivity type opposite to the first conductivity type having a source connected to a second power supply conductor, a gate coupled to the drain of said first MOSFET device and a drain coupled to the drain of said first MOSFET device; g. a third MOSFET device of the second conductivity type having a source coupled to the second power supply conductor, a gate coupled to the gate of the second MOSFET and a drain; h. impedance means coupled between the drain of the third MOSFET and the first power supply conductor for generating said reference voltage.