Current source circuit

A current source circuit comprising a first current source means producing a constant value of current, a second current source means for producing a controlled amount of current, a current inverting circuit having a first current terminal coupled to a current output terminal of said first current source means and a second current terminal coupled to a current output terminal of said second current source means, said current inverting circuit producing at said first current terminal substantially the same amount of current as the amount of current produced by said second current source to thereby derive the difference in current between said constant value of current and the controlled amount of current from an intermediate junction of said first current terminal and the current output terminal of said first current source means, and controlling means responsive to said difference for controlling said second current source means so as to make the amount of said controlled current substantially equal to said constant value.

A current source circuit comprising a current inverting circuit having a first current terminal and a second current terminal, a first current source arranged between said first current terminal and a first potential, said first current source producing a constant value of current, an amplifier, second current source arranged between said second current terminal and said first potential, said second current source producing a controlled amount of current in response to an output of said amplifier, a series circuit arranged between said first current course and said second current source, said series circuit including a capacitor and switching means, an intermediate junction of said capacitor and switching means coupled to an input of said amplifier.

A current source circuit comprising a first field effect transistor having a source supplied with a first potential, a second field effect transistor having a source supplied with said first potential and a gate coupled to the gate of said first field effect transistor and the drain of said second field effect transistor, a first current source means arranged between the drain of said first field effect transistor and a second potential, said first current source means producing a constant value of current, a third field effect transistor having a source coupled to the drain of said second field effect transistor, resistor means arranged between the drain of said third field effect transistor and said second potential, a differential amplifier having an output coupled to the gate of said third field effect transistor and having first and second input terminals, switching means arranged between said first input terminal and the drain of said first field effect transistor, capacitor means arranged between said first input terminal and the drain of said third field effect transistor and means for supplying said second input terminal with a predetermined potential.

A circuit comprising a current inverting circuit having a first current terminal and a second current terminal, a first current source producing a constant value of current, a current circuit responsive to an input voltage for producing corresponding value of current, an output of said current circuit being coupled to said first current terminal, a capacitor having a terminal coupled to an input of said current circuit, first switch means for operatively coupling said second current terminal and an ouptput of said current source, second switch means for operatively coupling said terminal of said capacitor and said second current terminal, an analog to digital converter, and third switch means for coupling said second current terminal with an input of said analog to digital converter when said second switch is in non-conductive state.

An analog to digital converter circuit comprising first means for converting an input voltage to corresponding value of current, current source means for producing a constant value of current, detection means for detecting the difference in value between said corresponding value and said constant value, capacitor means coupled to an input of said first means, feedback means for operatively coupling said capacitor with an output of said detection means to thereby make said corresponding value substantially equal to said constant value, and second means for converting a value of an input current into a digital value, wherein said corresponding value of current after operation of said feedback means is used as a reference current for said second means.