Precision voltage reference for systems such as analog to digital converters

Claim 1

A circuit for developing first and second reference sources for analog to digital converters or other electrical systems, comprising: a transistor means having a control electrode and a pair of output electrodes, the transistor means having a negative temperature coefficient; a reference diode means having a positive temperature coefficient and connected in series with one of said output electrodes of said transistor means, the temperature coefficients of said transistor means and said reference diode means being equal in magnitude at a predetermined magnitude of current flowing therethrough; first and second operational amplifiers each having inverting input, non-inverting input and output terminals, the output terminal of said first operational amplifier establishing a first reference source; a first signal path established between the inverting input terminal of said second operational amplifier and said first reference source; a second signal path established between said first reference source and a junction between said transistor means and said reference diode means; the non-inverting input terminal of said second operational amplifier being connected to the ground; the output terminal of said second operational amplifier establishing a second reference source; a first resistor connected between said second reference source and the other of said output electrodes of said transistor means and having a resistance value sufficient to establish the predetermined current magnitude; the inverting and non-inverting input terminals of said first operational amplifier being connected respectively, to a junction between said first resistor and said transistor means and to the ground; and a precision resistance divider means connected between said first reference source and the ground; an output of said divider means being applied to the control electrode of said transistor means.