Operational amplifier with positive and negative feedback paths for supplying constant current to a bandgap voltage reference circuit

Claim 2

A voltage regulator comprising: an operational amplifier having supply voltage terminals connected across a source of unregulated supply voltage, inverting and noninverting input terminals, and an output terminal; an essentially zero temperature coefficient, bandgap voltage reference circuit; circuit means connecting said voltage reference circuit in a negative feedback path for said amplifier between said output and said inverting input terminals such that said amplifier functions as a constant current source for said voltage reference circuit and said amplifier and voltage reference circuit combine to supply a regulated voltage at said output terminal; and a positive feedback network for said amplifier between said output and noninverting input terminals for establishing the value of said regulated voltage.

Claim 3

A voltage regulating circuit comprising: an operational amplifier having an inverting input terminal, a noninverting input terminal, an output terminal, and a pair of supply voltage receiving terminals; means for connecting said supply voltage receiving terminals to a source of unregulated supply voltage; a two terminal, essentially zero temperature coefficient, bandgap voltage reference circuit; means for connecting said voltage reference circuit in a negative feedback path between said output terminal and said inverting input terminal; a voltage divider network having first and second resistive sections; means for connecting said network between said output terminal and one of said supply voltage receiving terminals for establishing a voltage thereacross; means connecting a junction of said resistive sections to said noninverting input terminal for establishing a positive feedback path between said output terminal and said noninverting input terminal, the relative resistance values of said resistive sections establishing a regulated output voltage level at said output terminal; and resistance means connected between said one supply voltage terminal and a junction of said voltage reference circuit and said inverting input terminal for establishing a constant current flow in said negative feedback path through said voltage reference circuit.

Claim 4

A voltage regulating circuit comprising: an operational amplifier having an inverting input terminal, a noninverting input terminal, an output terminal, and a pair of supply voltage receiving terminals; means for connecting said supply voltage receiving terminals to a source of unregulated supply voltage; a two terminal, essentially zero temperature coefficient, bandgap voltage reference circuit; means for connecting said voltage reference circuit in a negative feedback path between said output terminal and said inverting input terminal; a voltage divider network having first and second resistive sections; means for connecting said network between said output terminal and one of said supply voltage receiving terminals for establishing a voltage thereacross; means connecting a junction of said resistive sections to said noninverting input terminal for establishing a positive feedback path between said output terminal and said noninverting input terminal, the relative resistance values of said resistive sections establishing a regulated output voltage level at said output terminal; and resistance means connected between said one supply voltage terminal and a junction of said voltage reference circuit and said inverting input terminal for establishing a constant current flow in said negative feedback path through said voltage reference circuit.