Temperature compensation bandgap voltage reference and method

A bandgap voltage reference circuit with output curvature correction, comprising:

• (1) an uncorrected bandgap voltage reference cell that includes
• (a) first and second bipolar transistors having their bases connected together to provide a base output voltage, their collectors connected to receive respective collector currents, the emitter of the first cell transistor connected to a voltage reference through first and second series connected cell resistors, and the emitter of the second cell transistor connected to said voltage reference through the second but not the first cell resistor, said cell transistor being scaled in area to maintain a proportional to absolute temperature (PTAT) collector current for said second cell transistor, and
• (b) an output circuit connected to provide a final output voltage from said base output voltage that varies continuously with temperature over a predetermined temperature range,
• (2) an output voltage correction circuit comprising:
• (a) a correction bipolar transistor having its base connected to the bases of said first and second cell transistors, its emitter connected through a first correction resistor to the junction of said first and second cell resistors, and its collector connected to receive a current through a second correction resistor, and
• (b) an operational amplifier having inverting and non-inverting inputs and an output connected respectively to the collector, base and emitter of said correction transistor, said amplifier establishing a substantially constant collector current for said correction transistor through said second correction resistor, said substantially constant current controlling the base-emitter voltage of said correction transistor to establish a correction current through said first correction and second cell resistors that modifies said base output voltage continuously over said predetermined temperature range to compensate for said final output voltage variation in accordance with k.sub.1 T - k.sub.2 Tln(k.sub.3 T), where k.sub.1, k.sub.2 and k.sub.3 are constants and T is absolute temperature, the values of said resistors being selected to maintain a substantially constant base output voltage over said predetermined temperature range.

A bandgap voltage reference circuit with output temperature curvature correction, comprising:

• an uncorrected bandgap voltage reference cell that generates a voltage across a tail resistor, said voltage having a continuous temperature curvature component over a predetermined temperature range in the form k.sub.1 T - k.sub.2 Tln(k.sub.3 T), and that produces a base output voltage based upon said resistor voltage, where k.sub.1, k.sub.2 and k.sub.3 are constants and T is absolute temperature, and
• an output voltage correction circuit that comprises:
• a correction bipolar transistor having its base connected to said base output voltage, its emitter connected through a second correction resistor to provide a correction current to said tail resistor, and its collector connected to receive a current through a second correction resistor, and
• an operational amplifier having inverting and non-inverting inputs and an output connected respectively to the collector, base and emitter of said correction transistor, said amplifier producing a substantially constant current through said second correction resistor that establishes a correction current through said tail resistor, the resistance values of said resistors being selected so that said correction current produces a correction voltage across said tail resistor that various continuously with temperature over said predetermined temperature range and has the form -k.sub.1 T + k.sub.2 Tln(k.sub.3 T), thereby substantially cancelling the temperature curvature component of said uncorrected tail resistor voltage over said predetermined temperature range.

A method of compensating for continuous temperature-induced variations in the output voltage from a bandgap voltage reference cell over a predetermined temperature range, said cell including a bipolar cell transistor with a proportional to absolute temperature (PTAT) collector current, comprising:

• generating a collector current in a bipolar correction transistor that is substantially insensitive to temperature changes over said predetermined temperature range,
• obtaining the difference between the base-emitter voltage of said cell and correction transistors as a continuously varying function of temperature over said predetermined temperature range having the form k.sub.1 T - k.sub.2 Tln(k.sub.3 T), where k.sub.1, k.sub.2 and k.sub.3 are constants and T is absolute temperature,
• combining said difference with said base output voltage, and
• selecting the values of k.sub.1, k.sub.2 and k.sub.3 so that said base-emitter voltage difference substantially cancels said temperature-induced output voltage variations over said predetermined temperature range.