Curvature-corrected band-gap voltage reference circuit

A band-gap voltage reference circuit comprising:

• a first and second transistor each having a base, collector and emitter electrodes, wherein said base electrodes of said first and second transistors are connected together;
• an amplifier device having its inverting input coupled to the emitter of a first transistor and its noninverting input coupled to the emitter of a second transistor to produce an output responsive to the difference between the currents through said first and second transistors;
• a differential current density device for producing different current densities in said first and second transistors, wherein a ratio of the current densities is temperature dependent;
• and
• an output terminal of said amplifier device, wherein said output terminal develops a substantially temperature independent voltage.

A method of compensating for second order temperature coefficients of band-gap output voltage reference circuits comprising the steps of:

• providing a pair of transistors, wherein each transistor has base, collector and emitter electrodes, wherein the transistors include a first transistor and a second transistor;
• providing an amplifier device having its noninverting input coupled to one transistor and further having its inverting input coupled to a second transistor, thereby producing an output responsive to the difference between the currents through said pair of transistors;
• producing different current densities in said pair of transistors, wherein a ratio of the current densities is temperature dependent;
• providing an output circuit for said amplifier device, wherein said output circuit includes an output terminal for developing an output voltage;
• providing a first resistor network comprising two resistors connected in series to the collector of said first transistor;
• providing a first resistor in said first resistor network that has a high temperature coefficient so that the output voltage of the band-gap circuit is temperature compensated to at least a second order.