Low power, low noise band-gap circuit using second order curvature correction

A cellular telephone comprising:

• a voltage regulator capable of receiving a supply voltage from a battery of ,said cellular telephone and generating a regulated output voltage;
• analog-to-digital circuitry capable of converting analog signal in said cellular telephone to digital signals;
• and
• a band-gap reference circuit capable of supplying a band-gap reference voltage to said voltage regulator and said analog-to-digital circuitry, wherein said band-gap reference voltage is relatively constant across an operating temperature range, said band-gap reference circuit comprising:
• a first current source for generating a first reference current;
• a first circuit branch for receiving a portion of said first referenced current, said first circuit branch comprising a first resistor having a positive temperature coefficient connected in series with a base-emitter junction of a first PNP diode having a negative temperature coefficient, wherein an emitter current of said first PNP diode develops a first combined voltage across said series connection of said first resistor and said base-emitter junction of said first PNP diode;
• a comparison circuit for comparing said first combined voltage to a base-emitter voltage of a second PNP diode and, in response to said comparison, adjusting said band-gap reference voltage;
• and
• a correction current generating circuit capable of injecting a correction current into an emitter of said second PNP diode, wherein said injected correction current at least partially offsets a non-linear drop-off in said band-gap reference voltage caused by said second PNP diode as temperature increases.

A method of operating a band-gap reference circuit comprising the steps of:

• generating a first reference current;
• receiving a portion of the first reference current in a first circuit branch comprising a first resistor having a positive temperature coefficient connected in series with a base-emitter junction of a first PNP diode having a negative temperature coefficient, such that an emitter current of the first PNP diode develops a first combined voltage across the series connection of the first resistor and the base-emitter junction of the first PNP diode;
• comparing the first combined voltage to a base-emitter voltage of a second PNP diode;
• in response to the comparison, adjusting a band-gap reference voltage;
• and
• injecting a correction current into an emitter of the second PNP diode, wherein the injected correction current at least partially offsets a non-linear drop-off in the band-gap reference voltage caused by the second PNP diode as temperature increases.