Sub-bandgap reference using a switched capacitor averaging circuit

Abstract

A sub-bandgap reference circuit yielding a reference voltage smaller than the bandgap voltage of silicon. The circuit generates a negative temperature coefficient signal V.sub.be and an oppositely tracking (positive temperature coefficient) .DELTA.V.sub.be, and takes the average of two signals related to .DELTA.V.sub.be -V.sub.be to yield a temperature-compensated voltage of one-half the bandgap voltage of silicon. The circuit features an unequal area current mirror feeding the diodes and resistors used to generate the .DELTA.V.sub.be -V.sub.be signals using low supply voltages (less than 1.5 volts). A standard CMOS implementation provides low power consumption at a supply voltage of only 1 volt with a good temperature coefficient. The averaging circuit may be implemented by a continuous time divider or by using switched capacitor techniques. The loop amplifier used in the .DELTA.V.sub.be -V.sub.be circuitry operates with low headroom in part due to a n-well biasing scheme that lowers the effective threshold voltage of the p-channel FETs used in the loop amplifier.

Dependencies are inferred from the claim text.