CMOS sub-bandgap reference with an operating supply voltage less than the bandgap
AssigneeNational Semiconductor Corporation
InventorsJames T. Doyle, Yushan Li
Life of this patent
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Abstract
A circuit that outputs a stable reference voltage with an operating supply voltage less than the band gap potential and also less than a zero-bias threshold voltage. In one embodiment, the sub-band gap circuit includes an operational amplifier having an N-well input stage operating in the sub-threshold region, and a proportional to absolute temperature (PTA) current source having a forward-biased P-bulk. In another embodiment, the operational amplifier realizes sub-one volt operation by making use of back gating as the input stage, allowing full rail-to-rail input and output swings.
Claims20
A sub-bandgap circuit comprising:
- an operational amplifier having an N-well input stage;
- and
- a proportional to absolute temperature current source coupled to said operational amplifier and having a forward-biased P-bulk, wherein said circuit outputs a reference voltage that is less than the bandgap potential of silicon with an operating supply voltage less than the bandgap potential of silicon.
A sub-bandgap circuit comprising:
- a zero current power-on reset;
- a pre-regulator coupled to said power-on reset;
- a proportional to absolute temperature current source coupled to said power-on reset, wherein a P-bulk of said current source is forward-biased;
- a resistor divider coupled to said P-bulk;
- and
- an operational amplifier coupled to said power-on reset, wherein said sub-bandgap circuit provides a reference voltage that is less than the bandgap potential of silicon with an operating supply voltage less than the bandgap potential of silicon and less than a zero-bias threshold voltage.
A sub-bandgap circuit comprising:
- a zero current power-on reset;
- a pre-regulator coupled to said power-on reset;
- a Vittoz current source coupled to said power-on reset;
- a resistor divider coupled to said current source;
- and
- an operational amplifier coupled to said power-on reset, said operational amplifier having an N-well input stage, wherein said sub-bandgap circuit provides a reference voltage that is less than the bandgap potential of silicon with an operating supply voltage less than the bandgap potential of silicon and less than a zero-bias threshold voltage.
Dependencies are inferred from the claim text.