Patent ID: 7768343

Claim:
A start-up circuit for a current and/or voltage reference in which the reference comprises: a bandgap core including complementary PTAT (proportional-to-absolute-temperature) and CTAT (complementary-to-absolute-temperature) networks, wherein the PTAT and CTAT networks each include at least one diode; and an output circuit for outputting the reference, wherein the output circuit acts to combine outputs from the PTAT and CTAT networks; wherein the start-up circuit comprises: a sampling circuit to sample current in a diode of one of the PTAT and CTAT networks, the sampling circuit including an emulation diode structured in equivalence to that of the diode that is sampled, a differential amplifier, one differential input of the differential amplifier being connected to sample voltage at the diode that is sampled and the other differential input being connected to the emulation diode such that current through the emulation diode is substantially the same as current through the diode that is sampled, and such that voltage across the emulation diode is substantially the same as voltage across the diode that is sampled, and a transistor connected to the differential amplifier to create a negative feedback relationship for the differential amplifier; and a current injection circuit which injects current into the PTAT and CTAT networks if the current sampled by the sampling circuit is not higher than a pre-designated low value, wherein the injection of current is triggered at least partially based on a change of voltage across a resistor connected across the emulation diode to ensure that current flows through the transistor of the sampling circuit and thereby activates the negative feedback relationship of the differential amplifier.