Low-voltage bandgap voltage reference circuit

1. A bandgap reference voltage generating circuit, comprising:

a proportional to absolute temperature (PTAT) voltage generating means generating a PTAT voltage;

a complementary to absolute temperature (CTAT) voltage generating means generating a CTAT voltage;

a temperature coefficient determining means interconnecting said PTAT voltage generating means and said CTAT voltage generating means;

wherein said CTAT voltage generating means comprises:

an op-amp configured for being powered by a supply voltage, said op-amp having inverting and noninverting op-amp inputs and an op-amp output;

a first CTAT voltage generating means generating a first CTAT voltage at said inverting op-amp input; and

a second CTAT voltage generating means generating a second CTAT voltage at said noninverting op-amp input, said first and second CTAT voltages resulting from currents of a predetermined ratio in said first and second CTAT voltage generating means; and

wherein said temperature coefficient determining means comprises:

a first resistor electrically interconnecting said first CTAT voltage generating means and an intermediate node;

a second resistor electrically interconnecting said second CTAT voltage generating means and said intermediate node; and

a third resistor interconnecting said intermediate node and said PTAT voltage source.

2. A bandgap reference voltage generating circuit, comprising:

an op-amp configured for being powered by a supply voltage, said op-amp having inverting and noninverting op-amp inputs and an op-amp output;

a first device having at least one p-n junction electrically connected between said inverting input and ground potential;

a first resistor and a second device having at least one second p-n junction electrically connected between said noninverting input and ground potential, said at least one second p-n junction of said second device having a cumulative current density flowing therethrough that is a predetermined ratio smaller than a cumulative current density flowing through said at least one first p-n junction;

a PTAT voltage generating means including a current mirroring device electrically connected to said op-amp output and mirroring a PTAT current received therefrom, a second resistor electrically connected to said current mirroring device, said PTAT current flowing through said second resistor and developing a PTAT voltage;

a first temperature-coefficient (TC) determining resistor electrically interconnecting said inverting input of said op-amp to a node intermediate said current mirroring device and said second resistor connected thereto; and

a second TC determining resistor electrically interconnecting said noninverting input of said op-amp to said node.

3. A bandgap reference voltage generating circuit, comprising:

a first and second MOSFET configured as a differential amplifier having first and second inputs;

a first device having at least one p-n junction electrically connected between said first input of said differential amplifier and ground potential;

a first resistor and a second device having at least one p-n junction electrically connected between said second input of said differential amplifier and ground potential, said at least one second p-n junction of said second device having a cumulative current density flowing there through that is a predetermined ratio smaller than a cumulative current density flowing through said at least one first p-n junction;

a PTAT voltage generating means electrically interconnected with a drain of said first MOSFET of said differential pair, said PTAT voltage generating means including a current mirroring device mirroring a PTAT current flowing through said second device, a second resistor electrically connected to said current mirroring device, said PTAT current flowing through said second resistor and developing a PTAT voltage;

a first temperature-coefficient (TC) determining resistor electrically interconnecting said second input of said differential amplifier to a node intermediate said current mirroring device and said second resistor connected thereto; and

a second TC determining resistor electrically interconnecting said second input of said differential amplifier to said node.

4. The bandgap reference voltage generating circuit of claim 3 , further comprising a current feedback loop including third, fourth and fifth current feedback MOSFETS substantially reducing any voltage offset across the inputs the differential amplifier at equilibrium.

5. The bandgap reference voltage generating circuit of claim 3 , further comprising a start-up circuit, said start-up circuit including:

first, second and fourth start-up MOSFETs configured for being electrically interconnected between a supply voltage and ground potential, said first start-up MOSFET configured for having its drain electrically connected to said supply voltage, its gate electrically connected to the drain of said first MOSFET of said differential amplifier, and its source electrically connected to a drain of said second start-up MOSFET, a gate of said second start-up MOSFET electrically connected to said gate of said first MOSFET of said differential amplifier, and a source of said second start-up MOSFET electrically connected to a drain of said fourth start-up MOSFET, a gate of said fourth start-up MOSFET being electrically connected to said current feedback loop, a source of said fourth start-up MOSFET being electrically connected to ground potential; and

a third start-up MOSFET having its gate electrically connected to the drain of said fourth start-up MOSFET and the source of said second start-up MOSFET, its source electrically connected to ground potential, and its drain electrically connected to the drain of said first MOSFET of said differential amplifier.