CMOS bandgap voltage reference

A method of generating a bandgap voltage comprising the steps of:

• a) generating a first PTAT voltage across a first impedance and a second PTAT voltage across a first device in a first current path;
• b) generating a third PTAT voltage across a second device in a second current path, each of the first and second devices generating the second and third PTAT voltages operates in accordance with a diode junction equation for the corresponding device;
• c) regulating, with a feedback voltage signal of a feedback amplifier, the current in the first and second current paths such that a sum of the first and second PTAT voltages is substantially equivalent to the third PTAT voltage, the sum of the first and second PTAT voltages provided to a first input terminal of the feedback amplifier and the third PTAT voltage provided to a second input terminal of the feedback amplifier;
• d) generating, with a voltage buffer, the bandgap voltage from 1) a voltage across a second impedance in a feedback path from the output of the voltage buffer to a first input terminal of the voltage buffer and 2) the third PTAT voltage at a second input terminal of the voltage buffer, the voltage across and current through the second impedance being substantially proportional to the first PTAT voltage across and current through the first impedance, respectively;
• and
• e) regulating the voltage across the second impedance with the current through the feedback path based on the third PTAT voltage so as to regulate the bandgap voltage.

A bandgap voltage reference circuit comprising:

• PTAT voltage generating means for 1) generating a first PTAT voltage across a first impedance and a second PTAT voltage across a first device in a first current path, and 2) generating a third PTAT voltage across a second device in a second current path, each of the devices generating the second and third PTAT voltages operates in accordances with a diode junction equation for the corresponding device;
• voltage biasing means for regulating, with a feedback voltage signal of a feedback amplifier, the current in the first and second current paths such that a sum of the first and second PTAT voltages is substantially equivalent to the third PTAT voltage, a sum of the first and second PTAT voltages provide to a first input terminal of the feedback amplifier and the third PTAT voltage provided to a second input terminal of the feedback amplifier;
• bandgap voltage generating means for 1) generating, with a voltage buffer, the bandgap voltage from 1) a voltage across a second impedance in a feedback path from the output of the voltage to a first input terminal of the voltage buffer and 2) the third PTAT voltage at a second input terminal of the voltage buffer, the voltage across and current through the second impedance being substantially proportional to the first PTAT voltage across and current through the first impedance, respectively;
• and
• means for regulating the voltage across the second impedance with the current through the feedback path based on the third PTAT voltage so as to regulate the bandgap voltage.

An integrated circuit having a bandgap voltage reference circuit (e.g., 100 in FIG. 1) comprising:

• a proportional to absolute temperature (PTAT) voltage generator (e.g., 190) adapted to generate:
• in a first current path, a first PTAT voltage across a first impedance (e.g., 110) and a second PTAT voltage across a first device (e.g., 106);
• and
• in a second current path, a third PTAT voltage across a second device (e.g., 108), wherein:
• each of the first and second devices generating the second and third PTAT voltages operates in accordance with a diode junction equation for the corresponding device;
• the first device is coupled in series with the first impedance in the first current path;
• and
• the PTAT voltage generator includes a feedback amplifier coupled to receive the sum of the first and second PTAT voltages at its first input terminal and the third PTAT voltage at its second input terminal, the feedback voltage signal at the output terminal of the feedback amplifier employed to regulate the current in the first and second current paths such that a sum of the first and second PTAT voltages is substantially equivalent to the third PTAT voltage;
• and
• a voltage buffer (e.g., 192) adapted to receive a voltage across a second impedance (e.g., 124) and the third PTAT voltage to generate a bandgap voltage at an output terminal (e.g., N4), wherein:
• the voltage buffer comprises:
• a second current mirror (e.g., 114, 170) providing a third current in a third current path proportional to the first current;
• an operational amplifier (e.g., 116) adapted to receive at one input terminal the voltage across the second impedance and at the other terminal the third PTAT voltage and to provide the bandgap voltage, and wherein:
• 1) a portion of the current in the third path flows through the second impedance to provide the voltage across the second impedance in proportion to the first PTAT voltage, 2) the voltage across and current through the second impedance are substantially proportional to the first PTAT voltage across and current through the first impedance, respectively;
• and 3) the voltage buffer biases the voltage across the second impedance with the third PTAT voltage so as to regulate the bandgap voltage.