Curvature corrected bandgap reference circuit and method

A curvature corrected bandgap reference circuit, comprising:

• first and second bipolar transistors having their bases and collectors coupled to first and second circuit common points, respectively;
• first and second nodes;
• third and fourth field-effect transistors (FETs) having their gates connected to a third node and their drain-source circuits connected between a supply voltage and said first and second nodes, respectively, said third and fourth FETs arranged to provide first and second currents I1 and I2 to said first and second nodes, respectively, the emitter of said first bipolar transistor coupled to said first node;
• a differential amplifier connected to said first and second nodes at its inputs, the output of which is connected to said third node and arranged to control said third and fourth FETs such that the voltages at said first and second nodes are equal and said first and second currents are maintained in a fixed ratio;
• a first resistor connected between said second node and a third node;
• a second resistor connected between said third node and the emitter of said second bipolar transistor;
• a third resistor connected between said second node and said first circuit common point;
• said circuit arranged such that said first and second currents are substantially temperature invariant when the voltages at
• said first and second nodes are equal such that the signal across said second resistor includes a temperature proportional component and a residual component, wherein said residual component is of the form:
• (kT/q)ln((T0−Tx)/(T−Tx)),
• where T0 is a normalizing measurement temperature and Tx is the zero intercept of said temperature proportional component, said circuit arranged such that said residual component substantially compensates the base-emitter voltage curvature term present in the current in said third resistor.

A curvature corrected bandgap reference circuit, comprising:

• a first bipolar transistor operated such that it has a constant operating current and a base-emitter voltage Vbe1;
• and
• a second bipolar transistor operated such that it has an operating current consisting of an approximately temperature proportional component and a non-linear component and a base-emitter voltage Vbe2;
• such that the ratio of the current densities in said first and second bipolar transistors varies with temperature and the difference voltage ΔVbe=Vbe1−Vbe2 includes a residual component which approximately compensates bandgap curvature error.

A method of generating a correction voltage which compensates bandgap curvature error, comprising:

• operating a first bipolar transistor operated such that it has a constant operating current and a base-emitter voltage Vbe1;
• and
• operating a second bipolar transistor such that it has an operating current consisting of an approximately temperature proportional component and a non-linear component, and a base-emitter voltage Vbe2;
• such that the ratio of the current densities in said first and second bipolar transistors varies with temperature and the difference voltage ΔVbe=Vbe1−Vbe2 includes a component which approximately compensates bandgap curvature error.