Patent ID: 7193454

Claim:
A PTAT voltage generating circuit comprising: a primary impedance element across which a PTAT voltage is developed, a first circuit for generating a first voltage level for applying to a first end of the primary impedance element, the first voltage level being provided as a function of the difference of N first base-emitter voltages and M second base-emitter voltages, N and M being integer values greater than zero and being of values different to each other, the first circuit comprising a first transistor stack having at least one first transistor for providing at least one of the N first base-emitter voltages, and a second transistor stack having at least one second transistor for providing at least one of the M second base-emitter voltages, each first transistor being operated at a first current density, and each second transistor being operated at a second current density, the second current density being different to the first current density, a first impedance element and a first op-amp configured to operate in a closed loop mode co-operating with the first and second transistor stacks so that a voltage difference of the first and second base-emitter voltages in the respective first and second transistor stacks is developed across the first impedance element for providing at least a part of the first voltage level, and a second circuit for generating a second voltage level for applying to a second end of the primary impedance element, the second voltage level being provided as a function of P of said N first base-emitter voltages, where P is an integer value greater than zero, the second circuit comprising a second op-amp configured to operate in a closed loop mode and co-operating with the first transistor stack for producing the P of said N first base-emitter voltages, the second circuit co-operating with the first circuit and with the primary impedance element so that the voltage developed across the primary impedance element by the difference of the first and second voltage levels comprises said PTAT voltage.