A PTAT current is a current proportional to absolute temperature. PTAT current sources are used in electronic circuits for supplying at least one temperature-dependent current. They may also be used in temperature sensor electronic circuits or in circuits for controlling functions in association with a time base.
Generally, to generate a PTAT current reference in an electronic circuit integrated in a silicon substrate, a conventional resistor is used in a current generation branch. The precision of such a resistor may vary by ±30% with respect to an estimated value according to the manufacturing method, for example of MOS type. It is often necessary to calibrate such a resistor at the end of the manufacturing process to ensure that the PTAT current reference is sufficiently precise, which is a drawback.
To calibrate the PTAT current reference, it is possible to use a network of resistors and programmable switches connected to the resistors to generate the current. This requires, at the end of any manufacturing process, measuring the current value and controlling the connection of several resistors to obtain the desired PTAT current reference. This complicates operations for adapting the current reference, which constitutes a drawback.