High-precision PTAT current source based on the Meijer cell.

Proportional to absolute temperature (PTAT) current sources are one of the most important building blocks in analogue circuit design. An important PTAT current source is the Meijer all-NPN cross-quad circuit, where the PTAT output current does not present a strong dependence on the bias current and requires only four matched transistors to be realised, being adequate to be implemented with discrete circuits. In this paper, we present a technique that improves the performance of the Meijer cross-quad PTAT current source and minimises the deviations from the ideal behaviour by simply adding two transistors and adjusting the cell bias voltage. Simulated results in the -40 C to 85°C temperature range show that the errors were reduced by two orders of magnitude by using the novel technique, and a maximum non-linearity of 0.44 ppm/°C was obtained. A prototype of the circuit was built using the LM3046 transistor array, and a maximum deviation from the PTAT ideal current of only 0.06% was measured in 0–80°C, while in the conventional PTAT circuit an error of 0.81% was measured. [ABSTRACT FROM AUTHOR]