Wide Range, Process and Temperature Compensated Voltage Controlled Current Source

This paper presents a wide range, voltage controlled-current source circuit that is optimized to compensate for both process and temperature variations. Compensation for process variations is realized by cancellation of the threshold voltage variations. Temperature compensation is applied by the use of a poly resistor. Ninety samples from 3 different chips of the same wafer run were measured, and for the nominal value of 25 nA, current sources have a standard deviation of 1.22% (4.8 × improvement over an uncompensated current reference). The simulated standard deviation is 8%, resulting a simulated improvement factor of 8×, when samples from different wafer runs are to be measured. Measured temperature drift is 250 ppm/°C for a temperature range of 0-80°C. For the mentioned performance, the circuit consists of only 7 components occupying an area of 64 μm × 91 μm, using AMS 0.35 μm, 5 V CMOS process technology. The new current source is used to mimic the behavior of an infrared detector, which creates current in the range of 1-50 nA. A modified version of proposed current source is also designed with no off-chip bias voltages, and has a temperature coefficient of 57 ppm°C for 9 nA with an acceptable process compensation.