A novel low-voltage high precision current reference based on subthreshold MOSFETs

A novel topology low-voltage high precision current reference based on subthreshold Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) is presented. The circuit achieves a temperature-independent reference current by a proper combination current of two first-order temperature-compensation current references, which exploit the temperature characteristics of integrated poly2 resistors and the I–V transconductance characteristics of MOSFET operating in the subthreshold region. The circuit, designed with the 1st silicon 0.35 μm standard CMOS logic process technology, exhibits a stable current of about 2.25 μA with much low temperature coefficient of 3×10−4 μA/°C in the temperature range of −40∼150 °C at 1 V supply voltage, and also achieves a better power supply rejection ratio (PSRR) over a broad frequency. The PSRR is about −78 dB at DC and remains −42 dB at the frequency higher than 10 MHz. The maximal process error is about 6.7% based on the Monte Carlo simulation. So it has good process compatibility.