Current Reference Circuit Operable at Low Voltages Using Composite MOS Triode Resistor

Invasive biomedical applications involving acquisition and recording of biological signals require current reference generation circuits for low voltage front-end amplifier and filter circuits. However, achieving current reference using Self-Biased Current Source (SBCS) for these circuits at same low supply voltages poses requirement of resistors. In this work, we compare the effect of passive poly resistor and Composite Triode MOS Resistor (CTMR) on the performance of low voltage SBCS circuit using 0.18 µm standard SCL foundry process parameters and models of MOS, capacitor and resistor. For current reference generation of 371 nA, the temperature coefficient (ppm/degree Celsius) values for passive poly resistor and CTMR are 2400 and 2251 respectively. The Figure of Merit, FOM (ppm/degree Celsius) and Coefficient of variance (CV) at different process corners with Monte-carlo simulation (MCS) runs of 100 for CTMR are 0.93 and 0.16 times lower than that of passive poly resistor. The CTMR based SBCS is anticipated to be used in low voltage front-end biomedical applications.