Analog field programmable CMOS operational transresistance amplifier (OTRA)

This paper demonstrates a approach to design the field programmable CMOS operational transresistance amplifier. All the MOSFETs are replaced by the floating gate MOSFETs to make the OTRA design programmable. The charge at the floating gate can be programmed after fabrication, based on Hot-e-injection and Fowler-Nordheim tunneling techniques. This programming charge at floating gate results in threshold voltage variation in these MOSFETs, which in turn can modify circuit's specifications. The high frequency small signal analysis of the design is prepared and specifications of the design are re-derived in terms of threshold voltages of the MOSFETs. The expressions of output voltage, transresistance, input impedance, output impedance and offsets are derived in terms of threshold voltages of respective MOSFETs. In order to achieve circuits AC and DC characteristics, the circuit is simulated using BSIM3 level49 MOSFET models in T-spice 0.35um CMOS process. The simulated results shows 13 bit programming precision in transresistance, input impedance, output impedance, Temperature stability and dc offsets with respect to threshold voltage of respective MOSFETs.