A very low offset voltage operational amplifier using field programmable floating-gate technology

A very low offset voltage operational amplifier that can be field programmable is described. Offset reduction is achieved by programming two floating gate transistors that form an important part of a single-stage folded cascode amplifier. A novel programming method that requires just four additional pins and an LMS algorithm was used. Floating-gate transistors were programmed for a minimum offset voltage of ±20µV using 1.2µm CMOS process. Programmed operational amplifiers can be used in continuous-time operation for a long period of time without the need of reprogramming. Experimental results show that this offset reduction scheme is a viable approach to low cost precision operational amplifier fabrication.