A low noise operational amplifier design using subthreshold operation

Subthreshold MOSFETs biased at 5 /spl mu/A have been used to create scaleable, low noise, operational amplifiers. The operational amplifiers utilize input transistors operating in the subthreshold region and have been fabricated in two submicron CMOS processes. They demonstrate lower equivalent input noise voltage, more voltage headroom, and comparable or greater gain-bandwidth product than equivalent op amps operating strictly in saturation.