Biasing CMOS amplifiers using MOS transistors in subthreshold region

The implementation of large-valued floating resistive elements using MOS transistors in subthreshold region is addressed. The application of these elements to bias wideband AC coupled amplifiers is discussed. Simple schemes to generate the gate control voltages for the MOS transistors implementing large resistors so that they remain in high resistive state with large signal variations are discussed. Experimental results of a test chip prototype in 0.5-μm CMOS technology are presented that verify the proposed technique.