A 3 - 14V rail-to-rail constant gm opamp in conventional 0.18µm CMOS process

A 3-14 V rail-to-rail constant g_m opamp for interfacing high voltage input signals was fabricated in a conventional 0.18 mum CMOS process and designed using standard 3.3 V I/O devices. High-voltage analog sub-circuits, including current sources, differential stages and common-source amplifiers for realizing the opamp were proposed. The test results showed that the variations on the g_m of the input stage for different supply voltages were less than 12.5%. The opamp has a unity bandwidth of 1.3 MHz and a current consumption of 40.7 muA at a supply voltage of 14 V.