A rail-to-rail amplifier input stage with +/- 0.35%gm fluctuation Academic Article uri icon


  • A new scheme for achieving rail-to-rail input to an amplifier is introduced. Constant gm is obtained by using tunable level shifters and a single differential pair. Feedback circuitry controls the level shifters in a manner that fixes the common-mode input of the differential pair, resulting in consistent and stable operation for rail-to-rail inputs. As the new technique avoids using complimentary input differential pairs, this method overcomes problems such as common-mode rejection ratio and gain-bandwidth product degradation that exist in many other designs. The circuit was fabricated in 0.5-μm process. The resulting differential pair had a constant transconductance that varied by only ±0.35% for rail-to-rail input common-mode levels. The input common-mode range extended well past the supply levels of ± 1.5 V, resulting in only ± 1% fluctuation in gm for input common modes from -2 to 2 V. © 2005 IEEE.

published proceedings


author list (cited authors)

  • Fischer, T. W., Karsilayan, A. I., & Sanchez-Sinencio, E.

citation count

  • 27

complete list of authors

  • Fischer, TW||Karsilayan, AI||Sanchez-Sinencio, E

publication date

  • February 2005