Abstract: A primary differential input pair of transistors and a secondary differential input pair of transistors are capable of operating in parallel to provide load current. A level-shifting pre-stage to the secondary differential pair downwardly level-shifts rail-to-rail input signals. Doing so prevents the secondary differential pair from entering cut-off. A tail current shunt device provides tail current to the secondary differential pair as the primary differential pair approaches cut-off when a common-mode component of the input signals approaches the positive voltage rail. Consequently, the sum of currents through first differential input transistors associated with the primary and secondary differential input pairs remains constant to the first load. Likewise, the sum of currents through the second differential input transistors associated with the primary and secondary differential input pairs remains constant to the second load.

Abstract: A primary differential input pair of transistors and a secondary differential input pair of transistors are capable of operating in parallel to provide load current. A level-shifting pre-stage to the secondary differential pair downwardly level-shifts rail-to-rail input signals. Doing so prevents the secondary differential pair from entering cut-off. A tail current shunt device provides tail current to the secondary differential pair as the primary differential pair approaches cut-off when a common-mode component of the input signals approaches the positive voltage rail. Consequently, the sum of currents through first differential input transistors associated with the primary and secondary differential input pairs remains constant to the first load. Likewise, the sum of currents through the second differential input transistors associated with the primary and secondary differential input pairs remains constant to the second load.