Rail-to-rail differential input amplification stage with main and surrogate differential pairs
AssigneeUT-Battelle, LLC
InventorsCharles Britton, Stephen Smith
Life of this patent
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Abstract
An operational amplifier input stage provides a symmetrical rail-to-rail input common-mode voltage without turning off either pair of complementary differential input transistors. Secondary, or surrogate, transistor pairs assume the function of the complementary differential transistors. The circuit also maintains essentially constant transconductance, constant slew rate, and constant signal-path supply current as it provides rail-to-rail operation.
Claims42
An essentially constant transconductance, constant slew rate, noncomplementary rail-to-rail differential input amplification stage having a common-mode input voltage range including low, mid, and high range, comprising:
- a main input differential pair of transistors receiving input signal voltages from an external source;
- a surrogate input differential pair of transistors biased with a voltage offset from said main input differential pair of transistors;
- means for controllably isolating said surrogate input differential pair of transistors from the main signal path;
- means for sensing the amount of bias current in said main input differential pair of transistors;
- and
- means for providing a controlled amount of bias current to said surrogate input differential pair of transistors.
An essentially constant transconductance, constant slew rate, constant signal-path supply-current, fully complementary rail-to-rail differential input amplification stage having a common-mode input voltage range including low, mid and high range, comprising:
- two sets of opposite-polarity input differential pairs of transistors receiving input signal voltages from an external source;
- two sets of surrogate input differential pairs of transistors biased with voltage offsets from said main input differential pairs of transistors;
- means for controllably isolating said surrogate input differential pairs of transistors from the main signal paths;
- means for sensing the amounts of bias currents in said main input differential pairs of transistors;
- and
- means for providing controlled amounts of bias currents to said surrogate input differential pairs of transistors.
Dependencies are inferred from the claim text.