Differential amplifier circuit with rail-to-rail capability

摘要

@ A differential amplifier circuit contains a pair of complementary input portions (3, 5 and 4, 6). The input portions amplify a common differential input signal to produce corresponding amplified differential signals which are supplied to a summing section that operates as a modulated current mirror to produce an output signal representative of the input signal. The summing section contains a pair of like-polarity first and second amplifiers (13 and 14) and a pair of like-polarity third and fourth amplifiers (19 and 20 ) complementary to the other amplifiers. A pair of impedance elements (11 and 12) are coupled between a first voltage supply (ground reference) and the third and fourth amplifiers. A pair of current sources, typically impedance elements (8 and 9), are coupled between a second voltage supply (+B) and the first and second amplifiers. An important feature of this circuit is that the output signal changes with the differential portion of the input signal as its common-mode portion varies over the entire voltage range between the levels of the supplies.