Linear transconductance amplifier operable at low supply voltages using transistors with differing emitter areas

摘要

A bipolar OTA having a wide input voltage range is provided without increasing the circuit scale and current consumption. This OTA includes first to n-th differential pairs of first to 2n-th bipolar transistors whose emitters are coupled together, where n * ------ solidus * 2; and a common current source/sink connected to the emitters of the first to 2n-th transistors. The first to 2n-th transistors are driven by a common tail current produced by the common current source/sink. The transistors of each of the second to n-th differential pairs have a same emitter area K 1 to K n-1 times as large as that of the first and second transistors, where K 1 to K n-1 1. A first input voltage as an input signal to be amplified is differentially applied across bases of the first and second transistors of the first differential pair. A second to n-th input voltages are differentially applied across corresponding bases of the third to 2n-th transistors, respectively. Each of the second to n-th input voltages is produced by attenuating the first input voltage. First to (n-1)-th pairs of dc offset or tuning voltages are applied to the bases of the third to 2n-th transistors, respectively. An amplified output signal is differentially derived from collectors of the first and second transistors.