Differential input driver using current feedback and cross-coupled common base devices

Abstract

A differential input driver circuit () includes first and second transistors (Q, Q) as input transistors and third and fourth transistors (Q, Q) as diode-connected, cross-coupled transistors. In one embodiment, first, second, third and fourth transistors are NPN bipolar transistors. The base terminals of the first and third transistors are connected while the base terminals of the second and fourth transistors are connected. The input transistors receive a pair of differential input signals (In+/−) at the emitter terminals () and provides a pair of differential output signals (Vo+/−) at the collector terminals (). The emitter terminals of the diode-connected transistors (Q, Q) couple the input signal at the emitter terminal of the first transistor to the collector terminal of the second transistor and vice versa. The cross-coupling of the third and fourth transistors enables the input driver to operate effectively in single-ended to differential conversion mode.