Inventors:
Mathew A. Rybicki - Austin TX
Todd L. Brooks - Austin TX
Assignee:
Motorola, Inc. - Schaumburg IL
International Classification:
H03F 345
Abstract:
A fully differential line driver circuit (25) includes an input differential amplifier (26) and double-ended differential amplifiers (27, 28). A first output driver stage (29) includes a pair of series connected transistors (30, 31), and a second output driver stage includes a pair of series connected transistors (33, 34). The differential amplifiers (27, 28) provide bias and signals voltages to the gates of the series connected transistors (30, 31, 33, 34). The output stages (29, 32) provide differential output signals for driving a low impedance load. The clamping circuits (35-38) control overlap currents in the output stages (29, 32). Common-mode feedback is used to ensure a common-mode voltage of the differential output signals remains at a predetermined voltage to ensure maximum signal swing and thus, maximum efficiency.