Square-law clamping circuit in MOS technology

摘要

A regulated BICMOS output buffer (34) improves interfacing to loads such as 3.3 volt integrated circuits. The output buffer (34) provides a first voltage to a base of a pullup transistor (116) in response to a difference between an input voltage and a reference voltage. An emitter of the pullup transistor (116) provides an output signal. A second transistor (102) having characteristics matching those of the pullup transistor (116) receives the first voltage at its base, and provides the input voltage at its emitter. The output buffer (34) changes the first voltage until the voltage at the base of the second transistor (102) equals the reference voltage. Thus, signal reflections on the output signal do not affect the performance of the output buffer. Clamps (99, 120) coupled to the base and emitter of the pullup transistor (116) provide soft clamping according to a square law.