SiGe BiCMOS fully differential amplifier for extreme temperature range applications

A BiCMOS fully differential amplifier was designed for use with a specified power supply of 3.3 V, requiring a 100 muA current bias and utilizing only heterojunction bipolar npn and PMOS transistors because of their demonstrated performance in both extreme temperature ranges (-180degC to +120degC) and radiation-rich environments. One unique feature of this design is that two common-mode feedback circuits were employed to control both the input stage and output stage independently. Regulating the common-mode level between the input and output stages produced better stability over temperature for each stage. Special considerations were taken in the layout to increase the immunity of latch-up and noise and decrease mismatch. The BiCMOS amplifier described successfully demonstrates the use of the commercially available IBM SiGe 5AM process to produce reliable operation in extreme temperature and radiation environments.