Wide-Temperature Design and Characterization of a SiGe BiCMOS Operational Amplifier for Aerospace Applications

The operational amplifier is a fundamental building block in electronics of all kinds, enabling critical functions such as sensing, signal conditioning, data acquisition, computation, communications, and control. For applications like space and planetary surface exploration, amplifiers must be reliable across extreme temperatures, ranging from near absolute zero$\left(0 ~\mathrm{K},-273^{\circ} \mathrm{C}\right)$to above 125° C. Commercial amplifiers, typically specified for a temperature range no more than$-55^{\circ} \mathrm{C}$to 125° C, are often inadequate in such wide-temperature, high-reliability applications. While some CMOS amplifiers can function at cryogenic temperatures, bandgap-engineered materials and devices can offer superior stability, reliability, and radiation tolerance. This work presents both the design of a two-stage operational amplifier in a commercial 90 nm BiCMOS process featuring silicon-germanium heterojunction bipolar transistors (HBTs), and the development of a flexible wide-temperature test apparatus capable of characterizing both commercial off-the-shelf (COTS) amplifiers and custom IC amplifiers across a broad temperature range spanning at least$-180^{\circ} \mathrm{C}$to 125° C. The test system enables measurement of five critical amplifier parameters across temperature: DC open-loop gain, gain-bandwidth product, input-referred offset voltage, DC common-mode rejection ratio (CMRR), and DC power-supply rejection ratio (PSRR). Experimental validation demonstrates the amplifier's stable operation from$-180^{\circ} \mathrm{C}$to 125° C, with additional in situ measurements confirming functionality at$4.2 ~\mathrm{K}\left(-269^{\circ} \mathrm{C}\right)$as part of a linear voltage regulator (LVR) supplying power to an X-band RF low noise amplifier (LNA).