Silicon Carbide Bipolar Analog Circuits for Extreme Temperature Signal Conditioning

This paper presents functional high-temperature analog circuits in silicon carbide bipolar technology. The circuits will collectively form the analog signal conditioning block for a wireless telemetry system in an extreme environment (above 400°C). The signal conditioning block is composed of a low dc gain operational amplifier, a negative voltage charge pump (CP), an RC oscillator, and a voltage regulator. The circuits are tested up to 450°C. The measured open-loop gain for the amplifier at 450°C is 30 dB. The regulator provides approximately 9-V output at 450°C for a fixed load current of up to 18 mA and an applied reference of 4.5 V. The negative voltage CP requires an oscillating signal at its input, which is provided by the RC cross-coupled oscillator. The CP provides about -5 V at 450°C.