A family of fully-integrated differential amplifiers was designed and fabricated in 6H-SiC, n-channel JFET integrated-circuit technology. A single-stage amplifier with resistor loads has gain-bandwidth of ~2.8 MHz, and differentialmode gain that varies by less than 1 dB from 25-600 o C. A twostage amplifier with current-source loads and common-mode feedback in 1 st -stage, and resistor loads in 2 nd -stage has gainbandwidth of 1.4 MHz, and differential-mode gain of 69 dB at 576 o C, with just 3.6 dB gain-variation from 25-576 o C.

N-channel 6H-SiC depletion-mode junction fieldeffect transistors (JFETs) have been fabricated, and characterized for use in high-temperature differential sensing. Electrical characteristics of the JFETs have been measured and are in good agreement with predictions of an abrupt-junction long-channel JFET model. The electrical characteristics were measured across a 2-in wafer for temperatures from 25 • C to 450 • C, and the extracted pinchoff voltage has a mean of 11.3 V and a standard deviation of about 1.0 V at room temperature, whereas pinchoff current has a mean of 0.41 mA with standard deviation of about 0.1 mA. The change in pinchoff voltage is minimal across the measured temperature range, whereas pinchoff current at 450 • C is about half its value at room temperature, consistent with the expected change in the nμ n product. The characterization of differential pairs and hybrid amplifiers constructed using these differential pairs is also reported. A threestage amplifier with passive loads has a differential voltage gain of 50 dB, and a unity-gain frequency of 200 kHz at 450 • C, limited by test parasitics. A two-stage amplifier with active loads has reduced sensitivity to off-chip parasitics and exhibits a differential voltage gain of 69 dB with a unity-gain frequency of 1.3 MHz at 450 • C.[ 2009-0029]Index Terms-Differential amplifier, high-temperature electronics, junction field-effect transistor (JFET), silicon carbide integrated circuit (IC).

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This paper reports the characterization and modeling of differential amplifiers constructed using integrated 6H-Silicon Carbide (SiC) depletion-mode n-channel JFETs operating at temperatures up to 450 o C, along with offchip passive components. The 3-stage amplifier has a differential voltage gain of ~50 dB and a unity-gain frequency of ~200 kHz at 450 o C, limited by test parasitics. With further improvements in the related interconnect technology, the JFET technology reported here would enable analog sensor interface circuits operating at temperatures as high as 600 o C for use in data acquisition from high-impedance microsensors.Index Terms -differential amplifier, high-temperature, JFET, junction field effect transistor, silicon carbide.