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Superior performance of the Silicon Carbide (SiC) semiconductor in high temperature and harsh environment is widely known. However, utilizing the Vertical Channel 4H-SiC JFET (SiC JFET) for analog design exhibits significant design challenges, even at room temperature. The fundamental challenges are low intrinsic gain, the limitation of the Gate to Source Voltage Range (GSVR), and restrictions on utilizing Channel Length (CL) as a design parameter due to fabrication complexity. These challenges must be successfully overcome at room temperature, before moving towards high temperature design. The main objective of this paper is to establish a design base, overcome the challenges, demonstrate the feasibility, and present a novel all SiC JFET based operational amplifier (opamp) that addresses overall performance at room temperature. Before attempting design, Enhancement Mode (EM) and Depletion Mode (DM) SiC JFETs are characterized, analyzed, and modeled for simulation. A unique and reliable four stage opamp configuration is presented that takes design requirements into account, uses threshold voltage in place of CL as a design parameter, and employs gain enhancing design techniques while achieving maximum obtainable frequency response. The final opamp is fabricated and tested and shown to have 66.7 dB DC gain and 5.71 MHz unity gain frequency.

The design of analog integrated circuits, for instance, the operational amplifiers, have been widely perfected with devices and processes available in silicon. However, analogous circuits have been the subject of research in Silicon Carbide (SiC). Among SiC devices, 4H-SiC Lateral-Trench JFET (LTJFET) transistor offers advantages and new opportunities to make affordable and reliable analog integrated circuits for harsh environment. In this paper: (1) SiC LTJFET is characterized for modeling and simulation, (2) effect of temperature variation on SiC LTJFET threshold voltage and small signal parameters are reported, (3) gain performance and small signal parameters of the basic analog circuit block, Common Source (CS) amplifier, based on the variation of the load transistors threshold voltage (Vth) are studied and analyzed, and (4) frequency and transient response of the cascoded CS amplifier (CS-Cas) are reported.