This paper proposes a three-stage op amp based on the SOI (silicon-on-insulator) process, which achieves a low offset voltage and temperature coefficient across a wide temperature range from −40 °C to 250 °C. It can be used in aerospace, oil and gas exploration, automotive electronics, nuclear industry, and in other fields where the ability of electronic devices to withstand high-temperature environments is strongly required. By utilizing a SC (Switched Capacitor) notch filter, the op amp achieves low input offset in a power-efficient manner. The circuit features a multi-path nested Miller compensation structure, consisting of a low-speed channel and a high-speed channel, which switch according to the input signal frequency. The input-stage operational amplifier is a fully differential, rail-to-rail design, utilizing tail current control to reduce the impact of common-mode voltage on the transconductance of the input stage. The two-stage operational amplifier uses both cascode and Miller compensation, minimizing the influence of the feedforward signal path and improving the amplifier’s response speed. The prototype op amp is fabricated in a 0.15 µm SOI process and draws 0.3 mA from a 5 V supply. The circuit occupies a chip area of 0.76 mm². The measured open-loop gain exceeds 140 dB, with a 3 dB bandwidth greater than 100 kHz. The amplifier demonstrates stable performance across a wide temperature range from −40 °C to 250 °C, and exhibits an excellent input offset of approximately 20 µV at room temperature and an offset voltage temperature coefficient of 0.7 μV/°C in the full temperature range.

Achieving coherent sampling has always been a major challenge in analog-to-digital converter (ADC) spectral testing. If the coherent sampling condition cannot be met, leakage appears in the spectrum, which results in inaccurate parameters. The windowing method is widely used to process ADC data to eliminate leakage. However, this method requires prior knowledge about the type of window, and some commonly used windows cannot provide accurate results for a high precision ADC. In this paper, some general principles for optimizing the cosine-sum window and some windows with maximum side-lobe decay have been presented. A test method for eliminating the leakage caused by non-coherent sampling is also proposed. The proposed method can accurately evaluate the dynamic parameters of an ADC with arbitrary non-coherency. Various simulation results and measurement data demonstrate the functionality and robustness of the proposed method. The proposed method significantly relaxes the condition of coherent sampling and decreases the test cost.