As the demand for sensing technology continues to increase across various fields, FET-based biochemical sensors are increasingly being applied in sensing and detection due to their advantages of low noise, low power consumption, easy integration, and miniaturization. However, existing instruments used to measure FET device characteristics generally suffer from drawbacks such as large volume, high power consumption, and unsuitability for versatile experimental environments. Particularly in confined and enclosed experimental settings, the size and power consumption of source meters can significantly impact measurements. To address this issue, this paper explores the operational principles of FETs in sensing and detection and designs a miniaturized detection circuit suitable for FET-based sensing, aimed at meeting the experimental requirements of FET devices in cramped and enclosed measurement environments, thereby replacing bulky instruments for experiments. The paper first investigates the operational principles of FET-based sensing and detection, clarifies that the circuit needs to provide bias voltages for gates, sources, and drains, collect FET channel currents, and achieve data transmission. While ensuring detection functionality and measurement accuracy, efforts are made to minimize the circuit's size. To ensure measurement safety, an ESD (Electro-Static discharge) protection circuit is incorporated to prevent damage to the devices from excessive peak voltages. Following validation tests on critical modules, the entire circuit's application functionality is verified through measurements of transfer characteristics across different FET devices. The design of the miniaturized detection circuit is ultimately completed, and its capability to replace large-scale detection instruments for FET-based sensing experiments is validated. The error between output characteristics and actual measurement should not exceed 1% and 3%, respectively. When testing uA level current, the signal-to-noise ratio can reach over 40 dB.