A Low-Loss Fully Integrated CMOS Active Probe for Gigahertz Conducted EMI Test

A fully integrated CMOS active probe for characterizing conducted electromagnetic interference (EMI) in the gigahertz range is presented. Based on the direct coupling method of International Electrotechnical Commission standard, the active 1-Omega current probe is designed and realized by a standard 0.18-mu m CMOS technology to overcome a large insertion loss of 34.2 dB in the conventional passive probe. A high-precision on-chip 1-Omega resistance is implemented at the input, followed by a high gain and wideband amplifier in the proposed EMI probe. The measured insertion loss is significantly reduced to similar to 18 dB with a bandwidth up to 3 GHz. Also, the conducted emission of a microcontroller unit is tested, which demonstrates that the proposed active probe could capture very low-level high-frequency interference overlooked by the conventional passive probe.