A GaN-based Current Sense Amplifier for GaN HEMTs with Integrated Current Shunts

This work shows a GaN-based current sense amplifier as a readout circuit for a power GaN HEMT with integrated current shunt. In the GaN power transistor, the voltage drop of the outermost metal finger of a large-area comb structure effectively realizes a shunt acting as a current sensor. This small voltage drop of the integrated shunt (approx. 4 mV/A at $100 \mathrm{m}\Omega$ on-resistance) is amplified by a two-stage GaN-based amplifier with a gain of $\gt 40$ dB at room temperature. The amplifier consisting of two series-connected differential amplifiers with source follower intermediate stages was verified in a double pulse test setup up to a peak current of 11.5 A. Consequently, the proposed current sense amplifier allows a simple and potentially integratable further processing for the monitoring or control of the current signal.