A protection circuit including a multi-gate high electron mobility transistor (HEMT), a forward conduction control block, and a reverse conduction control block is provided between a first terminal and a second terminal. The multi-gate HEMT includes an explicit drain/source, a first depletion-mode (D-mode) gate, a first enhancement-mode (E-mode) gate, a second E-mode gate, a second D-mode gate, and an explicit source/drain. The drain/source and the first D-mode gate are connected to the first terminal and the source/drain and the second D-mode gate are connected to the second terminal. The forward conduction control block turns on the second E-mode gate when a voltage difference between the first and second terminals is greater than a forward conduction trigger voltage, and the reverse conduction control block turns on the first E-mode gate when the voltage difference is more negative than a reverse conduction trigger voltage.