The invention discloses heterojunction compound semiconductor protection clamps and methods of forming the same. A protection clamp is provided between a first terminal and a second terminal, and includes a multi-gate high electron mobility transistor (HEMT), a current limiting circuit, and a forward trigger control circuit. The multi-gate HEMT includes a drain/source, a source/drain, a first depletion-mode (D-mode) gate, a second D-mode gate, and an enhancement-mode (E-mode) gate disposed between the first and second D-mode gates. 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 trigger control and the current limiting circuits are coupled between the E-mode gate and the first and second terminals, respectively. The forward trigger control circuit provides an activation voltage to the E-mode gate when a voltage of the first terminal exceeds a voltage of the second terminal by a forward trigger voltage.