A power device, comprising: a normally-off power transistor (Q1) comprising a gate (G), a source (S), and a drain (D); a control terminal electrically connected to the gate (G); a first load terminal electrically connected to the drain (D); a second load terminal electrically connected to the source (S); a Kelvin-source (KS) terminal ; and a failsafe pulldown circuit comprising: a normally-on pulldown transistor (Q2) configured to short the gate (G) to the source (S) when no voltage is applied across the control terminal and the KS terminal , and comprising a pulldown gate, a pulldown source, and a pulldown drain; and a pulldown control circuit connected between the pulldown gate and the pulldown source, and configured to autonomously apply a negative voltage to the pulldown gate, relative to the pulldown source, when a turn-on voltage is applied between the control terminal and the KS terminal, and to autonomously discharge the negative voltage when the turn-on voltage is not applied between the control terminal and the KS terminal, wherein the normally-off power transistor (Q1) is an enhancement-mode Gallium Nitride, GaN, High Electron Mobility Transistor, HEMT, implemented as a Gate Injection Transistor, GIT. a normally-off power transistor (Q1) comprising a gate (G), a source (S), and a drain (D); a control terminal electrically connected to the gate (G); a first load terminal electrically connected to the drain (D); a second load terminal electrically connected to the source (S); a Kelvin-source (KS) terminal ; and a failsafe pulldown circuit comprising: a normally-on pulldown transistor (Q2) configured to short the gate (G) to the source (S) when no voltage is applied across the control terminal and the KS terminal , and comprising a pulldown gate, a pulldown source, and a pulldown drain; and a pulldown control circuit connected between the pulldown gate and the pulldown source, and configured to autonomously apply a negative voltage to the pulldown gate, relative to the pulldown source, when a turn-on voltage is applied between the control terminal and the KS terminal, and to autonomously discharge the negative voltage when the turn-on voltage is not applied between the control terminal and the KS terminal, wherein the normally-off power transistor (Q1) is an enhancement-mode Gallium Nitride, GaN, High Electron Mobility Transistor, HEMT, implemented as a Gate Injection Transistor, GIT. a normally-on pulldown transistor (Q2) configured to short the gate (G) to the source (S) when no voltage is applied across the control terminal and the KS terminal , and comprising a pulldown gate, a pulldown source, and a pulldown drain; and a pulldown control circuit connected between the pulldown gate and the pulldown source, and configured to autonomously apply a negative voltage to the pulldown gate, relative to the pulldown source, when a turn-on voltage is applied between the control terminal and the KS terminal, and to autonomously discharge the negative voltage when the turn-on voltage is not applied between the control terminal and the KS terminal, wherein the normally-off power transistor (Q1) is an enhancement-mode Gallium Nitride, GaN, High Electron Mobility Transistor, HEMT, implemented as a Gate Injection Transistor, GIT. <EOS>