Patent ID: 7782099

Claim:
A switching circuit, comprising: a normally-off type first active device of a wide band-gap semiconductor having a first threshold voltage of two volts or less and first and second electrodes and a first control electrode; a driving pulse generating circuit that supplies pulses to the first control electrode; and a normally-on type second active device having third and fourth electrodes connected to said first control electrode and said first electrode of said first active device, respectively, and a second control electrode connected to receive a first control voltage from a circuit associated with the driving pulse generating circuit while the driving pulse generating circuit supplies said pulses, the first control voltage being of a magnitude to turn off the normally-on type second active device to prevent it from conducting, wherein when the driving pulse generating circuit does not supply said pulses, the second control electrode receives a second control voltage from the circuit associated with the driving pulse generating circuit that is of a magnitude to cause the normally-on type second active device to turn on and maintain the first active device of normally-off type stably off even in the presence of noise voltages at the first or second electrodes.