Bootstrap class-D wideband RF power amplifier

In a Class-D output stage that includes a first field-effect transistor (FET) and a second FET, a method of switching the first FET ON and OFF, comprising:

• providing a bootstrap path including a resistive element between the source and gate of the first FET;
• switching the second FET, which has its drain coupled to the source of the first FET, and a third FET, which has its drain coupled to the gate of the first FET, OFF, in response to a common switch drive signal, to allow a voltage across the bootstrap path to rise to a level greater than a threshold voltage of the first FET and thereby switch the first FET ON;
• biasing the source of the second FET to a first bias voltage;
• biasing the source of the third FET to a second bias voltage that is at least one threshold voltage lower than the first bias voltage;
• and
• switching the second and third FETs ON, in response to the common switch drive signal, to force the voltage across the bootstrap path to a value less than the threshold voltage of the first FET and thereby switch the first FET OFF.