The N-type transistor has its Source terminal cnnected to ground. For an N-type transistor to be ON (conducting), its gate voltage must be higher than its source voltage by an amount known as a threshold. This N-type transistor is said to be on(conducts between terminals Drain and Source) when there is a logic 1 voltage on its Gate. When the Gate is at logic 0, this N-type transistor is said to be OFF and acts as an open circuit between Drain and Source terminals.
