In order for a diode to conduct, it must be:

For a standard semiconductor diode to conduct electricity, a specific voltage polarity must be applied across its terminals. Connecting the positive voltage to the anode and the negative voltage to the cathode is known as 'forward biasing' the diode, which overcomes its internal barrier and allows current to flow freely. If the polarity is reversed (reverse biased), the diode will block current flow. Terms like 'close coupled' refer to the inductive transfer of energy in transformers or tuned circuits, and 'enhanced' refers to the operation of certain field-effect transistors, neither of which apply to basic diode conduction.