A rectifier diode is used as a one-way check valve. Since these diodes only allow electrical current to flow in one direction, they are used to convert AC power into DC power. When constructing a rectifier, it is important to choose the correct diode for the job; otherwise, the circuit may become damaged. Luckily, a 1N4007 diode is electrically compatible with other rectifier diodes, and can be used as a replacement for any diode in the 1N400x family.
Reverse Voltage Rating
A diode allows electrical current to flow in one direction -- from the anode to the cathode. Therefore, the voltage at the anode must be higher than at the cathode for a diode to conduct electrical current.
In theory, when the voltage at the cathode is greater than the anode voltage, the diode will not conduct electrical current. In practice, however, the diode conducts a small current under these circumstances. If the voltage differential becomes great enough, the current across the diode will increase and the diode will break down.
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Some diodes -- such as the 1N4001 -- will break down at 50 volts or less. The 1N4007, however, can sustain a peak repetitive reverse voltage of 1000 volts.
When the voltage at the anode is higher than the cathode voltage, the diode is said to be "forward-biased," since the electrical current is "moving forward." The maximum amount of current that the diode can consistently conduct in a forward-biased state is 1 ampere.
The maximum that the diode can conduct at once is 30 amperes. However; if the diode is required to conduct that much current at once, the diode will fail in approximately 8.3 milliseconds.
Forward Voltage and Power Dissipation
When the maximum allowable consistent current amount is flowing through the diode, the voltage differential between the anode and the cathode is 1.1 volts. Under these conditions, a 1N4007 diode will dissipate 3 watts of power (about half of which is waste heat).