The Schottky diode (named after German physicist Walter H. Schottky), also known as hot carrier diode, is asemiconductor diode with a low forward voltage drop and a very fast switching action. The cat's-whisker detectors used in the early days of wireless and metal rectifiers used in early power applications can be considered primitive Schottky diodes.

　　When forward current flows through a solid-state diode, there is a small voltage drop across its terminals. A silicon diode has a typical voltage drop of 0.6–0.7 V, while a Schottky diode has a voltage drop of 0.15–0.45 V. This lower voltage drop can be used to give higher switching speeds and better system efficiency.

　　The Shottky diode is often used as a voltage limiter (aka clamp or bypass diode), in reverse bias. This is because the reverse bias voltage, the voltage at which it meaningful reverse leakage occurs, can be made quite low relative to other diode types, and in fact stable and specific. Shottky diodes for this use are sold by their reverse bias voltage spec. The impedance is quite low as with any diode in conducting mode. In effect it becomes a conductor at that voltage, and can be considered to be a switch.. "If reverse bias voltage >= X, then switch on ,otherwise remain OFF". This should not be relied on for high frequencies due to stability issues but the diodes are simply made stable for DC use ( perhaps to PWM frequencies ). The reverse bias voltage will not climb as any increase in current or voltage will simply bypass the protected circuit by easily passing through the diode, and yet if the applied voltage is not high enough, its not conducting.. The voltage is limited to be relatively close to the specified voltage.

　　Voltage clamping[edit]

　　While standard silicon diodes have a forward voltage drop of about 0.6 V and germanium diodes 0.2 V, Schottky diodes’ voltage drop at forward biases of around 1 mAis in the range of 0.15 V to 0.46 V (see the 1N5817[5] and 1N5711[6] datasheets found online at manufacturer's websites), which makes them useful in voltage clamping applications and prevention of transistor saturation. This is due to the higher current density in the Schottky diode.

　　Reverse current and discharge protection[edit]

　　Because of a Schottky diode's low forward voltage drop, less energy is wasted as heat making them the most efficient choice for applications sensitive to efficiency. For instance, they are used in stand-alone ("off-grid") photovoltaic (PV) systems to prevent batteries from discharging through the solar panels at night, called "blocking diodes". They are also used in grid-connected systems with multiple strings connected in parallel, in order to prevent reverse current flowing from adjacent strings through shaded strings if the "bypass diodes" have failed.

　　Switched-mode power supplies[edit]

　　Schottky diode are also used as rectifiers in switched-mode power supplies. The low forward voltage and fast recovery time leads to increased efficiency.

　　They can also be used in power supply "OR"ing circuits in products that have both an internal battery and a mains adapter input, or similar. However, the high reverse leakage current presents a problem in this case, as any high-impedance voltage sensing circuit (e.g., monitoring the battery voltage or detecting whether a mains adapter is present) will see the voltage from the other power source through the diode leakage.