The role of Schottky diodes and their switching connections

The role of Schottky diodes and their switching connections
The resistance of the Schottky diode is very small under the action of forward voltage, and it is in the conduction state, which is equivalent to a switch-on; Under the action of the reverse voltage, the resistance is very large, and it is in a cut-off state, like an open switch. Using the switching characteristics of Schottky diodes, various logic circuits can be composed. Due to the unidirectional conductivity of Schottky diodes, the PN junction is turned on under positive bias, and the resistance in the conduction state is very small, about tens to hundreds of ohms; UNDER THE REVERSE BIAS, IT IS IN A CUT-OFF STATE, AND ITS RESISTANCE IS VERY LARGE, GENERALLY SILICON SCHOTTKY DIODES ARE ABOVE 10ΜΩ, AND GERMANIUM DIODES ALSO HAVE TENS OF KILOOHMS TO HUNDREDS OF KILOOHMS. Taking advantage of this feature, the Schottky diode will play a role in controlling the current on or off in the circuit, making it an ideal electronic switch.

The most basic switching circuit, in which the two ends of the Schottky diode are connected to Vcc and GND by resistors, respectively, and the Schottky diode is in a state of reverse bias and does not turn on. The AC voltage applied through point C1 cannot pass through the Schottky diode, and the AC component cannot be detected after C2.

The connection of the Schottky diode is reversed from the figure above, and the Schottky diode in the forward conduction state allows the AC signal applied at the C1 point to pass through the Schottky diode and present it at the output of C2. This is the state of the diode when it is turned on, and we can also call it the "on" state of the switch.

This is the simplest circuit that regulates the conduction state of a Schottky diode by a state of DC bias. This enables the control of AC signals. In the practical process, it is usually to ensure that the level of one side is unchanged, and adjust the level of the other side, so as to control the conduction of the diode. In RF circuits, this design is often associated with measures to prevent RF components from mixing into the logic/power lines to reduce interference on the lines that provide bias, but in general this design is common.