After the Ui reaches 5v, Uo is clamped by the power supply voltage, and the voltage of the voltage source is measured. The rest of the Ui voltage is shared by the resistor R. Before the input voltage Ui reaches 5v, the diode is not turned on, and the output voltage Uo is the measured input voltage UI. After the Ui reaches 5v, the measured voltage is the voltage after the Ui is pulled down, that is, the bidirectional amplitude limit is 5V. Of course, this is an ideal diode without voltage drop.

Principle:

In principle, the modulation signal extracted from the input signal is detected, and the output current is less than1000 mA, which is usually called detection based on the magnitude of the rectified current (1000 mA).

Germanium material is a point contact type, the working frequency can reach 400MHz, the forward voltage drop is small, the junction capacitance is small, the detection efficiency is high, and the frequency characteristics are good, so it is 2AP type. Diodes used for detection, such as touch diodes, can be used not only for general diode detection, but also for limiting, limiting, modulation, mixing and switching circuits. There are also two diode components with good consistency for FM detection.

AM signal is a high-frequency signal carrying low-frequency signals, and the envelope of AM signal is a baseband low-frequency signal. If the average value is taken in each signal period, it will always be zero.

If the amplitude modulation signal passes through the detection diode, the negative part of the amplitude modulation signal is truncated, leaving only the positive part. At this time, if the average value is taken in each signal period (low-pass filtering), the envelope of the amplitude-modulated signal is the baseband low-frequency signal, and the demodulation (detection) function is realized.

Refer to the above? Baidu encyclopedia-detector diode