We all know that diodes are very small, some are as small as needles, but they are very useful, The application fields are also very wide. Diodes are used in LED lights, electronic appliances, train and car electronic system components, circuit boards and so on. What are the classification, functions and working principles of diodes? Today, Yingzhan electronic components will share with you. In addition, by the way, we will introduce the most widely used diodes in daily life One of the models, I hope to help you
Diode classification: rectifier diode, detector diode, photodiode, light-emitting diode, constant current diode, voltage regulator diode, double base diode, magnetic sensitive diode, precision diode, tunnel diode, varactor diode, Schottky diode, chip diode, photodiode, semiconductor diode, current limiting diode, etc.
Function of diode:
1. Rectifier diode.
With the unidirectional conductivity of diode, alternating alternating alternating current can be transformed into pulsating direct current in a single direction. 2. As a switching element.
Under the action of forward voltage, the resistance of diode is very small and it is in the on state, which is equivalent to an on switch; under the action of reverse voltage, the resistance is very large and it is in the off state, which is like an off switch. Various logic circuits can be formed by using the switching characteristics of diodes.
3. As limiting element.
The forward voltage drop of the diode remains unchanged (0.7V for Si and 0.3V for GE). Using this characteristic, as a limiting element in the circuit, the signal amplitude can be limited in a certain range.
4. Relay diode.
The inductive relay plays an important role in inductive power supply.
5. Detector diode.
It plays a detection role in the radio.
6. Varactor diode.
It is used in the high frequency head of TV set.
Knowledge point extension:
Working principle of diode:
The crystal diode is a p-n junction formed by p-type semiconductor and n-type semiconductor. Space charge layers are formed on both sides of the interface, and a self built electric field is built. When there is no applied voltage, the diffusion current caused by the carrier concentration difference on both sides of the p-n junction is equal to the drift current caused by the self built electric field, so it is in an electrical equilibrium state
① When there is a positive voltage bias, the external electric field and the self built electric field suppress each other and increase the carrier diffusion current, resulting in the positive current.
② When there is a reverse voltage bias, the external electric field and the self built electric field are further strengthened to form a reverse saturation current I0 which is independent of the reverse bias voltage in a certain range of reverse voltage.
③ When the applied reverse voltage is high to a certain extent, the electric field strength in the space charge layer of p-n junction reaches the critical value, resulting in the multiplication process of carriers, a large number of electron hole pairs and a large number of reverse breakdown current, which is called diode breakdown phenomenon.
Introduction to diode IN4007:
IN4007 is a standard recovery diode. The package is diode0.4. Number of pins: 2.
According to the American semiconductor device model naming method, it should be 1N4007 instead of IN4007.
IN4007 parameters
Maximum input reverse peak voltage: 1000V
Maximum input reverse average voltage: 700V
Rated output current, if average: 1A
Maximum forward conduction voltage at 25 ℃ of 1A AC: 1.1V
Forward surge current, IFS Max: 30A
Total power: 2.5W
Number of pins: 2
Junction temperature, TJ maximum: 175 ° C
Surface mount devices: axial leads
General plastic encapsulated rectifier diode 1N4007
Reverse voltage 50 — 1000 V
Forward current 1.0 A
·Low reverse leakage current
·High forward surge capability
·High temperature welding guaranteed:
260 ℃ / 10 seconds, 0.375 “(9.5mm) lead length.
260℃/10 seconds, 0.375” (9.5mm) lead length,
·The lead can withstand 5 pounds (2.3kg) tension. 5 lbs. (2.3kg) tension
Mechanical data
·Terminals: plated axial leads
·Polarity: color band denotes cathode end
·Mounting position: any
Limit value and temperature characteristic TA = 25 ℃ unless otherwise specified