Master the design in 5 minutes! Super classic engineer experience

This article shares some of the experience of senior electronic engineers, very classic, let you master the design in 5 minutes!

Essential knowledge of electronic engineers (1)

Operational amplifiers are widely used in analog and digital circuits with simple peripheral components. There are several models of op amps, and there are several differences in detailed performance parameters, but the principle is the same as the application method.

An op amp typically has two inputs, a positive input and an inverted input, and one and only one output. In addition to two inputs and one output, some op amps have several performance-compensating pins.

The resistance of the photoresistor changes significantly as the intensity of the light changes. Therefore, it can be used to make smart curtains, street light automatic switches, camera shutter time auto adjusters, and the like.

A reed switch is an electronic component that can control the on and off of a circuit by a magnetic field. The inside of the reed pipe is composed of soft magnetic metal**. In the case of a magnetic field, the metal ** can gather magnetic lines of force and be subjected to a force to achieve the function of turning on or off.

Essential knowledge of electronic engineers (2)

The role of the capacitor is in three words: "charge and discharge." Do not underestimate these three words, because these three words, the capacitor can pass the alternating current, cut off the direct current; pass the high-frequency alternating current, hinder the low-frequency alternating current.

If the function of the capacitor is in eight words, it is: "Blocking through, the high impedance is low." These eight words are based on the words "charge and discharge", do not understand it does not matter, first memorize hard .

The filter capacitor can be selected according to the output current of the DC power supply and the power requirement of the latter stage (circuit or product). Generally, it is suitable for each 1 amp current corresponding to 1000UF-4700UF.

Essential knowledge of electronic engineers (3)

The role of the inductor is in four words: "Electromagnetic conversion." Do not underestimate these four words, because these four words, the inductor can block the AC, through the DC; through the low-frequency AC, hinder the high-frequency AC. The function of the inductor is then used in eight words: "The traffic is straight, the low impedance is high." These eight words are based on the word "electromagnetic conversion".

The inductor is the dead end of the capacitor. In addition, the inductor has such a characteristic that the current and the magnetic field must exist at the same time. When the current is to disappear, the magnetic field will disappear; the magnetic field will disappear, the current will disappear; the magnetic field will change in the north and south, and the positive and negative currents will also change.

The current and magnetic field inside the inductor have been "playing civil war". The current wants to change, and the magnetic field does not change. The magnetic field wants to change, and the current does not change. However, due to external factors, both current and magnetic fields may have to change. Adding voltage to the inductor coil, the current wants to increase from zero, but the magnetic field will oppose, so the current has to be gradually increased; the voltage is removed from the inductor, the current wants to change from large to zero, but the magnetic field has to be opposed, but the current loop No, the current has been forced to zero, the magnetic field will be angry, and immediately generate a very high voltage across the inductor in an attempt to generate current and maintain the current. This voltage is very high and can even damage electronic components, which is the self-inductance of the coil.

Adding a varying magnetic field to an inductor coil produces a current as long as the coil has a closed loop. If there is no loop, a voltage is generated across the coil. The purpose of generating voltage is to attempt to generate current. When two or more coils share a core (the action of the concentrated magnetic lines) or share a magnetic field, the current and the magnetic field between the coils interact with each other, which is the mutual inductance of the current.

As you can see, the inductor is actually a wire, and the resistance of the inductor to DC is small, even negligible. The inductor exhibits a large electrical resistance to the alternating current.

The series and parallel connection of the inductor is very complicated, because the inductor is actually a wire distributed in a certain position, so the series and parallel connection of the inductor are also related to the position of the inductor (mainly related to the interaction of the magnetic field), if not Considering the effects of magnetic field, distributed capacitance, and wire resistance (Q value), it is equivalent to the series and parallel effects of the resistor.

The higher the frequency of the alternating current, the greater the hindrance of the inductance. The lower the frequency of the alternating current, the smaller the hindrance of the inductance.

When the inductor and the fully charged capacitor are connected in parallel, the capacitor discharge will give the inductor, the inductor will generate a magnetic field, the magnetic field will maintain the current, and the current will reversely charge the capacitor. After the reverse charging, it will discharge again and again. If there is no loss, Or it can supplement this loss in time, and it will produce stable oscillation.

Essential knowledge for electronic engineers (4)

Coupling is the meaning of transmitting signals. Photocouplers are naturally used to complete the transmission of electrical signals. Generally, there is an electronic component that has a light-emitting portion and a receiving portion that are integrated and fabricated. Usually four active pins (ie, four pins are active in the circuit) are a group.

Optocouplers have the advantage of being able to easily isolate the power supply and are most commonly used in primary and secondary isolation of utility power switching power supplies. In addition, there are many applications in computer peripheral communication, and multiple sets of photocouplers (minimum four pins per group) can be integrated in one component.

Piezoelectric ceramic sheets can perform excellent vibration detectors. They are electro-acoustic devices that can hear sound when an audio voltage is applied. When subjected to vibration (mechanical deformation), a weak voltage can be induced.

When welding, properly adjust the welded part, soldering iron tip, solder wire (with flux), make the three points in one, fully contact, when the soldering place has the proper solder and flux, the solder wire should be removed. . The welding process is usually suitable for 2-3 seconds.

Flux: Pine perfume is often used as a flux in the factory. Everyone can make amateur homemade, using industrial alcohol (medical alcohol is more expensive, no need) to melt rosin. Keep an eye out: don't overdo it at a time, and the concentration can be flexibly controlled.

Essential knowledge of electronic engineers (5)

The role and function of the diode is in four words: "unidirectional conduction." Diodes are commonly used for rectification, detection, voltage regulation, clamping, and protection circuits.

A rectifier diode is placed in the power supply circuit of the Walkman. When the DC power supply is connected, no current will be generated and the Walkman will not be damaged.

Adding a forward voltage of less than 0.6V to the diode (silicon data), the diode basically does not generate current (there is no more current in the reverse direction), this voltage is called dead zone voltage, threshold voltage, threshold voltage, conduction Voltage, etc.

The function and function of the triode is completed by four words: "The resistance is variable." Since the resistance value equivalent to the triode can be changed indefinitely, the triode can be used to design a switching circuit, an amplifying circuit, and an oscillating circuit.

The collector current of the triode is equal to the base current multiplied by the amplification factor. When the base current is large enough, the collector current cannot be increased for various reasons. At this time, the collector voltage is already equal to or close to the emitter. The voltage is equivalent to a resistance value of 0 ohms.

Convinced that the triode's amplification state is tricky: the emitter junction is positively biased, and the collector junction is reverse biased.

The triode is a current controlled device, and the FET is a voltage controlled device. FET performance is excellent, but in discrete components, low supply voltage adaptability is worse than triode.

FETs are voltage-controlled devices that are easily damaged by static electricity. Therefore, most of the FETs have protection diodes.

The thyristor is actually a high-speed electronic switch with no mechanical contacts. This switch requires a small current to master. This switch has a self-locking function, that is, after the conduction is removed, the current can still be maintained, and once it is turned off, the off state can be maintained.

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