Saturday, 29 August 2015


Photodiode is a way to light according to use, into a current or voltage signal light detector.  Common conventional solar cells are through a large area of the photodiode to produce electricity.
Photodiode with the conventional semiconductor diodes are similar, but the photodiode can be directly exposed in the vicinity of the light source or through a transparent small window, optical fiber package, to allow light to reach the light-sensitive area of this device to detect light signals. Many used to design a photodiode using a PIN diode junction, rather than the general PN junction, to increase the response speed of the device on the signal. Photodiodes are often designed to operate in a reverse bias state.

Infrastructure is typically a photodiode PN junction or a PIN junction. When a photon with sufficient energy shock to the diode, it will excite an electron to produce free electrons and there is a positively charged holes. Such a mechanism is also known as photoconductivity. If the photon absorption occurs in the junction depletion layer, the internal electric field in the region will eliminate the barriers between them, so that the hole can move in the direction of the anode, cathode electrons toward the direction of motion, so the photocurrent arises. The actual dark current and photocurrent is integrated light generated current, and therefore the dark current must be minimized to improve device sensitivity to light.

Photovoltaic mode

When the current bias is 0:00 photodiode in photovoltaic mode, then out of the photodiode is suppressed ends a potential difference accumulated to a certain value. (Solar cell)

Photoconductive mode

When operating in this mode, the photodiode is reverse biased often dramatically reduces the response time, but the noise had to increase the cost. At the same time, the width of the depletion layer is increased, thereby reducing the junction capacitance, also makes it possible to reduce the response time. Reverse bias will cause small amounts of current (saturation current), the current and the photocurrent in the same direction. For specific spectral distribution between the photocurrent and the incident light is linearly proportional to the luminance.

Other operating modes

 Conventional of avalanche photodiode having a structure similar to a photodiode, but requires much higher reverse bias voltage. This will allow the carriers of light generated by the avalanche breakdown substantial increase, resulting in internal gain in the photodiode inside, thereby further improving the response rate of the device.

Thursday, 27 August 2015

Magnetic-core memory

Magnetic-core memory

Magnetic-core memory (English: Magnetic Core Memory) is an early form of computer memory. Magnetic-core memory using memory-magnetic material, its principle is: the magnetic ring (core) with magnetic or non-magnetic properties of the state, to represent the 1 or 0 bit, a long string of 1 or 0 on behalf of the combination of information to be stored.

Magnetic-core memory is a random access memory (Random Access Memory), the computer can assume the role of main memory. Compared to the vacuum tube, the magnetic-core memory power, nor life issues vacuum tube. When the computer into the semiconductor era, there is still a considerable period of time, magnetic-core memory continued role as the main memory. Also, because the magnetic-core memory is non-volatile memory (Non-volatile Memory), one of its features are: Even when the machine or power outage, as long as there are no errors write signal occurs, still can retain its contents.

For magnetic-core memory have an important contribution to the Dr. Wang An, who is also the founder of Wang Laboratories. He invented a reading that is written (write-after-read cycle), to solve one of the important issues on the core body application that will be read at the same time can not erase the memory retains data problems, and later made the relevant patent.
Although the semiconductor memory used today has been a long, but sometimes still use the traditional name, also known as Memory Core, one obvious example is the Core Dump: In the program crashes and abort to save main memory contents up to for debugging purposes.

Sunday, 23 August 2015



Magnet can attract iron and its outer magnetic field is generated objects. Magnet means narrow magnetite ore products, broadly refers to the use of magnets to generate a magnetic field of an object or device. As a magnetic dipole magnet that attracts ferromagnetic materials such as iron, nickel and cobalt and other metals.  Poles are judged by a thread hanging magnet, called the finger pointing to the North Pole or N-pole, pointing to the South Pole as a guide pole or S pole. (If you want to become a big magnet Earth is currently Earth's magnetic north pole is S pole, the geomagnetic South Pole is the N pole.) Magnet is different poles attract, with the exclusion pole. And refers to the Arctic polar attraction guide, guide pole and guide poles repel, repel finger Arctic and Arctic finger.

Permanent magnets and magnet divided into non-permanent magnets. Natural, also known as lodestone permanent magnet, a permanent magnet may be manufactured by hand (the strongest magnets are neodymium magnets). Only non-permanent magnets have magnetic properties under certain conditions, usually in the form of electromagnets to produce, that is, the use of electric current to strengthen its field.

Non-magnetized magnet inside the magnetic molecules (molecular magnets theory) is randomly arranged, arranged in the magnetization process after the magnetic molecules have rules. In this case, N pole and S pole magnetic molecules will be facing in the same direction so that the magnet has a magnetic and become magnets. At the same time, the presence of the opposite poles of the magnetic poles and an equal amount on the same magnet.



Loudspeakers name suggests is the sound amplification, spread farther mean relatively speaker, microphone sound more penetrating.
Loudspeaker according to its size, usage and purpose can be divided into various types, each with their use advantage. Due to the shape and size of portable loudspeakers, speakers’ constraints, general power is only 3--8W. The wireless microphone wired microphone and volume sizes are various different purposes, and smaller size for teachers, tour guides used to hang at the waist, both hands to play more freely, its power is generally also 3W-8W. Bulky for outdoor activities, summer camps, extracurricular lectures and other high traffic areas, the power at 35W --- 95W. Lithium battery according to the type of loudspeaker is made using a classification. It solves the problem of pollution on the environment of traditional batteries, which is used mainly in the mobile phone supply lithium-ion technology to the loudspeaker.

Traditional loudspeakers, through universal, homogeneous competition in recent years, have brought the market price shopping, so that companies are increasingly emphasis on cost rather than quality. Blind pursuit of cost, not only contribute to sound quality cannot be improved, but also makes noise noise increases, to bring a certain degree of physical and mental damage to the user.

Poor sound quality, cannot meet the standard of living has been increasing gradually increasing consumer demand, the market needs to product upgrades. The new "sub-spreader" because the use of crossover broadcast technology to effectively solve the traditional loudspeaker sound rushed, fried, thick, shortcomings. You can enhance the soft and delicate, reduce noise, so sound quality is more stress. The audience does not cause dizziness, irritability, rapid heartbeat, high blood pressure, and entertainment at the same time to feel more pleasure, more physical and mental health. Sub-spreader enables high bass harmony echo, microphone input sound, but also can play a more realistic sound, so seize the audience, enhance the sense of affinity.

Wednesday, 19 August 2015

Hybrid integrated circuits

Hybrid integrated circuits

Hybrid integrated circuits are then integrated semiconductor integrated circuit external components, or said secondary integration. It is composed of a semiconductor integrated process and thick (thin) film technology combined and integrated circuits made of semiconductor integrated circuits, it is also one of the miniaturization of electronic equipment, the main way to achieve.

Hybrid integrated circuits including the thick-film, hybrid integrated circuits and thin film, thick-film hybrid integrated circuits. Thick-film hybrid integrated circuits is an insulating substrate (typically ceramic) as the substrate of the circuit, and the first conductor network resistance, capacitance and other components using serigraphy, plasma spraying and other craft printed on the substrate surface, then use the WB, TAB , FCB and reflow soldering and other processes, the other components (such as integrated circuits, sensors, other functional elements, etc.) assembled on a ceramic substrate, and then connect the output pin, and finally as a whole package, the formation of a fully functional circuit products. Known as a thick film integrated circuit or directly called thick.

Film hybrid integrated circuit is the use of thin-film vacuum deposition techniques, sputtering, photolithography and other basic process, the electronic components of the circuit in the form of film products in the production of circuits formed on an insulating substrate.

Tuesday, 18 August 2015

Programmable DC Electronic Load

programmable DC Electronic Load

Programmable DC Electronic Load is the principle of the flux guide or the control of the power MOSFET transistors (duty ratio of the size of the volume), the power dissipated by the power consumption of the power tube apparatus which can accurately detect the load voltage, load current precise adjustment, while analog load short-circuit, an analog resistive and inductive load is capacitive, capacitive load current rise time. Debugging detect general switching power supply is indispensable.

Programmable DC electronic load can simulate real-world loads (appliances). It has a constant current, constant resistance, constant voltage and constant power capabilities, as well as short circuit, over current, dynamic, etc., it should be said that all power manufacturers will be useful, but also must have. Electronic load into DC electronic load and AC electronic load, electronic load due to the application surface problem, this paper introduces the DC electronic loads.

1. Voltage, current and power of choice

According to the output characteristics of the device under test to select electronic load: voltage, current, power and accuracy of the testing requirements. Programmable DC Electronic Load Module can only work when tested alone or parallel operation, the series for the module is very dangerous. So ideal state is that all requirements are within the range single group, followed by multiple modules connected in parallel to achieve the selection. That is, when the voltage of the selected module must meet the test requirements. Individual modules or the full sum of the current and power box is installed to meet the testing requirements.

2. Accuracy and resolution choices

Accuracy and resolution is an important parameter index electronic load. Meaning accuracy of different representations of programmable DC electronic load.

Friday, 7 August 2015



Capacitor referred capacitors; it is also a major element of the electronic circuit components. It can store electrical energy, with the charge, discharge and through the exchange, DC-blocking properties. In a sense, a bit like a capacitor battery. Although both work in very different ways, but they can store energy.

Battery has two electrodes inside the battery, so that a chemical reaction to produce electron electrode, the other electrode of the electron absorption. The capacitor will have a much simpler, it does not produce electron - it just to store electrons. It is one of the indispensable basic elements of the extensive use of various types of electronic equipment. Various capacitors in the circuit can play different roles, such as coupling and DC blocking, bypass, rectifier filter, high-frequency filter, tuning, storage and division and so on. The capacitor should be selected according to the circuit voltage, frequency, waveform, AC and DC components of temperature and humidity conditions.
Capacitor, typically referred to its ability to hold a charge capacitance, denoted by the letter C.   Capacitors, by definition, is 'loaded container electricity', it is a device receiving the charge. English name: capacitor. Capacitor is one of a large number of electronic components used in electronic equipment; it is widely used in the circuit compartment straight cross-connection, coupling, bypass, filtering, tuning circuits, energy conversion and control.

The capacitance of the capacitor is different. Capacitance basic physical quantities, the symbol C, the unit is F (farad).

General formula C = Q / U parallel plate capacitor special formula: electric field strength between the plates E = U / d, the capacitor capacitance of the formula C = εS / 4πkd.

Thursday, 6 August 2015

Amplitude modulation

AM Signals

Amplitude modulation (AM) also referred to as amplitude, by varying the amplitude of the output signal, to achieve the purpose of transmitting information. General changes in the amplitude modulation of the high-frequency end of the output signal and the original signal into a certain function, demodulation end demodulates and outputs the original signal.

In fact, a function is generally proportional relationship. The greatest benefit of this modulation is the modulation and demodulation is very simple, just a diode and a capacitor can, of course, the biggest drawback is the relatively large distortion, while more sensitive to interference, relatively speaking, is a relatively old technology. But technology does not mean that the old applications are not widespread, there are still many areas of application, such as a radio (AM radio) and Aeronautical Radio, Especially in the field of aviation radio, the traveling speed of the aircraft very quickly, quicker fighter, for FM, the Doppler effect is too big, it will affect communications, and AM is not affected by the Doppler effect, it can not be replaced. At the same time there are some improvements AM techniques, such as single sideband modulation (also known as single sideband), residual sideband modulation (Vestigial Side Band, VSB), and amplitude modulation multiple variants such as the current amplitude is widely used in a mobile communication digital modulation.

Saturday, 1 August 2015

Dipole antenna

Dipole antenna

Dipole antenna used to transmit and receive signals of fixed frequency. Although the usual measurements are used in wideband antenna, but the venue and the measurement antenna attenuation coefficients are required to use a dipole antenna. Dipole antenna in the frequency range 30MHz ~ 4GHz. Which is a set of precise VHAP and UHAP dipole antenna is especially suitable for measuring site attenuation and antenna factor. Meanwhile, the antenna for the Japanese VCCI standards organizations designated only dedicated antenna anechoic chambers and open-field site attenuation measurement and the like. The antenna is used by many laboratories, as antenna standard laboratories.

Vertical antenna is actually a dipole antenna. Dipole antenna consists of two conductors, each 1/4 wavelength, i.e., the total length of a half wavelength of the antenna. So dipole antenna, also called half-wave dipole. The transducer can be a dipole antenna horizontal position, vertical position may be. Its pattern to the feeding point of symmetry. Feed point in the center of the half-wave vibrator. Feed point impedance is purely resistive, approximate 75Ω (approximately 73Ω). If the two 1/4 wavelength resonator extended and then folded back to the center, and joined together, then it became a folded dipole antenna, referred to as folded vibrator.

Folded dipole antenna impedance is purely resistive approximate 300Ω (about 290Ω), shows a high input impedance, high impedance transmission antenna feeder parallel constitute use in many occasions. The dipole antenna straight up, perpendicular to the ground, then a vertical antenna. If the "remove" the lower part of the 1 / 4λ oscillator, the asymmetrically vertical antenna. Common vertical antenna are asymmetric antenna, isotropic in the horizontal direction.
A special.This antenna has a special name called Marconi antenna. R7000 receiver and other antenna configurations belong to this antenna.