Field effect tube to note what

( 1) for safe use of field effect tube, the circuit design of power dissipation can not exceed the maximum pipe, drain to source voltage, maximum gate voltage and maximum current and other parameters of the limit value.
( 2) MOS field effect tube as the input impedance is very high, so the transport, storage must be leading-out feet short, use the metal shielding packaging, to prevent the external gate breakdown induced potential. Pay attention to, not MOS field effect tube into the plastic box, saving best placed in a metal box, also want to pay attention to the moisture barrier tube.
( 3 ) the use of VMOS must be added the right radiator. In the case of VNF306, the pipe installation of 140 x 140 x 4 ( mm ) of the radiator, the maximum power can reach 30W.
( 4) the type field effect tube when in use, are in strict accordance with the requirements of the biasing access circuit, to abide by the FET bias polarity. Such as the JFET gate source and drain is a p-n junction, N channel tube grid not with positive bias; P channel tube grid with negative bias, etc..
( 5) in order to prevent the FET gate induced breakdown, all test equipment, workbench, electric iron, the line itself must have a good grounding pin; when welding, welding source; in the connected into the circuit before, of all lead end keep each other short connected condition, after welding the shorting material removed from components; shelf tube, should be appropriately ensure the ground such as the use of grounding ring; of course, if the use of advanced gas heating type electric iron, welding field effect tube is more convenient, and ensure the safety of; without power off time, absolutely can't put tube inserted or pulled out from the circuit circuit. The above safety measures in the use of field effect tube must note.
( 6) mounted on the field effect tube, pay attention to the installation position to avoid close to the heating element; in order to prevent pipe vibration, it is necessary to tube shell fastened together; pin lead bend, shall be greater than the root size 5 mm, in order to prevent breakage and leakage caused by tube feet.
( 7) welding, soldering iron shell must be fitted with an external ground wire, in order to prevent the electric soldering iron is charged and damage to the tubes. For a small electric iron welding, can also be hot after pull the plug or power off after welding. Especially in the welding of insulated gate field effect tube, according to the source / drain and gate sequence welding, and welding power.
( 8) multi-pipe parallel connection, because the interelectrode capacitance and the distributed capacitance of a corresponding increase, make the amplifier performance deterioration, through feedback is easy to cause the amplifier high frequency parasitic oscillation. For this purpose, the parallel composite pipes are generally not more than 4, and in each tube base or gate in series connection parasitic oscillation resistance.
( 9) JFET gate to source voltage can not be reversed, can be in the open state of preservation, and the insulated gate type field effect tube when not in use, due to its very high input resistance, to each electrode short circuit, so as to avoid the effect of external electric field and the tube damage.
( 10) 25W electric soldering iron welding should quickly, if use 45～ 75W electric soldering iron, used a pair of tweezers to clamp the tube foot root to help dissipate heat. Junction type field effect tube available sheet resistance profile of qualitative check the quality ( check the PN junction is reverse resistance and leakage between the source and the resistor value ), and the insulated gate field effect tube can not use a multimeter to check, must use the tester, and the tester can remove the access of each electrode shortest route. When removed, you should first short circuit is removed, the key to avoiding gate hanging.
The requirements of high input impedance occasions when in use, must take measures to avoid the influence of the temperature moisture, so that the FET input resistance decreased. If the four lead in the field effect tube, the substrate should be grounded wire. Ceramic encapsulated sesame tube having photosensitive properties, attention should be paid to avoid light use.
For power MOSFET, want to have good heat dissipation condition. Because the power MOSFET in the high load condition use, must be designed to ensure adequate radiator, shell temperature does not exceed the rated value, enabling the device to long-term stable and reliable work.
In short, to ensure the safe use of field effect tube, matters needing attention are diverse, safety measures is various, the majority of professional and technical personnel, especially the majority of electronic enthusiasts, according to its own actual situation, take practical and feasible method, the safe and effective use of field effect tube.

Field effect tube electrical characteristics

Field effect transistor and transistor in the electrical characteristics of the main difference is the following:Patch FET1: the field effect tube voltage control device, the conductive case depends on the gate voltage. Transistor is the current control device, the conductive case depends on the size of the base current.2: the field effect tube current IDS and the grid UGS Gm decided by the relationship between the transconductance, transistor current Ic and Ib by the relationship between amplification coefficient βdecision. That is to say, the field effect tube capable of amplifying Gm measure, transistor capable of amplifying the use of βmeasure.3: FET input impedance, input current is small; the transistor input impedance is very small, in the conductive when larger input current.4: the FET drain source static volt-ampere characteristic with gate voltage UGS variables, transistor characteristic curve to the base current of Ib variables.5: general field effect tube with small power, high power transistor.

Mainland manufacturers have a serious absence of upstream components in the mobile phone market

Inject vibrancy of a huge mobile phone market to the entire mobile phone industry chain. In 2006, global mobile phone production will exceed one billion Chinese production in about 300 million to 400 million. More than 70% of the output value is created by the by phone upstream parts manufacturers.In this huge market, even though magically ran a Chinese enterprise - AAC Acoustics, but in the upstream parts industry in the entire mobile phone, the vast majority of parts manufacturers in the industry chain endings, making a small profit. struggling on the edge of survival and death.Shui Qing Mu Hua, research director ZHOU Yan Wu pointed out that due to the accumulation of technology and other aspects of the mainland factory upstream components in the mobile phone market, the absence of severe, 95% of the market occupied Europe, the United States, Japan, China Taiwan manufacturers.Market share is not optimisticPhone components can be divided into active components (semiconductor components and display), the passive components (capacitors, inductors and resistors), structure (cell phone case and the PCB), the functional components (electro-acoustic components, vibration motors, display, batteries, antennas) of four categories.Among them, semiconductor components include baseband, memory, application processor, power management, radio, camera modules, etc., probably account for more than 50 percent of the cost of handsets, and this part is dominated by U.S. and European companies, such as Texas Instruments, Qualcomm, Ericsson, NEC and Britain Feiling and so on."High threshold of the semiconductor component manufacturers, particularly European and American manufacturers occupy the absolutely dominant position in the field of RF and analog IC, but also gross margin areas with the highest average gross margin of between 30% and 40% gross profit margin of some of the analog IC up 70%. "the industry veteran who requested anonymity said.ZHOU Yan Wu said that the field of passive components and the structure is dominated by Taiwan and Japan, the Japanese swept the high-end products, China Taiwan is responsible for the low-end products, functional components, in addition to AAC company unique, is also basically the Japanese. South Korea and Taiwan, China division.Decline in profits"Too harsh industrial environment, intense competition and a direct result of the serious decline in profits." The Macat photoelectric (hereinafter referred to as "Macat") CEO Lee Lap-sun disclosed.Last year the previous year's domestic mobile phone collective big defeat, to further suppress the profit margin of mobile phone parts, so that the Macat this part of the business in serious difficulties. However, in the first half of 2004, Macat business income of 2.6 billion, only a cell phone camera projects a net profit of more than 2600 million.The Macat the phenomenon is not unique.In Shenzhen, Dongguan had a factory do a lot of mobile phone shell, the last two years reduced to a "black phones" tool to join the better quality units committed to the brand's domestic mobile phone manufacturers aware of the importance of quality owned and joint-venture factory.Real local Chinese companies to do the cell phone case, but not much of a certain size. "The the TSD mold workshop supervisor Yu Yabing disclose, TSD has three production plants, plastic mold, injection silk screen with all the production of mobile phone shell conditions. Currently producing 500,000 to 600,000 units a month cell phone case, most of supply Telsda phone.If a mobile phone output reached 300,000, while the price of mobile phone shell accounts for only about 1 yuan, if it is 500,000, the price will drop to about 0.5 yuan. "First Financial Daily" learned from multiple sources, in addition to semiconductor components, the profits of the vast majority of mobile phone parts has become a low-profit, gross margin below 10%."Our gross profit margin of around 5%." Yang Lin said of the resistor-capacitor the Xianghai company responsible person of the major suppliers for mobile phones, even to the level of resistance and capacitance, mainland manufacturers of quality is still slightly inferior to overseas manufacturers.New HopeHowever, this does not explain the bleak future of the mainland's local enterprises in the mobile phone upstream components, new hope is on the rise."Our cell phone batteries has been done in China NO.1 supplier of Nokia, Motorola, Samsung and other international brands." BYD (1211.HK) President's Office main Renwang Zhen said that success in business development, "kangaroo effective copy from the initial nickel-chromium batteries, nickel-metal hydride battery, lithium ion battery, and then expanded to the mobile phone parts. The so-called "kangaroo effective replication" refers to each new business is feeding out in front of the sterile bag.BYD battery from the phone successfully cut to the phone component manufacturing, mainly based on the accumulation of the original technology and customer BYD production of mobile phone components including LCD modules, plastic shell, keyboard, flexible circuit board, camera, vibration motor such as Nokia, Motorola, Samsung, Kyocera, Bird, Lenovo and other mobile phone brand suppliers.BYD mid-2006 performance reports indicate that as of June 30, 2006, operating income reached 5.683 billion yuan, including battery revenue of 1.922 billion yuan (33.8%), mobile phone parts revenue of 2.104 billion yuan (37%), Automotive revenue of 1.656 billion yuan (29.2 percent), mobile phone parts has become BYD business first business for the first time beyond the main business of its battery.

Three course through the development of the printing machinery

World Printing Machinery has made great development since the 1980s. In 20 years, the development of the printing machine has gone through three stages.The first stage is the beginning of the 1980s to the early 1990s, this stage is the heyday of the offset printing process development, a large number of offset printing machinery manufacturers worldwide supremacy. Known are: Germany, Heidelberg, MAN Roland, KBA, Miller (Miller), the former East Germany's Planeta (Planeta), Bo Lv Graf (Polygraph), Japan Komori, Hamada, Akiyama, Mitsubishi Heavy Industries, Arizona (in Solna, Sweden), Italy the Ou Musuo (OMSCA), Nebbiolo (Nebiolo), the United States, Harris (HARRIS) and so on. This period of sheetfed offset printing speed of 10 000 printed / hour. A four-color printing presses, pre-adjustment time is generally about two hours. Press automatic control is mainly focused on the automatic knot paper, auto paper, auto cleaning, ink automatically detects the amount of ink automatically adjust and remote registration. This period, in addition to monochrome, two-color machine, sheetfed offset press manufacturer almost all four-color machine manufacturing capacity, most manufacturers are able to manufacture paper tilting mechanism, two-sided printing.The second stage is the beginning of the 1990s to the late 20th century. Into the 1990s, a sheetfed offset press as a symbol, design and manufacture of printing machinery in the international level a big step forward. Germany, Heidelberg, MAN Roland, KBA and Komori of Japan, have introduced their respective next-generation representative of models. Compared with the first stage of the model, the speed of a new generation of models to further improve, 10000 India / hour to 15,000 printed / hour, pre-press pre-adjust the time by about two hours of the first phase of the greatly shortened to 15 minutes or so. The level of automation and production efficiency of the machines has greatly improved.Printing machinery into the 21st century ushered in the third stage of development. Currently, sheetfed offset some models can reach 17000-18000 printed / hour, but the manufacturers do not aggressively pursue the maximum printing speed of printing presses to improve, but through the application of IT to further shorten makeready time pursuit of higher productivity and the replacement of live time.Become the focus of development in the printing machinery automation, network, production integrated, digital workflow and management information systems (MIS) of the link. Heidelberg CP2000 automatic control system in addition to the whole machine to the paper, feed and guide the paper, ink, water, version, registration, cleaning, drying, glazing coating, dusting and received certificates of compliance and each aspects of the work is preset, control and fault diagnosis, but also printing companies all production process network, online transmission prepress image processing data (CIP3/PPF or CIP4/JDF data). MAN Roland's PECOM system, Komori system DoNet the KBA's OPERA system also has a similar function. The new century, most of the offset press manufacturers have developed the DI digital press. Such as Komori's Lithrone S40D presses (B1 format), Ryobi the the 3404DI press the KBA 74Karat models, the Heidelberg SM74DI type printing press (B2 format) and the fifth generation of Heidelberg fast sit-in Type --- QMDI46-4Pro machines (B3 format). In addition, in order to adapt to the demand for high-end color print, 8 color groups and even group of 10-color multi-color group of two-sided printing, additional on-line finishing functions all kinds of sheet-fed offset press (including a small offset press, DI direct The development trend of the plate-making machines and large offset press), and the technology matured, the type of press has begun to squeeze originally belonged to the part of the web press market.According to the European printing and paper processing machinery manufacturers associations (EUMAPRINT) statistics show that, due to the impact of the global economic downturn, the seven countries, including Germany, France, the United States, Italy, Switzerland and other printing machinery and equipment sales in 2002 decreased compared to 2001 13.08%. From the analysis of economic sentiment index, Europe, America and China, Russia, Japan and other 11 countries, only China, Russia is a rising trend, the rest were dropped, including German sales of approximately $ 6.8 billion in 2002 compared with 2001 declined by 12%; U.S. sales of approximately $ 2.27 billion, decreased by 16% compared to 2001; England's 2002 sales fell 24 percent in 2001, approximately $ 1,064,000,000; Italy fell by 8% approximately $ 763 million. 2001, annual output value of printing machinery and equipment of the top five countries: Germany, $ 7.73 billion, Japan $ 3.918 billion, U.S. $ 2.702 billion, Britain $ 1.4 billion, Italy $ 829 million. Printing machinery and equipment exports before 2001, five countries were: Germany $ 6.325 billion, Japan $ 1.578 billion, U.S. $ 1.246 billion, Italy $ 1.06 billion, Britain $ 940 million. 6 of the 2001 printing machinery and equipment imports: U.S. $ 2.2 billion, China $ 1.3 billion, Germany $ 1.228 billion, Italy $ 922 million, Britain $ 920 million, Japan $ 798 million. Chinese printing machinery market in 2002, spent a single printing machinery and equipment sales increased 13.8% to become the battleground of the world's printing and printing equipment manufacturer.According to the latest statistics of the printing branch of the German Machinery and Equipment Manufacturers Association (VDMA), the 2003 German printing machinery industry output value of about 7 billion euros, lower than in 2002, 13 percent. Which accounted for 4.8 billion euros printing machinery and paper processing machinery accounted for 1.1 billion euros, the rest of the paper production machinery. Printing technology in Germany continued to hold the leading position in the world, its global market share of over 30%, exports up to 80%, mainly exported to the United States, China and the EU member states. German exports to China Printing Machinery in 2003 370 million euros, accounting for 9.8% of the total exports of the German printing machinery, China has become the second largest single export market for German printing machinery. The United States remains the largest importer of German printing machinery, accounting for 1/6 of the total exports of the German printing machinery.

Introducing the WWII codebreaker Alan Turing preserved

Papers associated with codebreaker and pc pioneer Alan Turing will visit a British museum following the National Heritage Funeral Fund stepped into help buy them for that nation.

The government-backed account said Friday this had donated a lot more than 200, 000 lbs ($320, 000) to some campaign to cease the notes as well as scientific papers from likely to a private purchaser.

The fund’s seat, Jenny Abramsky, said the collection will be a permanent memorial in order to "a true battle hero. "

The documents were set up for auction through Christie’s in November but didn’t sell.

An online campaign to maintain them in Great britain raised 28, 500 pounds from members from the public, and pc firm Google led $100, 000.

The papers will navigate to the Bletchley Park Art gallery northwest of Birmingham, which commemorates the actual famous World Battle II codebreaking middle.

One of the actual founders of contemporary computing, Turing proved helpful at Bletchley Recreation area, and helped break Nazi Germany’s solution codes by making the "Turing bombe, inch a forerunner associated with modern computers, to assist reveal the settings for that Nazi’s Enigma device.

Turing also did pioneering focus on artificial intelligence, building the "Turing Test" in order to measure whether the machine can believe. One of probably the most prestigious honors within computing, the $250, 000 Turing Reward, is named following him.

But he wasn’t always considered the national treasure. Turing had been prosecuted for homosexuality, removed of his protection clearance and intentionally treated with woman hormones. He after that killed himself within 1954 at grow older 41.

Homosexuality had been illegal in Great britain until 1967.

Last year, then-Prime Minister Gordon Dark brown made a public apology with respect to the government with regard to Turing’s "inhumane" remedy, saying: "We’re i’m sorry, you deserved a lot better. "

The majority of Bletchley Park’s solution files were destroyed following the war, and Turing remaining few records associated with his work.

The papers with this collection belonged in order to his friend as well as fellow codebreaker Max Newman and can include 16 of the actual 18 scientific documents Turing published within his lifetime — notably "On Computable Amounts, " a landmark within the history of processing.