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power transistor

Invention
People usually put on October 2, 1925 Scotland John Logie Baird ( John Logie Baird ) in London an experiment in" scan television." out the puppet's image as the symbol of the birth of television, he was called" the father of television". However, this view is controversial. Because, also in that year, the Russians Sifu Luo Jin ( Vladimir Zworykin ) in the Westinghouse company ( Westinghouse ) to his boss shows his television system.

Although time is the same, but John Logie Baird ( John Logie Baird ) and Sifu Luo Jin ( Vladimir Zworykin ) television system is vastly different. In history, John Logie Baird ( John Logie Baird ) television system called mechanical television, but Luo Jin 's system is called electronic television. This difference is mainly due to the transmission and reception of the principle of different.

The development of television complex. Almost at the same time there are a lot of people doing the same study. The United States of America RCA1939 TV launched the world's first black and white TV set, to 1953 national TV standards as well as the 1954 launch of the RCA color tv.

Structure
Signal system structure
Television signal system [1] system comprises a common signal channel, audio channel and as the release of final circuit three parts, their main role is to the antenna to receive high-frequency signals ( including the image signal and the sound signal amplifying and processing ),dvb t tuners the final reconstructed image on the screen, and in the recovery of audio speaker.

The high frequency amplifier, a mixer and a local oscillator is composed of three parts. Satellite TV and its role is to select and amplification by an antenna to receive television tuner to high frequency television signal, after mixing processing 38 MHz images of frontal signal and the 31.5 intermediate frequency ( MHz first intermediate frequency ) signal sound surface effect is the formation of image of amplitude-frequency characteristics; pre placed role: amplification signal ( 20 dB amount ), compensated acoustic surface filter on the signal loss; surface filter to achieve high tuner and image on the impedance matching between.

ACC ( automatic gain control ): through the control circuit and high on the gain of the circuit, thereby maintaining the geophone output AGC and ANC video signal voltage amplitude basically ****le; ANC ( automatic noise suppression circuit: reduce external noise ) television signal on television transition effects and interference.

Sweeping system structure 　　Television scanning system including synchronizing circuit, line-scan circuit, field scan electric circuit, teletron and feed circuit. Sweeping system's leading role is causes on teletron's fluorescent screen to form the normal diffraction grating.

The amplitude selection electric circuit use synchronized signal in the entire television signal the scope highest characteristic,dvb t receivers takes the composite synchronizing signal the integrated circuit to be bigger than by far using the field synchronizing signal width the good synchronized signal width the characteristic, separates the field synchronizing signal from the composite synchronizing signal, controls the field scan electric circuit, realizes the television field scan synchronization, integrated circuit's separation way also said that the width separates the AFC electric circuit function is the automatic solid present synchronization.

The principle is takes out the good synchronized signal from the composite synchronizing signal, feeds back the line frequency denticle with this aircraft good output stage to plate the signal to carry on the comparison, then the outlet error control voltage adjusts the line scan the frequency and the phase, solid present television synchronizing circuit. Power circuit structure

　　The television power circuit's function is 220 V alternating voltage which provides the television carries on the live pressure (voltage dropping), then after the rectification, the filter, the constant voltage, obtains conforms to request ****le DC voltage supplies various part of electric circuits. The PC three piece of integrated circuit monochrome set, produces now the television is with the integrated circuit ***embly television. The integrated circuit television has following merit:

　　1st, an integrated circuit, contains tens of thousands of television primary device, may replace one or several unit electric circuit,cable supplier thus reduces the complete machine greatly the part total, causes the installment, the debugging working procedure big simplification, raised the production efficiency.

　　2nd, as a result of the primary device quan***y's reduction, the television complete machine's spot number and the connecting lead also greatly reduced, enhanced the product reliability.

　　3rd, the integrated circuit used the most perfect electric circuit generally in the design, the television box therefore enhanced the television complete machine performance index. Because receives the fabrication technology the influence, at present in the integrated circuit can only the ancient low power transistor, the resistance and the low-power electric capacity (below several hundred PF); The inductance, large capacity parts and so on electric capacity, resistance and high efficiency transistor, need to use the television external connection discrete component generally.