Published:2011/10/30 22:42:00 Author:Ecco | Keyword: computer motherboard
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Published:2011/10/30 22:43:00 Author:Ecco | Keyword: computer motherboard
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Published:2011/10/24 22:26:00 Author:Ecco | Keyword: computer board
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Published:2011/10/24 22:26:00 Author:Ecco | Keyword: computer board
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Published:2011/10/24 22:27:00 Author:Ecco | Keyword: computer board
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Published:2011/10/31 21:08:00 Author:Ecco | Keyword: computer motherboard
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Published:2011/11/7 18:58:00 Author:Ecco | Keyword: power supply, COMPAQ , multi-frequency monitor
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Published:2011/11/7 19:00:00 Author:Ecco | Keyword: power supply , COMPAQ , VGA , multi-frequency , color display
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Published:2011/11/1 20:44:00 Author:Ecco | Keyword: power supply , color display
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Published:2011/11/1 20:42:00 Author:Ecco | Keyword: power supply , AOC , color display
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Published:2011/11/1 20:46:00 Author:Ecco | Keyword: power supply, AOC , color display
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Published:2011/11/1 20:48:00 Author:Ecco | Keyword: power supply , COMPAQ , VGA, multi-frequency display
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Published:2011/11/1 20:49:00 Author:Ecco | Keyword: power supply , COMPAQ , TTL , color display
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Published:2011/11/1 20:52:00 Author:Ecco | Keyword: power supply , dual-frequency, high-resolution , color display
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Published:2011/11/7 20:50:00 Author:Ecco | Keyword: diode , gate decoding
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Published:2011/11/7 20:46:00 Author:Ecco | Keyword: diode , gate decoding circuit
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Published:2011/11/7 20:51:00 Author:Ecco | Keyword: Dynamic audio preamplifier
This is a 3 stage discrete amplifier with gain control. Alternative transistors such as BC109C, BC548, BC549, BC549C may be used with little change in performance. The first stage built around Q1 operates in common base configuration. This is unusuable in audio stages, but in this case, it allows Q1 to operate at low noise levels and improves overall signal to noise ratio. Q2 and Q3 form a direct coupled amplifier, similar to my earlier mic preamp.Input and Output Impedance:As the signal from a dynamic microphone is low typically much less than 10mV, then there is little to be gained by setting the collector voltage voltage of Q1 to half the supply voltage. In power amplifiers, biasing to half the supply voltage allows for maximum voltage swing, and highest overload margin, but where input levels are low, any value in the linear part of the operating characteristics will suffice. Here Q1 operates with a collector voltage of 2.4V and a low collector current of around 200uA. This low collector current ensures low noise performance and also raises the input impedance of the stage to around 400 ohms. This is a good match for any dynamic microphone having an impedances between 200 and 600 ohms. (View)
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Published:2011/11/7 20:53:00 Author:Ecco | Keyword: amplifier circuit
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Published:2011/11/7 20:34:00 Author:Ecco | Keyword: Two , alternating flashing , LED light , digital IC
The chart shows the TTL or CMOS digital integrated circuits controlling circuit, and it uses the transistor to drive two LED lights flashing alternately. Different supply voltage can be used to change the R's value and the VD3 regulation to meet the alternately flashing requirements.
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Published:2011/11/7 20:35:00 Author:Ecco | Keyword: flashing LED , digital IC
Digital integrated circuits can be TTL or CMOS circuits , and VT uses the general NPN low power tube.
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