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  1. Externet

    Gain of operational amplifier...

    Hi. Is the gain in this case, Rf/Ri = R1/R2 = 10K/100 = 100. Is that correct ? The coil itself has 1000Ω DC resistance. Is the gain still 100 or is it Rf/Ri = 10K/ 1100 = 9 ? If R2 is substituted by 0Ω, the coil being 1KΩ. What is the gain ? The point is if the coil can be considered as a {0Ω...
  2. Externet

    Analog USB... yeeeeeah !

    Hi. Opened a tiny speaker amplifier from China and found the audio inputs connected also to a mini USB receptacle traces. The analog USB has born ! ;) [ The brown wires are output to speaker. There is a 3.7V cell under the board. IC is 8002B ]
  3. Externet

    1W audio power amplifier driven by electret ?

    Is there such thing among the multitude of tiny ICs new in the market ? Am after finding, ideally : Integrated circuit, Analog amplifier , any class, BTL or not, For a 3 to 4 V DC supply, 1W or near that power output, For electret microphone input, or conventional 8Ω cone speaker as microphone...
  4. Externet

    How would you make a 120VAC powered beep/chime ?

    Hi. For an elderly person that forgets to turn off the electric stove; I would like to add inside the control panel, a periodic beep once a minute as a reminder when a 'burner' is on. Without adding a low voltage power supply, tapping from the neon 'ON' indicators, when energized, something...
  5. Externet

    In search of a brain...

    My last brain transplant did not go well. They gave me a refurbished one. Not recommended... Am looking for a mechanism assembly that will release a string across a 3mm plastic wall. An actuator inside a hermetic sealed 'bottle'; the mechanism outside holding/releasing the string. -NO...
  6. Externet

    Cell phone accepting external video ?

    Hi. Anyone knows how to display a video signal on a cell phone screen in real time ? Point is to see a surveillance camera with sort of virtual reality goggles, NO internet involved, no video coming trough the air, just wiring-in a composite signal. In other words, using the phone as a monitor.
  7. Externet

    Virtual goggles...

    Never tried them. Seems are meant to insert a smart phone in them to view its screen, perhaps with some application running. Does such application splits the screen into two images to allow binocular vision ? If a compact monitor or television could fit in them; would the screen be viewable ...
  8. Externet

    Electromagnetic emission...

    Hi all. - A magnet produces a magnetic field that can be detected by a proper instrument, perhaps 1 metre away if powerful enough; Yes or no ? - If that magnet has a coil wound on it, and that coil is fed with AC, its field becomes magnetic + electromagnetic, and can be detected by the proper...
  9. Externet

    Looking for a consumer integrated circuit...

    Once upon a time, a plain old stereo receiver had a tuning 'aid' made of three LEDs in the shape of |> 0 <| The red triangular outer LEDs showed off tune. The green central LED showed when a radio station was properly tuned. The LEDs were driven by a simple consumer IC. What ICs that you...
  10. Externet

    Can you identify this 14-pin IC in tone detector circuit from the schematic?

    Hi am looking for a similar functionality of a CD4046 IC but in 14 pins. Any family as CAxxx, CDxxx, MCxxx or else. Do you have suggestions ? This is a very, very difficult question but gave up on other means to locate/search such probable chip. It is for a proven good working...
  11. Externet

    New LEDs from 0.8V !

    Periodically I receive information about new products directly from manufacturers. The latest one are LED 'bulbs' that run from 0.8V to 1.8. Yes, white too. :eek: At the end of list, Part number starts with OBD3 : ----> http://www.optosupply.com/EN/product_list2.asp?sid=121&bid=158&i=2&pdid=2&...
  12. Externet

    Wanted: CD22204 or MC145436 ICs

    If someone has these to sell/trade, please let me know; and what you may want. Am in USA. Thanks.
  13. Externet

    Chi Mei LCD panel inside TV

    Hi. Feels painful to dump it; found a couple of smoked parts -Coil and transistor in a DC-DC upconverter circuit.- Of course they blew up to protect its surface mount fuse nearby on the display panel board (Not the receiver main board) I know the DC-DC chip takes 5.1V input and upconverts to...
  14. Externet

    Waveform signal inversion...

    Hi all. I would appreciate suggestions to invert an existing sawtooth signal /|/|/|/|/|/|/|/ onto a \|\|\|\|\|\|\|\ Preferably with the use of a common emitter transistor circuit Note no amplification (gain) is desired Note the sawtooth signals are 18 Vpp riding on DC The bottom...
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