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  1. autir

    bjt / jfet / mosfet as input in audio amplifier

    Hello all. I am trying to design a low power guitar amplifier using only BJTs. Since the output impedance of a guitar is high, I was thinking of using a jfet instead of a bjt as the first stage. The problem is, I have no experience with fets and I do not know what to use. I have read in several...
  2. autir

    555 with unconnected trigger

    Hello all. I have built a simple circuit with a 555 as a monostable multivibrator on my breadboard. The circuit is the one documented in TI's 555 datasheet. The output goes to a 0-999 counter (three 7447s and three 7490s ICs). The 0-999 counter is a seperate circuit built on stripboard and works...
  3. autir

    logic family selection

    Hello all. Recently I discovered that the TTL ICs praised in my books are in reality power hungry, ancient technologies - even the LS variant I have used to make some simple circuits. I would like you to propose an alternate logic family. I would like the following characteristics: DIP package...
  4. autir

    NiMH Charging

    I have read a few articles regarding recharging methods for Ni-based rechargeable batteries (NiCd, NiMH). I have a few questions about the simple constant current method, that is without timers, dV/dt or dT/dt detectors, or anything else. 1) What do you think of the figures given here...
  5. autir

    7447, 7448 decoders

    Hi all. I have downloaded TI's datasheet about the 7446-7449 family of BCD to 7-segment display decoders. (http://focus.ti.com/docs/prod/folders/print/sn7447a.html) 1) The '46 and '47 decoders claim to "drive indicators directly", while the '48 decoder claims that "internal pull-ups eliminate...
  6. autir

    suitable fuse for digital multimeter

    Hello all. I have blown the fuses of my two "el cheapo" digital multimeters. What should I replace them with? Slow-blow or fast-blow?
  7. autir

    BJT biasing formulas

    Hello all. For the past few months (ok, it was not my sole occupation
  8. autir

    Time division duplex led

    Hello all
  9. autir

    Choice of op.amp. model

    Hello
  10. autir

    Impedance matching

    I am trying to design a class-A audio preamplifier. The very classic design we all know, with 1 transistor, 4 resistors and 3 capacitors. Should the ideal input impedance be of equal value to the output impedance of the previous stage (e.g. electret microphone)? Should the ideal output impedance...
  11. autir

    Need e-shop located in EU

    Hi all I have been searching for electronics' e-shops situated in the European Union for some time - but haven't found anything. By the term "EU" I am referring to the no-toll-tax zone of countries (I am uncertain whether GB is part of the show). Does anyone have something to suggest? Thanks a...
  12. autir

    Op.Amp. vs. Diff.Amp.

    What are the differences between an operational and a differential amplifier?
  13. autir

    Choice of small signal BJTs

    Hello ppl
  14. autir

    Choice of switching regulator IC

    Hello all  :) I have decided that the new project I want to build ( a 1.2-30V, 3Amp variable PSU) should have a switching regulator IC instead of a linear one. After a search I have decided that National's LM2576T-ADJ is an IC well-suited for my needs. Does anyone have to propose a different...
  15. autir

    Stripboard + Acetone

    After reading some articles here regarding cleaning stripboards and PCBs after the soldering process, I went to a nearby paints store and asked for isopropyl alcohol or acetone. They only had acetone, of which the smallest container was a 1-liter metal vial. I bought one for 2.60 Euros. When I...
  16. autir

    Opinion on a brand of solder wire

    What is no-clear, rosin-based etc. flux? Are there types of flux which are corrosive and must be avoided at all costs? If so, why are they in production? What should we pay attention to when buying solder wire? Ok, here goes a specialised question
  17. autir

    "Line In" requirements

    In a "typical" (if such a thing exists) Line-in interface -> What is the input impedance ? -> What is the Vp-p(max) ? -> Do PC Soundcards' specifications differ? Thank you.
  18. autir

    Electret microphones characteristics

    Quoting from http://www.epanorama.net/circuits/microphone_powering.html: -> How exactly is Zout calculated? -> What is the internal Z of a typical electret capsule? -> What is a typical Vp-p value produced from such a circuit? Thank you.
  19. autir

    Stripboard CAD

    Hello Does anyone know of any programs which take a circuit and transfer it to stripboard? The only two programs I know exist are Stripboard Designer and Stripboard Magic. The first one I have not tried, but people say it is way inferior to Stripboard Magic, which is impossible to locate. Any...
  20. autir

    PC speakers amp with TEA2025

    The speakers of my PC started to act strangely, and I thought that the time had come to redo some solderings. I opened the speaker containing the amplifier and saw the circuit. It is based on the TEA2025 from ST. I desoldered all components and I'm about to rebuild the circuit on a new board...
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