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  1. K

    [b]Questions regarding Switched-Mode Power Supply[/b]

    Also, power supplies that are not integrated into a single product are somewhat general purpose. Whether they waste too much power is not as important as their purpose.
  2. K

    MOSFET VGS

    So there isn't really much difference between using a MOSFET and a bipolar transistor. That is what I expected, however a good design needs to utilize one or the other based on component charateristics and circuit requirements.
  3. K

    Multiple base/emitter transistors

    A biploar transistor OR gate uses an input transistor with two emiiters. I have never seen these used elsewhere and am surprised to see it used for OR gate design. Are unusual devices not seen so much because of cost, availability, or design difficulty?
  4. K

    powering on and off

    Designing circuits for reliability is different than designing circuits for performance. But your saying that all it takes is staying within component specification. If I need to power a 100W load, then it's fine to use a device that's rated to deliver 105W?
  5. K

    powering on and off

    When building a circuit from initial design, a lot of components fail prematurely. Is it due to electrically stressing the components temporarily, or powering the circuit on and off? Most commercially bought products are rigorously tested, but I have some simply designed circuits that would...
  6. K

    [b]Questions regarding Switched-Mode Power Supply[/b]

    Indulis, do commercial power supplies utilize switch mode? Most operate directly from the power outlet, and even the cheapest AC to DC adaptors are used to power laptop computers.
  7. K

    MOSFET VGS

    Saturated biploar transistors do have a lot of base current, but the power dissipation is the same as a MOSFET. A bipolar transistor can be put into cutoff or saturation by 1V. A MOSFET reguires a high VGS difference between saturation and cutoff, maybe 5V. But I know that biploar transistors...
  8. K

    MOSFET VGS

    MOSFETS tend to have a high VGS requirement. I see them used a lot in power supplies. But the real benefits in using a MOSFET over a biploar junction transistor, although not immediately noticeable from a schematic, don't appear to be utilized. Might it be better not to use MOSFETS at all? Or...
  9. K

    Pi filter for impedance matching

    I'm surpised at the results. I know that mismatching impedances can cause standing waves, and it may depend on where you probe on the transmission line. But I think there would still be enough signal loss, and it would seem hard to get that good of a measurement to make a comparison.
  10. K

    Pi filter for impedance matching

    A pi filter can be used to match loads? Most impedance matching that I've seen match the source and load impedance. Although depending on the application, pi filters can play a role in impedance matching.
  11. K

    MOSFETS in parallel

    That transistor is also used to create the DC bias for the MOSFET. To bias the MOSFET with only a 555 timer creates a lower impedance and higher current for the 555 timer. It's common to buffer IC's with higher current transistor's with high current loads, and in this case the load is the MOSFET...
  12. K

    Battery Charging - Help?

    I'm not good with battery technology, but small batteries that are contantly being used might benefit from an intelligent recharging system. Slow charging, I've always heard, is more desireable than fast charging.
  13. K

    555 timer

    Simple circuits such as the 555 IC are still being used. Microprocessors use a variety of simple circuits so as not to introduce unnecessary problems. So why do so many electronics products have so many components?
  14. K

    Re: Ldi/dt of an inductor

    A diode in parallel with an inductor, like many protection diodes, prevents adverse voltages generated from the inductor from shortening the life of the connected devices.
  15. K

    MOSFETS in parallel

    One MOSFET is a better idea. Puting MOSFETS in parallel that all do the same thing only serves one good purpose and might be marginally beneficial. Replacing the transistor with one that is not designed for may work if it's close.
  16. K

    0-30 Vdc Stabilized Power Supply

    My mistake audioguru, I misread the posting.
  17. K

    0-30 Vdc Stabilized Power Supply

    Is it somewhere in between a 0 volt power supply and a 30V power supply? You need to be more specific on the voltage requirements of the circuit. Your talking about designing a very expensive power supply.  I would use a variable voltage regulator for most applications. If you have a general...
  18. K

    transistor emmiter capacitors

    I don't see how the term "negative feedback" can be applied to an emitter resistor. 
  19. K

    transistor emmiter capacitors

    I've seen some circuits that use a capacitor in parallel with an emitter resistor. The RC time constant needs to be short compared to the period of the input, or signal distortion will occur. Is this a real consideration of circuit design, or does it not really matter in most circumstaces?
  20. K

    Voltage detector in need of hysteresis

    You might try using negative feedback instead of positive feedback if you don't need that high of gain. Opamps can latch up and the switch point voltages can be hard to control. Even at a low gain, getting the bias you want is sometimes difficult.
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