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  1. I

    pnp vs npn?

    Yes, I agree 1000% with that! This isn't splitting hairs... if you were taking a test, do you think the Professor would let you slide if you were to answer a question by saying... turning transistors on and off it isn't done with electrons, its done with current... ? Do you think that would be...
  2. I

    pnp vs npn?

    I know exactly what you mean and what your trying to say, but for the benefit of those that are not "well versed"... Current is electrons and resistors don't supply current, they limit current.
  3. I

    pnp vs npn?

    What does mean to you? Remember this from earlier in the thread... This is fact, which in turn means that in one case current is flowing in, and in the other it's flowing out.
  4. I

    pnp vs npn?

    A simplistic way of looking at it is...
  5. I

    pnp vs npn?

    It's all about the transistors function within the circuit. Wait until you start to explore the world of FET's... JFET, MOSFET, n, p, enhancement , depletion...
  6. I

    What are Heat Sinks??

    A correction is needed to my explanation above (thanks to Zeppelin who caught it), heat sinks are rated in degrees C per watt, not he other way around. Heat sink and component surfaces are not perfectly flat or smooth. To maximize surface area contact, you want to fill all those imperfection...
  7. I

    What are Heat Sinks??

    Yeah.......... OK 150 is a bit high. Our work de-rating guide lines call for max junction temp of 130
  8. I

    What are Heat Sinks??

    A "google search" for heat sinks will show you all the different sizes and shapes. Heat sinks are rated in watts/degrees... in other words, a heat sink can dissipate a certain amount of watts and only increase in temperature so may degrees. Say you had a MOSFET with 10 mOhms on resistance. You...
  9. I

    What are Heat Sinks??

    Heat sinks is better lumped into Physics than electronics. Basicaly there are 3 ways to transfer heat, conduction, convection and radiation. The most effective of these is conduction. Metal/s, conducts heat a lot better than air. The magic is in in the amount of surface area exposed to the air...
  10. I

    0-30V PSU - prblem with current limiter

    If he in fact has "voltage regulation", then Q1 can not be on, as it would pull U2's output low, and with U2's output low, there is no output voltage.
  11. I

    LED dimmer

    You might try looking at the data sheets and app's notes for the Linear Tech LT3486 and LT3474 for ideas. They seem to control brightness by voltage not duty cycle directly.
  12. I

    transformers

    Not true... For iron core transformers... The voltage equation is V=4*F*f*a*N*B*10^-8 Where: V is the voltage across the winding F is form factor (1.11 for AC) f is the frequency a is the cross sectional area (cm^2) N is the number of turns B is the flux density (gauss) The power equation...
  13. I

    Another INVERTER we can talk about..

    Did you consider that the MOSFETS run for a long time in their "Ohmic Region" as the cause of them getting hot? Since the current, like the voltage, is a sinusoid, at "crossover", the MOSFET's shouldn't  be conducting any current at all. As a general statment, that's a little misleading to...
  14. I

    Voltage Regulator Question

    John You can get 100uF ceramic cap's nowadays if you can live with a low voltage. 2.2uF caps are a dime-a-dozen and nothing special... check TDK or Murata.
  15. I

    Paralell resistors

    Any number of resistors of the same value in parallel is equal to the resistor value divided by the number of resistors, it's not just limited too 2... i.e. 10, 100ohm resisistors in parallel is 100/10=10ohms... it's one of those things that works out that way given certain conditions. The...
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    Marantz: Please help me find Capacitors!!!???

    Those capacitors are not that hard to fine... the first catalog I took off my bookshelf has those values and voltage ratings (Cornell Dubilier), but most importantly, what is the case size?? CD# 4700
  17. I

    0-30 Vdc Stabilized Power Supply

    Prior to the current limit threshold, U3 is "acting" like a comparator, sitting at the positive rail waiting for the voltage across R7 to increase. Unless someone wanted to use the supply as a "regulated current source" whiles it's in current limit, does current regulation matter?? Not that it...
  18. I

    0 ohm resistor

    Actually, wire wound resistors do have inductance. As far a wire, it's about 20nH/inch. Yup... zero ohm jumpers can be/are used for configuring different options. They are also used a as "bridge". When you have to keep cost's down, manufacturers use them to avoid having to go to a double sided...
  19. I

    0-30 Vdc Stabilized Power Supply

    Yes, but not exactly... true, the U2-p3 node voltage doesn't drop quite as fast (.1
  20. I

    help with producing a current waveform

    If you have a triangular waveform already, why not just apply it directly to a resistor? That will give you your triangular current waveform. If you need more power, apply the signal to the resistor with a emitter follower. A triangular waveform is not a pulse. Which do you need? What is a...
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