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Everything posted by indulis

  1. I was thinking I should have asked that no one give him any hints or the answer
  2. KevinIV, where do you get this stuff ... do you just make it up as you go along??? Get a good electronics book, read it, study it and get a good grasp of the fundamentals. You "claim" you "... extend the bandwidth of an opamp by reducing gain". Now ponder the difference between extending the "usable bandwidth" of your circuit by reducing the gain and the op-amps actual bandwidth. I know I shouldn't ask, but will... do you think you have changed the opamps bandwith from what it was with reduced gain??
  3. Reverse current and reverse recovery current are not the same thing. Ultra-fast and fast recovery diodes have a much longer Trr time (hence a higher reverse recovery current) when compared to Schottky
  4. Don't forget the inductance of the wiring.
  5. If the linear amp is for his ham radio, I'm surprised it only needs 13.8V. As for a 100A 13.8V (1.38KW) linear power supply... while it could be done, it's not very practical. The transformer alone must be as big as a boat anchor and weigh just as much, whereas a 1 KW switching supply power supply isn't much larger than a bench DVM.
  6. Go to http://www.ti.com/ and look up UC3906, application notes U-131 & U-104.
  7. Might be General Semiconductor (www.gensemi.com)
  8. Sorry, but I have to ask.... KevinIV, do you have any formal electronics schooling? Do you work in the industry or is your intrest as a hobby? Google "SoC" (system on a chip) that is a good example as to "how complicated they can be".
  9. Power is power... it's not a question of the generator, but rather "the wind". For example (silly perhaps), in a hurricane you could
  10. How much power is going to be dissipated buy the power supply? What
  11. Only in a ZCS or ZVS supply... the other topologies don't have that luxury. In terms of SMPS, the number one thing to get a good understanding of is the concept of Pulse Width Modulation (PWM)... a concept you might want to include in the "Technical Articles" that pertain to DC-DC's on your website. With a solid basic supply design, things like switching losses, parasitic resistance & inductance are really considered higher order effects. Those two components are basic to any SMPS design... the design dictates their value, you don't just arbitrarily "pick" them... be it a simple buck converter, or a more complicated isolated topology. Certainly, good layout practices should be followed to minimize the "loop areas" in the feedback and minimize any proximity effects. As for the "high current paths", short and fat is always preferred.
  12. That is not correct. Inductors have resistance (the wire itself) and capacitors have ESR both of which will and do dissipate power (heat).
  13. You could try windshield wiper motors.
  14. Not true... I use small MOSFET's (Vishay) that have a Vgs of 1.2V... I wouldn't consider that high. No... re-read and UNDERSTAND what Hero999 just said!!!!! If you are really serious when you say that, I'd recommend you get yourself a good book on semiconductor physics read that, then read-up on BJT's, JFET's and MOSFET's... after you have done that, let us know if you still think there isn't really much difference.
  15. The power density of switchers is quite high... for example my (work) bench supplies are Xantrex a XHR 100- 10 (100V @ 10A) and a XHR 40 25 (40V @ 25A). Both are 1 KW supplies and measure ~3"x8.5"x16". In a linear supply of the same power, the transformer would probably bigger than that by itself. Although, one problem that I have run into on occasion is powering a SMPS with a SMPS... nasty things can start to happen, particularly if some noise gets in to the sense lines.
  16. This is a "second order" circuit. You took a bode plot over a frequency range. Things are going to change over frequency. Have you solved the differential equation for this circuit to find the poles and zeros? It's also what is called a "passive circuit"... so, unless you hit a resonant frequency (as AG pointed out) in your sweep, this thing can only attenuate.
  17. That transistor has absolutely nothing to do with the biasing of the MOSFET!!! If you take it out of the circuit, the MOSFET is still "biased" on. It's sole purpose is to turn the MOSFET off. You could run the MOSFET directly from the 555... the problem is that the 555 doesn't have the current driving capability to switch it fast. Anytime you have a MOSFET switching a high current load, you have to switch it fast to minimize "switching losses"... that's the I
  18. You said you had a supply rated at: You said your load is only 200mA. Your supply is more than adequate for your load.
  19. YES!!! Put the gate resistor in the collector of the NPN not to "over-drive" the MOSFET and the PNP will be able to turn it off faster. Most of our designs have PWM's capable of 1 or 2 amp's and if they don't, a driver is used.
  20. With the values shown, it could switch at up to ~48KHz... your not going to drive that MOSFET with a 555 directly at that frequency. A 555 can only sink ~200mA whereas the 2N2222 is good for 1A. Yes, exactly what I said in my original reply.
  21. The 2N2222 can sink a lot more current than the 555, so the "turn off" will be faster... and thats a good thing. I'd even put a diode across the 10 ohm gate resistor to speed it up even more.
  22. The 2N2222 is there to turn the MOSFET off. The 2N3055 gain is low. The 330 ohm will "slow down" the MOSFET turn-on. Why 4 MOSFETS in parallel? The IRF510 is a 100V 5.6A device with an Rds on of .54 ohms. You will need a snubber across the primary winding or MOSFET (maybe both). You show a 3A source... what do you think 4 MOSFET's will do for you besides lower "Rds on"? Better devices are out there.
  23. Or soldering a copper braid (i.e. Solder Wick) on top of the trace.
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