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  1. BobK

    Op amp calculations for ramps!

    Here it is: Bob
  2. BobK

    LED beyond rated Current

    LEDs are less efficient at higher currents (because the forward voltage goes up). So you will get less than 42% more light by going from 700mA to 1A. Bob
  3. BobK

    What is Vb?

    It is just a label for a node. All Vb's should be connected together. Bob
  4. BobK

    Will this charger work with this battery?

    It certainly looks like it works. I would expect it to take 5 to 6 hours to charge a fully discharged 20AH battery at its max current of 5A. Bob
  5. BobK

    LEDs at the die level

    That chip is .3mm(.0118 in) square! And it has contacts on top and bottom. I don't think you could possibly find a way to use it. What are you trying to build? (I think I know already, a device for doing skin treatments, right?) Edited: too many zeros in my inches. About 1/100 of an...
  6. BobK

    gain bandwidth product / op amps

    1. You don't, you get it from the datasheet. 2. GBP is the product of the gain and the frequency. Say it is 1 MHz. That means you will have unity gain at 1MHz, gain of 10 at 100KHz, gain of 100 at 10KHz etc. 3. Yes. Bob
  7. BobK

    LED Power on Indicator

    Yes, put an LED with appopriate resistor between the wires labelled + and - on your diagram. Bob
  8. BobK

    Help with Tiny Monitor Cube Thingy

    Sorry, your spec is unachievable. Bob
  9. BobK

    idea for creating Touch sensitive wire strip like variable resistor

    Well, there is not much variation in voltage along a copper wire unless it is drawing a LOT of current, so I don't see how. Bob
  10. BobK

    Newbie power questions

    The problem with a buck conveter is that it is supplying the full current during the ON period. The average current will be less than the output current, but the peak current will not. If it switches fast and has a large enough capacitor on the input, it could work though. Bob
  11. BobK

    Improve battery life in LED Chaser

    That would give you maybe 70 or 80mA. The battery still should have lasted longer than that. At 100mA, an Energizer Alkaline 9V is rated for 5 Hours discharging to 4.8V. Bob
  12. BobK

    IGBT on resistance - conduction loss

    Why are you using a 5KHz PWM for a heater? Lower switching frequency = less loss, and a heater is not going to be responding at 5 KHz. Bob
  13. BobK

    Improve battery life in LED Chaser

    I would expect the battery to last maybe 10 hours with that circuit. Perhaps there is a (near) short somewhere. Bob
  14. BobK

    question about RC range

    You will have to disconnect them. Bob
  15. BobK

    Wireless trigger for LEDs and buzzers

    Buy a wireless doorbell. Bob
  16. BobK

    Alternating led flasher 555 timer?

    Huh? From the datasheet: • Output Can Source or Sink 200 mA Bob
  17. BobK

    Low voltage sine wave output

    Great! I look forward to seeing it working. Bob
  18. BobK

    Low voltage sine wave output

    Do you have a scope so we can see the output once you wire it up? Bob
  19. BobK

    Low voltage sine wave output

    Yes, those pots should work for frequency adjust and level adjust. I have had some more thoughts about this circuit. It produces a very nice sine wave in simulation, but I am not so sure about it in the real world, it might clip if the gain of the op amp is too good ad 60 KHz. You might...
  20. BobK

    stupid questions

    Yes, the power input is 230 volts, but that has nothing to do with what I said. If the signal input is 2V p-p and the output is 66 V p-p there must be a voltage gain of 33. But this amplifier has practically no voltage gain as drawn. Put a bypass capacitor on the emitter resistor and it might...
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