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  1. KrisBlueNZ

    PCBweb Software?

    Does it run within the browser?
  2. KrisBlueNZ

    OP AMP output calculation

    I don't think there's any point asking that question, because you have specified the actual voltages on the op-amp's inputs. An op-amp's output is equal to the differential input voltage multiplied by its open loop voltage gain, which is typically around 105~107. So a differential input voltage...
  3. KrisBlueNZ

    Creating my own transformer

    The bobbin is the plastic part that you wind the wire around. You can't really wind it directly on the core (unless you use a ring core). What do you want to make with it? Some kind of high-voltage source? A high-voltage DC supply? If so, a ferrite core operating in the 30~200 kHz range is...
  4. KrisBlueNZ

    lm317 sub?

    Yes, sorry. I meant the feedback transistor. Those circuits are from: http://www.diodes.com/_files/products_appnote_pdfs/zetex/an62.pdf http://www.taiwansemi.com/DSfile/TS432_D14.pdf
  5. KrisBlueNZ

    Creating my own transformer

    You will also need a bobbin. What frequency will it be operated at? If it's for mains frequency, I doubt you can buy cores and bobbins. I could be wrong. But it might be simplest to find a suitable looking transformer and unwind it.
  6. KrisBlueNZ

    lm317 sub?

    Yes, you can use a shunt regulator like a TL431LV instead of a transistor for Q2. The ON Semiconductor CAT-102 looks like a good option: http://www.digikey.com/product-detail/en/CAT102TDI-GT3/CAT102TDI-GT3OSCT-ND/3487509 It's USD 1.23 for 1-up and has a reference voltage of 0.6V, reasonably...
  7. KrisBlueNZ

    Using all four amplifiers in an LM324

    Also, if you're not tightly budget-constrained, Linear Technology and Maxim. And Texas Instruments too. But I agree that Microchip is a great place to start.
  8. KrisBlueNZ

    Hello.

    Hi there and welcome to Electronics Point :-) It's nice to see someone using their real face for their avatar! What is your interest in electronics?
  9. KrisBlueNZ

    decoder for 8051

    I don't see any question in that post, and I don't know the purpose of it. That doesn't really make sense. What are the 4-bit bit number for? What is the data for? If you're transferring data between two registers, or between a register and memory, there is no need to have any data field in the...
  10. KrisBlueNZ

    help eliminating oscillation in circuit

    Different from what? I suspect Steve would find it easier to help you if he wasn't trying to hit a moving target...
  11. KrisBlueNZ

    lm317 sub?

    I thought it would be the opposite. The output transistor is generating the heat, but its VBE is not a big factor; it's the VBE of the feedback transistor that determines the output current, and that transistor doesn't dissipate much power. So keeping them thermally separate should improve...
  12. KrisBlueNZ

    Some kind of morse code device

    OK, just in case you still want an external circuit to do this, here's my design. It uses a Rohm BU4S584G2 single-gate CMOS inverter with Schmitt trigger input, a versatile device that can be used to make an oscillator with only one resistor and one capacitor and operates over a wide supply...
  13. KrisBlueNZ

    Learning Electronics, need help with my noob circuit

    I pointed you to that tutorial because it will answer all your questions, including questions you didn't even know you needed to ask, which is even more important. Read it until you understand it, and if you have specific questions that it doesn't answer, then ask them, so Steve can update the...
  14. KrisBlueNZ

    help eliminating oscillation in circuit

    No, it just has a PNP-type input stage. Many op-amps (e.g. LM358, LM324, and many current ones) have input ranges that extend a few hundred mV below the 0V rail. It doesn't have a charge pump, but I'm not saying that it's not oscillating. I couldn't say. I would like to see an exact...
  15. KrisBlueNZ

    MOSFET

    The important parameters in that data sheet are: RDS(on) at VGS = 5V, ID = 27.5A: typically 16 mΩ; maximum 20 mΩ RDS(on) at VGS = 10V, ID = 27.5A: typically 14 mΩ; maximum 18 mΩ So it is clearly intended to be able to be used at 5V VGS voltage; in fact, the improvement in RDS(on) going from...
  16. KrisBlueNZ

    Learning Electronics, need help with my noob circuit

    Hi there and welcome to Electronics Point :) The problem is you don't have enough voltage, not current. Each LED requires a certain amount of voltage across it. This voltage is called the "forward voltage", VF and you can measure this with a multimeter on volts range when the LED is glowing...
  17. KrisBlueNZ

    MOSFET

    Logic level MOSFETs are intended to be used with lower gate drive voltages than standard MOSFETs, and their data sheets specify their typical and maximum RDS(on) at at least two different VGS voltages. Older logic level MOSFETs were designed to be driven from 5V logic and their RDS(on) figures...
  18. KrisBlueNZ

    MOSFET

    Yes that's true, but your MOSFET's data sheet should have a maximum ON-resistance (RDS(on)) specified for the gate-source voltage (VGS) that you will be using. You shouldn't rely on the typical characteristics graph. I was just commenting on the terminology - "saturated" for a MOSFET doesn't...
  19. KrisBlueNZ

    MOSFET

    Whoever wrote that was under the same misapprehension as me :-(
  20. KrisBlueNZ

    MOSFET

    So when I've been saying that you need a high VGS voltage to "saturate" the MOSFET for switching applications, I've been embarrassing myself! Not much new there I suppose. Thanks for the lesson Steve :-)
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