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  1. Arouse1973

    Measuring the inductance of a wirewound resistor

    Hey Chris Had a go and got some good results. Changed my setup a bit. Wound 15 turns of 1mm wire around the resistor (0.33R) and a series connected 200nF. Connected 100nF across resistors and wound up frequency until the signal peaked across resistor. Peaked at 1.5Mhz, this works out to be...
  2. Arouse1973

    Temperature compensating a transistor?

    LOL Kris. I have said this all along on a few posts, don't interchange op-amps and comparators. But know one listened to me as usual :) Having a closer look at the transistor I think it might be in common collector mode as this is the only terminal that is not the input or the output. The...
  3. Arouse1973

    Measuring the inductance of a wirewound resistor

    Hi Chris I had to use a small resistance to simulate otherwise it came up with an error. It's so small it won't have any effect on the circuit. Yes L2 is the unknown inductance. I had to use a tuned circuit because I had no other way to show you. But it will give the same result with an LCR but...
  4. Arouse1973

    Transistors

    Yes I have also wondered why people refer to an inversion as a 180 degree phase shift. As a phase shift by definition involves a shift in time doesn't it?. Adam
  5. Arouse1973

    Transistors

    I am with Harald on this one. I think as he mentioned it is all about which aspect of the circuit your interested in. All BJT transistors have the ability to amplify current don't they. But you don't have to use that feature for voltage amplification. I find It's simpler to think of voltage if...
  6. Arouse1973

    Temperature compensating a transistor?

    Sorry Kris I thought this was just a standard op-amp buffer splitting the supply. I should have looked a bit closer. Adam
  7. Arouse1973

    Temperature compensating a transistor?

    Because the PSRR of the half supply circuit is only 6dB with two equal resistors I personally would keep the 4.7uF as this helps with PSRR. Adam
  8. Arouse1973

    Voltage controlled thru opamp playing up?

    Thanks Kris.
  9. Arouse1973

    Voltage controlled thru opamp playing up?

    What's with all this 1960's way of drawing circuits :) Any values Kris? Cheers Adam
  10. Arouse1973

    Voltage controlled thru opamp playing up?

    Here you go. Might look a bit complex but it's not really. Just a constant current cap charger with peak detector with Vbe cancelation. Pictures show working with 19% and 38% DC. Stable enough to bang straight into A to D if you wanted to. You might have to tweak the components for the desired...
  11. Arouse1973

    Voltage controlled thru opamp playing up?

    Hi Kris I would be interested to see your implementation of the RC network that worked over the entire range. Cheers Adam
  12. Arouse1973

    Measuring the inductance of a wirewound resistor

    Hi Chris Here you go. I tested this and it works but you have to take the coupling coefficient into consideration. I chose 70% and the results were without second inductor in circuit the RF was 500K. With the second inductor(unknown) although I had to put in a value, so I made it the same. Now...
  13. Arouse1973

    Use Of Current Source?

    Yes steve. But the resistance at d.c is not infinate which was my first point. Cheers Adam
  14. Arouse1973

    Capacitor Question

    If you apply nine volts to a capacitor rated at 30 volts you will only get nine volts. From your post it seem you think it might charge to 30 volts. The capacitor has a max voltage of 30 volts. Also the cap value is at its rated voltage. So a 100uf cap rated at 100V will read different at 10...
  15. Arouse1973

    Voltage controlled thru opamp playing up?

    Hi mike Still working on it. Looking at capacitor constant current driver and a peak detector. Got something sort of working. Give me the weekend ish. Adam
  16. Arouse1973

    Use Of Current Source?

    I don't think so, a billion ohms is no where near infinate which is a lot greater than the gate resistance of a mosfet. Its lower for a.c um right ok. If it blocks d.c it block a.c. I didn't realise there was a special a.c current. Adam
  17. Arouse1973

    Use Of Current Source?

    And it does not have infinite input impedance. But it is usually very high. Adam
  18. Arouse1973

    Velocity Factor

    :)
  19. Arouse1973

    Measuring the inductance of a wirewound resistor

    The only other method I can think of that is non intrusive is to wind a coil around the resistor. then short the resistor to create a shorted turn of the inductance. Then measure as normal with the LCR, this result will be the mutual inductance. Then measure the wound inductor and subtract the...
  20. Arouse1973

    Voltage controlled thru opamp playing up?

    The RC time constant for all the 56K resistors and the last 4.7nF is 798us and your off time is 647us. I think that the last capacitor is basically not being given enough time to discharge before the next pulse comes along and tops up the cap. This is giving you a higher average than you expect...
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