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elix

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Everything posted by elix

  1. is clamper another word for thermal switch? never heard of it before.
  2. elix

    transistor off

    :D even though it works perfectly in the sim i have to make something of my own creation, else i'm not learning so i'm going to try it now with a active current sink since i can use the gate voltage swing to my advantage. you've won this round *shakes fist* ;D
  3. elix

    transistor off

    i'll try and figure out a way to lower the impendance. some heat wasted is ok, i only need 1 watt from each channel and the mosfet bias will come from the op-amp. question: to lower the impendance don't i have to raise the current or can it be done a simple circuit, i'm trying to keep a class a single ended mosfet. (gotta learn :P)
  4. elix

    transistor off

    is this output stage ok?
  5. elix

    transistor off

    i am starting over ;D btw that current source was working right then i pulled a resistor live and now i have two holes in my breadboard and two cracked fets :-[ good thing i have more :)
  6. elix

    transistor off

    your right, i have it hooked up right on the board but wrong in the schematic, funny thing it works fine in the sim then when i put it right i got a jagged wave!!! so i got rid of the 317 and put a more flexable current regulator in, tell me what you think. still have to build this one but i must go to bed.
  7. elix

    transistor off

    here are the node voltages, i have a vom hooked up to the bottom of r8 and the voltage is hardly moving but something is giving me crazy bass from this regge song, sounds great! 6 ohm load, r1 is 4 ohms, have on a small lead acid battery. i had it as shown and worked great. clean sine waves to 5Mhz, no artifacts to 15Mhz which is the max i can test to. the more current i have the less voltage swing i need?
  8. elix

    transistor off

    "Your OP37A opamp has a voltage gain of 19k/10k= 1.9 with a low impedance source, and a voltage gain of 19k/(4.7k + 10k)= 1.3 without an input. But the OP37A opamp is de-compensated and is unstable with a voltage gain of less than 5. It will oscillate." does it matter since i'm not using a split supply?
  9. elix

    transistor off

    i've made some changes again, the amp did oscillate but because the mosfet was actting as an anttena in the low Mhz. new mosfet, some changes. so far no problems from the op-amp, will look at the data sheet.
  10. elix

    transistor off

    it's not really supposed to have voltage gain, it's a current amp :) rev1.1: the op-amp is opa37
  11. elix

    transistor off

    i'll be making some changes, keep the comments comming. :D
  12. elix

    transistor off

    URL=http://imageshack.us] not bad considering i used whatever was laying around, tell me how i can improve it, spacificly how can i get the mosfet in the feedback loop?
  13. on the data sheet it says you can make a current regulator by just putting a resistor on the adj and out pins 1.25/R = current out, why is it pulling 1.5A with a 100 ohm resistor?
  14. maybe back emf is destroying your regulators?
  15. elix

    transistor off

    thanks audioguru, i'll now proccede to made an amp.
  16. elix

    transistor off

    "IRFZ44 has a minimum drain current of 31A if its gate voltage is 10V" so does it matter what the drain voltage is?
  17. elix

    transistor off

    i'll answer one, Vt is the voltage threshold, should be 0 to start off with but if you reverse bias the gate current flows backwards through it :o
  18. elix

    transistor off

    using split supplys if i keep the gate at 4 volts above drain it saturates, when gate equals 0~4 volts above drain it stays in linear mode (corresponds to Vgs for irfz44, which is what i'm testing). Id=2k[{(Vgs-Vt)Vds-Vds^2}/2] is how you calculate drain current in linear mode but here's my questions: Vt should be what? is Vds the drop between drain and source? it shows up as one diode drop if so. how do you figure out what k is?
  19. elix

    transistor off

    gate V to I is almost 1:1, so what is G used for?
  20. elix

    transistor off

    ok i have 3 points gate voltage current gain Vd 4.6 2ma 1.8 5.2 13ma 2.2 5.6 25ma 2.45
  21. elix

    transistor off

    ok, i think i understand mosfets when they are in saturation mode but i'm having trouble figuring how to calculate gate voltage (Vgs) to drain current (Id) using G(transconductance ratio). in the schematic i just left generic values, i have a led in the place of r2 and i'm making a plot, but for now this is good enough, bed time ;)
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