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  1. 2

    Quick op amp question?

    Hi (*Steve*), Yeah! ... your right.... I see what you mean.... I have a hunch maybe there's a mistake with the brackets !!!! :confused: When I have a chance I will try to do the math that involves "Substitute eqns (5) & (6) into eqn (2)". :eek: and see if its a misplaced bracket !!! I think...
  2. 2

    Quick op amp question?

    Hi (*Steve*), I would start a new thread, but I figured since you and I started on this subject, it would be better if I continue it here. Sorry for bringing up an old subject! So I have been wondering what is the reason why a purely differential op amp that has all the same resistor values...
  3. 2

    What is the curent of a unity gain differential op amp?

    understood! thanks guys
  4. 2

    What is the curent of a unity gain differential op amp?

    Hello (*Steve*), I have a few more questions if I may.... Is this what is typically know as the open loop gain? Is this what they call the closed loop gain.. the one determined by rf/ra... ? thanks!
  5. 2

    What is the curent of a unity gain differential op amp?

    oooops ! yes that's what I meant! Ooooh !!! sorry .... let me reword that: :o "May I say that the output's results is by what the non inverting input sees (which is 3Vdc + 3uv) minus what the inverting input sees (Which is aprox 3vdc) resulting in a very small difference which is...
  6. 2

    What is the curent of a unity gain differential op amp?

    yes that's what I thought also.... Okay, so the inverting input as seen by the op amp is 0volts right? And therefore, since we have unity gain, the output results by what the non inverting input sees (which is 3Vdc) minus what the inverting input sees (Which is 0vdc) resulting in Vout of...
  7. 2

    What is the curent of a unity gain differential op amp?

    Hello, In the following op amp configuration, can someone explain how much current is going through ra and rf? If the ra voltage drop is 0 Vdc, how could there be current going through ra?? :confused: thanks!
  8. 2

    Op amp configuration with 1 resistor ?

    ah!!!! I see now! Thanks KrisBlueNZ, I think u saved me lots of fuses:D 24v
  9. 2

    Op amp configuration with 1 resistor ?

    Hi guys, One last question.... I have a power supply that can generate Dc voltage and Dc current. I read that if I put my voltage supply at max and adjust my current knob, the power supply can actually act as a constant current source. See pic of my power supply in attachment. Now, to...
  10. 2

    Op amp configuration with 1 resistor ?

    okay thanks gorgon!
  11. 2

    Op amp configuration with 1 resistor ?

    understood ! when I have a chance I will try it out. I thank you very much for your assistance .... I really appreciate it. This will be fun to try :) Thanks KrisBlueNZ
  12. 2

    Op amp configuration with 1 resistor ?

    Hello KrisBlueNZ, thank you very much for the explanation. So if i omit the series resistor, I could also use an LM317 to do some tests for this right? thanks
  13. 2

    Op amp configuration with 1 resistor ?

    Humm! I think I understand now! We have to provide a 1 ma current!!! But now, we are back to the typical inverter op amp configuration !!! And so I guess its that or an LM317 so to get a constant current source of 1ma.... Thanks guys, sorry for being slow .... :o:o:o 24v
  14. 2

    Op amp configuration with 1 resistor ?

    I don't know what a current source means. The 1 volt is simply coming from a power supply adjusted to 1Vdc. I don't even know how to build a current source :( This is why I am having so much trouble getting any readings to make sense! :( What do you mean by a serial resistor... is it a...
  15. 2

    Op amp configuration with 1 resistor ?

    Hello guys, This morning I ran some tests and all tests were inconclusive. For example: Current measured at input = 1.5ma (I have 1.5 ma as an input current. How would I get 1ma input ?) Non-Inv input: ground Inv input = 1Vdc Rf = 10K Output = approx: -14.2Vdc and not -10Vdc ...
  16. 2

    Op amp configuration with 1 resistor ?

    wow okay, KrisBlueNZ, when I hey back I will try these experiments ! thanks for your help!
  17. 2

    Op amp configuration with 1 resistor ?

    okay I see thanks everyone for your help 24v
  18. 2

    Op amp configuration with 1 resistor ?

    KrisBlueNZ, As misleading or awkward that circuit is I posted it in the hopes of learning something. But it's nice to know that this is a non common topology in op amps and I thank you for your much appreciated assessment of the circuit. Actually it's a print out I had from a while back which...
  19. 2

    Op amp configuration with 1 resistor ?

    Really huh! Okay so I won't test it. :D thanks
  20. 2

    Op amp configuration with 1 resistor ?

    In the circuit the output is not bashed against the output rail.... my negative rail is -15Vdc and the circuit claims that the output is -10Vdc. I haven't tried this circuit yet as I am away from my test bench until Tuesday But, I know for sure if I remove rf, the the output will be bashed...
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