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Simple Op Amps questions

  1. Jun 17, 2006 #1
    ok, can someone explain these two circuits?

    should be pretty simple, but i can't seem to do it right... the book im learning from doesn't have the full solution, so i have to guess what's wrong with my calcs, and i don't think it'd be a good idea to learn like this to my exam...

    i'll explain what i did:
    for the second one with the V_ref on both sides:
    the v_out due to V_in and V_ref i'd get [tex]\frac{(V_{in}+V_{ref})R_F}{R_G}[/tex]
    and due to the other V_ref i'd get [tex]\frac{-V_{ref}R_F}{R_G+R_F}\frac{R_F}{R_G}=V_out-\frac{-V_{ref}R_F}{R_G+R_F}[/tex]
    because [tex]\frac{V_{ref}R_F}{R_G+R_F}[/tex] is the voltage of the entrance to the Amp, so the current would be [tex]\frac{-V_Amp}{R_G}[/tex] and so the voltage in V_out would be... oops, now that i explained what i did i found the problem.... i thought the voltage in the Amp is zero, but it isn't for the second time...
    no i add them and it's fine

    i'll write in a bit what i did for the other circuit... i nust run...

    you can just ignore this whole silly post... i found my error, just needed to go out with my friends and see a stupid movie to clear my head, i feel like so stupid i got stuck with such a simple circuit for so long...

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    Last edited: Jun 17, 2006
  2. jcsd
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