Op-Amp Help

Discussion in 'General Electronics Chat' started by dmag0006, Jan 20, 2012.

  1. dmag0006

    Thread Starter New Member

    Dec 8, 2010
    Hi, would anyone kindly explain to me the circuit I uploaded? I need to understand what is the use of the components inside the TL071 circuit... that is which act as a buffer, which act as a current source etc...I labelled most of the components in the circuit so it would be easier to explain and below there's also the link of the original circuit... Hope I was clear enough in the question... many thanks in advance!

  2. w2aew

    Active Member

    Jan 3, 2012

    M3, D2, Q7 form the primary current source reference for the circuit.

    Q4, Q11 and Q12 are current mirrors.

    M1 and M2 form a differential amplifier.

    Q1-Q6 form the active load for the diff amp and buffer.

    Q9 and Q10 for a bias stage for the buffer consisting of Q8 and the unnamed NPN transistor above it.

    Gee - I hope I didn't just do your homework for you!
  3. dmag0006

    Thread Starter New Member

    Dec 8, 2010
    Thanks! No it's not my homework, you just helped me out studying for my exam coming up, I understood the LM741 but I found this abit more complicated as I'm still abit shakey when it comes to mosfets....thanks once again!
  4. Audioguru


    Dec 20, 2007
    The TL071 does not have Mosfets. The input transistors are Jfets (junction field effect transistors).
    Some modern opamps use Mosfets everywhere in their design. They are called Cmos (complementary-mos) because they use both polarities of Mos transistors.
  5. Blofeld

    Active Member

    Feb 21, 2010
    dmag, if you have reached the point where you understand the internals of the 741, but you need more practice to understand other analog ICs, you might be interested in the free "Designing Analog Chips" by Hans Camenzind:


    It contains many schematics of analog ICs (including some with the CMOS transistors that Audioguru has mentioned) with explanations.
  6. Brownout

    Well-Known Member

    Jan 10, 2012
    ^-good find, biofeld. I love a free book!