Op-Amp Help

Thread Starter


Joined 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!




Joined 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!

Thread Starter


Joined 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!


Joined Dec 20, 2007
I'm still abit shakey when it comes to mosfets
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.