Discrete OP-Amp

342

06:19:35

This is very similar in design to the 741 op-amp, and was in fact based off of it. With negative feedback it will not oscillate.

published 7 years ago

hurz

7 years ago

741 is quite an old design, but a non inverting amplifier with gain 11 and 1Vpeak input sinwave should give +-11V at output. This one here gives +11.1 and -10.9V which indicates quite a big offset voltage of about 100mV

hurz

7 years ago

Here with an quite high offset compensating series resistor http://everycircuit.com/circuit/4885106815926272

jason9

7 years ago

I see. I was wondering where a resistor could go to counter the offset voltage. It hadn’t occurred to me to put it in series with the input.

hurz

7 years ago

Actually its the balance of the input differential amp. BJTs needs current and current does drop voltage 😁

jason9

7 years ago

If I remember correctly the 741 actually had two pins dedicated to being used in conjunction with an external potentiometer to correct offset voltage caused by manufacturing tolerances, so that could be implemented here.

deadall127

7 years ago

You are right

deadall127

7 years ago

Here's my usecase of the 741 if you want http://everycircuit.com/circuit/6696519252049920

hurz

7 years ago

Yes, to algin the chip tolerances, the external poti is used. But your design must also take it into account, so dont forget to drop an equal amount of voltage on both inputs. Thats something the offset compensation by external pot is not made for!

BillyT

7 years ago

👍

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