Life-Sized OP-AMP!? - How do OP-AMPs work? 

Thanks for watching!

Performing mathematical operations - hence "operational" amplifier. The discrete one didn't arrive for many more years the 709 was the first big one I think. I did a version of the Jensen 990 which is a good deal more complicated but functionally identical. Now people probably mock the 2n3904/6 as being old. But get this, at 100 uA of collector current they are the cheapest very low noise transistor out there. Of course, this means the next stage has to do some serious work but with additions like a current mirror and a constant current sink in the tail and that thing's performance is out of this world. I suspect paralleling a few up would make things better, although I've used a MAT02 in my design for the ultimate front end.

That would be a great comparison!

should be quite horrendous even with high tolerance resistors and hand selecting the transistor pair. Could be a lot more stable thermally just by using a couple of TO-220 bolt together for the differential circuit but clearly outperformed by any jellybean IC.

Yeah i a wondering this too. I think the lowest signal that can be amplified would be 0.6 V because that's the threshold for transistor to turn on?

Glad you enjoyed it!

Thank you!

Glad to hear that!

Good idea :)

That's the compensation capacitor and it stabilizes the op-amp. Without it, the the op-amp oscillates. So, the capacitor is there to dampen those oscillations.

This circuit assumes that you are starting with a single power source which you measure from 0 to VCC. Connect your ground to VEE. The output of the circuit is now your 'virtual ground'. In order to get a negative voltage, you need to measure from the virtual ground to VEE. Falstad has a voltmeter which you can use for this purpose. Connect the negative end of the voltmeter to the virtual ground and the positive end to VEE. I hope that this helps!

@@SineLab Ok, thanks!!