Quick Question about Amplifiers

[mzdenkov]

Here i am, cleaning red  nail-polish after night of heavy drinking and wondering about amplifiers.

I know that his method on picture was invented by Toshiba(it was told to me by professor at my uni). But i still don't quite get it.
Look at the schematic on the pic.

How on earth do i(or amplifier, not me  ) model driving this BD power transistor by " Quick Maths "... ?

I know that Its simple Push-Pull method, but when you put OP amp like this, it confuses me so much.

Please explain how this work... using simple words, links, idk.

Happy Holidays to you all.

[Zero999]

The key to understanding the circuit is to look at the internal workings of the amplifier IC. Exactly the same topology can be used to boost the power output of an op-amp. Check out the thread linked below:


https://www.eevblog.com/forum/beginners/non-standard-op-amp-configuration/

[mzdenkov]

Thank you so much.

Best Regards

[David Hess]

I know that his method on picture was invented by Toshiba(it was told to me by professor at my uni).

Tektronix did it back in 1979 with the 741 operational amplifier if not earlier and National Semiconductor application note 29 published in December of 1969 demonstrated the idea as shown below.  With the proper feedback into the output pin, current feedback like performance is possible with a voltage feedback amplifier.

How on earth do i(or amplifier, not me  ) model driving this BD power transistor by " Quick Maths "... ?

I know that Its simple Push-Pull method, but when you put OP amp like this, it confuses me so much.

Please explain how this work... using simple words, links, idk.

The operational amplifier's output current is sourced from its power pins.  If the output current plus the small quiescent current through the base-emitter shunts resistors exceeds Vbe of the transistors, then they conduct pulling the output up or down with higher current than the operational amplifier by itself can provide.