So I was looking at the Data sheet for the TL081CP OP AMP. Specifically at the transitor level schematic, which I have attached. Now, say the output of the op amp to swings from rail to rail ( From say, +10V to -10V).

Ok, so here is my question. Looking at the output stage of this op amp, which mainly consists of a npn and pnp transistor.When the output of the op amp is positive, then current flows from (+)Vcc, through the npn transistor, and to the output ( It is sourcing current). When the output of the op is negative, the current flows from the output, through the pnp transistor, to
(-)vcc ( Sinking current). Is this correct? Or am I looking at it wrong.

Thanks a mil.

 

It's not a rail-to-rail output, but we'll go with that for the moment

As far as your 2nd paragraph - yes, that's correct.

 

Ok, so my second paragraph is correct, thats good.

Can you elaborate on why it is not rail to rail? It can be configured to be as such no?

Thnks

 

Opamps with a rail-to-rail output usually are a CMOS type. The TL081 has emitter-follower junction transistors on its output and can swing to within about 1.2V to a supply rail without a load, to within 1.5V with a 1.4mA load and to within about 5V with a 10mA load.

The TL081 and other old FET-input opamps have a problem that is called phase inversion. If an input gets to within about 3V from its negative supply voltage then its output suddenly inverts.