I'm reading an article about how a rail-to-rail opamp works. The materials from Maxim and Analog Device all mentioned that, in a conventional operational amplifier, the output stage, in its essence, is a pair of NPN/PNP forming an emitter follower.
One can instantly recognize that the principle of operation is similar to a push-pull output stage found in discrete Class-AB amplifiers, the output stage is used as a buffer for current gain. The input is at the center of the diodes, and since it's an emitter follower, the output is a replica of the input. This arrangement comes with a Vbe drop, with means the output can never get to the power rails.
The articles continue to explain that in order to overcome this limitation, in a rail-to-rail opamp, the output stage is a pair of PNP/NPN transistors forming an common-emitter amplifier. And in this arrangement, the maximum output swing is only limited by Vce_sat, and is able to get very close to the rail.
But I have never seen this configuration before (The only time I've seen it before, is in The Art of Electronics as a bad example of a miswired Class-B amplifier - once an input is applied to the bases, both transistors are turned on and they blow up...).
How does this output stage supposed to work? How do I apply an input? Are there some practical examples of this circuit with discrete transistors?