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I can't understand/see the difference between a push pull, for example a circuit like that:enter image description here

And a Totem-Pole: enter image description here

Have these circuit a transistor in the input so for get a thing like "double amplification"?

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    \$\begingroup\$ A Totem-Pole output is often used for logic gates and some op-amps because it allows the output to approach ground potential, or zero volts. The Push-Pull output cannot approach either power rail due to a Vbe drop of .6 to 1.2 volts. That is just a comment, not an answer to your question. \$\endgroup\$ – Sparky256 Feb 24 '18 at 20:59
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    \$\begingroup\$ This line from a website I have forgotten the address says it all: "Totem-pole and push-pull I/O are functionally the same, but the former require inputs of opposite polarity for same polarity transistors, while the latter uses transistors of opposite polarity driven by the same input." Be aware that the terms are somewhat loosely used and sometimes people call push-pull a totem pole and vice versa. \$\endgroup\$ – Sredni Vashtar Feb 25 '18 at 2:42
  • \$\begingroup\$ As for the double amplification, with a single transistor you usually place the operating point in the middle of the characteristics to accommodate both positive and negative swings of the output signal, while when using push-pull, you can place it at the cut-off border and make the output swing only in one 'direction' for each transistor, achieving double the swing with a single transistor. \$\endgroup\$ – Sredni Vashtar Feb 25 '18 at 2:47
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You'll notice in the push pull stage that you need a PNP and an NPN transistor, whereas the totem pole driver uses only NPN transistors. This is useful because NPN type transistors are usually easier to make, and support higher current for a given size than PNP type transistors.

To address your question on "Double amplification", a push pull driver doesn't necessarily give more amplification, but is used because it is more efficient than a single transistor amplifier because (ideally) only one transistor is on at a time, and all the current goes through the load.

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  • \$\begingroup\$ Your final (incomplete?) paragraph ignores the existence of Class A. \$\endgroup\$ – user207421 Feb 25 '18 at 1:09
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I’ve always thought of push pull as a type of output realized by many different configurations and a totem pole is one of the configurations as is compound, complementary.

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