I have read that the output stages of some operational amplifiers use push-pull transistor configurations. I was looking over the datasheet for the LM741 and was wondering if this was one of those instances?

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Q14 and Q20 appear to be connected together in a push-pull manner, but their bases are driven independently, or so it seems.

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    \$\begingroup\$ Yep, that's a push-pull output and the VBE multiplier formed by the NPN with R7 & R8 makes it class AB. The bases of Q14 & Q2 are not really being driven independently. \$\endgroup\$
    – John D
    Feb 7, 2015 at 20:33

1 Answer 1


AFAIK the term push-pull is mostly used with digital circuits, but this circuit does indeed both source and sink current.

The two transistors are driven by the same signal (collector of q15/q17), but with a small fixed offset (created by the unmarked transistor with the two resistors) to limit the coross-over distrortian (when the output switches from sourcing to sinking).

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    \$\begingroup\$ "Push Pull" originated with audio output stages, well before transistor logic. In the early 1930s you could get both output devices integrated in the same package... r-type.org/addtext/add019.htm \$\endgroup\$
    – user16324
    Feb 7, 2015 at 20:50
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    \$\begingroup\$ "Push-pull" is a figurative name of a general topology idea that does not depend on the specific implementation (it is even not only an electrical idea). It shows how to build a composite bidirectional (bilateral) source by combining two unidirectional sources - positive (Q14 and V+) and negative (Q20 and V-). Note that "pushing" and "pulling" are created by two different devices that complement each other (thus the other name of this arrangement - "complementary stage"). Also this is the same (half)bridge idea. \$\endgroup\$ Feb 8, 2015 at 8:34
  • \$\begingroup\$ AFAIK a push-pull in TLL chips is made of two NPN transistors - complementatry in purpose, but not in type of device. \$\endgroup\$ Feb 8, 2015 at 9:15
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    \$\begingroup\$ Really the TTL output stage (with another figurative name - "totem pole") is composed by two equal (as a type) but different (as a function) devices - the upper common-collector stage (emitter follower) "pushes" the load, and the lower common-emitter stage "pulls" the load... a pretty ugly configuration... \$\endgroup\$ Feb 8, 2015 at 9:38

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