Rules like the push-pull circuit cannot be a PNP top tube and an NPN bottom tube are not mentioned in the textbook. Are there any other rules?

一沙一世

Rules like the push-pull circuit cannot be a PNP top tube and an NPN bottom tube are not mentioned in the textbook. Are there any other rules? [Copy link]

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Rules like the push-pull circuit cannot be a PNP top tube and an NPN bottom tube are not mentioned in the textbooks. Are there other similar rules that are not limited to push-pull circuits? Thank you everyone

Jacktang

What push-pull circuits are mentioned in the textbooks?

Jacktang

"P on top and N on bottom" or "N on top and P on bottom" are two common circuit structures in push-pull circuits.

The main difference between them is the type of tube and the conduction method.

maychang

[Rules such as the push-pull circuit cannot be a PNP top tube and an NPN bottom tube are not mentioned in the textbooks]

Is there such a rule? It seems that it is also possible to use PNP on the top tube and NPN on the bottom tube, but the two tubes are in the common emitter working state, and the driving circuit is very different from that of the top tube NPN and the bottom tube PNP.

chunyang

Not mentioning it means there is no limit. Theoretically, there are four structures of Class B push-pull circuit: upper N and lower P, upper P and lower N, upper N and lower N, and upper P and lower P. The difference lies in the driving method and output method. Among them, upper N and lower P is the simplest in circuit structure. It can be directly driven by the previous stage, and the output can be directly connected to the load or connected to the load through simple capacitive coupling. The upper P and lower P was the mainstream before the 1980s, which was due to the limitations of transistor manufacturing technology. In the 1980s, the upper N and lower P basically replaced the upper P and lower P.

chunyang

P-up, P-down and N-up, N-down require input and output transformers, which are expensive. After the manufacturing technology of NPN transistors matured, the cost of N-up, P-down was lower and the performance was better, so it quickly replaced the transformer-coupled P-up, P-down circuit. N-up, N-down is similar to P-up, P-down, but because NPN transistors were difficult to manufacture, engineers would not make the mistake of adopting this structure.

As for P on top and N on bottom, that requires a very special input and output circuit structure, which is more expensive and has device limitations. It will naturally not be used in practical applications, so it has never appeared.