I don't understand well the difference between push-pull and half bridge. Someone told me it was totally different but as I understand it, half bridge is a generic name where we have 2 switches and a load connected in the middle. So I guessed that push-pull circuit is just a kind of half-bridge. Is that correct?
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1\$\begingroup\$ I would consider a half-bridge to have a more limited scope than a push-pull driver. But if you hang only on the point about being able to source and also sink current, they are similar. A half-bridge usually carries a "switch nature" to it, in that you will either switch the high side or the low side (or neither, but never both.) So a half-bridge doesn't usually imply a linear operation. A push-pull driver might very well be designed for and provide linear operation and not just switching. But I'm a hobbyist. So I'll let the professionals give you the gospel. It's their turf. \$\endgroup\$– jonkJun 4, 2017 at 2:02
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2 Answers
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A half-bridge is a specific style of push-pull stage where the two active elements are in series across the supply and they alternately conduct to supply current to the load. The name usually refers to a switching output stage rather than one with linear control or only low power output.
The term push-pull refers to any type of circuit where there are two active devices that each drive one half-cycle of the signal - one pushes and the other pulls.
The devices can be in series across the supply or both be between the supply and ground and use a transformer to combine the two halves. They can be be used in linear mode for analog signals or just on/off for switching purposes.
The active devices can be any type of device such as FETs, electron tubes (valves), bipolar junction transistors etc.
Here are some examples:
Half-bridge:
Transformer coupled push-pull:
Complementary push-pull:
TTL output stage:
answered Jun 4, 2017 at 4:04
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\$\begingroup\$ But what do you mean by "output stage"? Does it mean you cannot use a push pull in a middle of an electronic circuit? You can just use it in the output? \$\endgroup\$– edamondoJun 4, 2017 at 16:59
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\$\begingroup\$ It can be used anywhere but is most common where significant power is required. \$\endgroup\$ Jun 4, 2017 at 17:46
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1\$\begingroup\$ Emitter is marked "collector". Shorts out my mind. \$\endgroup\$– user76844Jun 4, 2017 at 17:47
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\$\begingroup\$ @GregoryKornblum - thanks I didn't notice that on the image I snagged from the web - corrected. \$\endgroup\$ Jun 4, 2017 at 17:56
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I have always felt push pull was a bit of a misnomer as the two active switches are generally connected to the same polarity, which would give a push push (if switching negative) to the center tap ( positive). And a bipolar supplied output stage would be a push pull.
