Sziklai transistors: What’s that?
A while ago, a potential Design Idea crossed my desk, and it contained an unusual transistor pair the author called a Darlington, except, it wasn’t.
A bit of research turned up the configuration: It’s called a Sziklai pair, named after Hungarian-American engineer George Sziklai.
Figure 1 NPN Sziklai pair (source: The Art of Electronics)
Yes, my old Art of Electronics mentions it in passing as part of the Darlington “chapter”. The characteristics are similar to a Darlington pair, but with only a single VBE, not two, but still possessing the VBE saturation limitation.
According to Wikipedia, Sziklai pairs are relatively common in audio amp output stages due to bandwidth and linearity advantages over Darlington pairs, as well as lower quiescent power and easier thermal compensation. And Rod Elliott provides a pretty thorough analysis on his audio site.
The Sziklai pair. Sounds like a good circuit to add to your arsenal.
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—Michael Dunn is Editor in Chief at EDN with several decades of electronic design experience in various areas.