Q2 & Q3 form a complementary push-pull output pair - less commonly implied by totm pole terminology. See diagram below - two for the price of one. This is usually what is implied by the term. See diagram below - classic totem-pole output with drivers of same polarity at top and bottom. As there is no Valve equivalent to a PNP transistor, complementary pair designs were not possible. The term originally was used in pre transistor thermionic valve designs where two stages were placed in series in the same manner. This arrangement has become so common that it is often what is envisaged when the term "totem pole" is used, even though a complementary pair can serve the same purposes. Nothing new added.Ī totem pole driver or output stage is a loose term used to mean that the output is driven actively in both the high and low directions.Ī totem pole output can be an NPN/PNP or N Channel/P Channel "complementary pair" or, as is the case in many TTL logic devices, two devices of the same polarity stacked on top of each other. *- Points in this summary are already covered below. I guess it has to do with the low-voltage process, but it does take away the open drain's most interesting feature.Ī totem pole driver or output is fast and relatively "powerful" when switching in either direction compared to passive resistor stages or current source or open collector loaded stages.Ī totem pole arrangement is not suitable for paralleling with other divers to make "wired OR" stages - which can be useful in some applications.Ī totem pole driver switches "between its supply rails" so cannot drive loads which are connected on one end to voltages outside the supply rails - as is required in some applications. When the load you're driving goes beyond \$V_\$.CMOS totem-poles are more symmetrical, and don't suffer from this. So don't use them when you need to both source and sink current. TTL totem-poles are highly asymmetrical: they can hardly source current, typically 0.4mA versus 16mA when sinking.Always use open collector/open drain drivers for wired AND. If one output is high and the other low you get a short.
You can't use totem-poles for wired AND (often called wired OR, but most often they're ANDs).
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