why totem pole outputs cannot be connected together

I'll add one additional comment which is more directly related to the circuit you show and it's more common function within a larger system. But when the usage is debased, they get misused and confusing, and we have to revert to longer ways to describe what we mean. Well chosen and consistently used names are a useful shorthand. It describes the picture it makes very well, rather than describing the behaviour, and brooks no confusion with a totem pole, which was named after the picture it made.ĭon't get hung up on names, it's the behaviour of the circuit that matters.

A better name for a push-pull output stage would be a 'see-saw' configuration. However it grates to those who use the 'old terms' 'correctly'. It's how language develops, it might even catch on. I'm sympathetic to the mistake, I might even have used words like that when explaining the how and why of a totem pole output to somebody. It's likely the person has heard the term push-pull, and their first exposure to a circuit that had a 'drive in both directions' sort of behaviour was a totem pole. They are totally different circuit used in totally different situations. I can understand why somebody might describe a totem pole output stage as a push-pull, but most people call it a totem pole. This can cause excessive current flow, damaging the transistors and potentially other components in the circuit.The configuration you've shown is the prototypical 'push-pull' arrangement. The problem with connecting TTL circuits with totem-pole outputs together is that if one circuit is in the high state and the other is in the low state, a direct short circuit is created between the power supply and ground through the two transistors. When the circuit is in the low state, the upper transistor is turned off, and the lower transistor is turned on, allowing current to flow from the load through the lower transistor to ground. This allows current to flow from the power supply through the upper transistor and into the load. When a TTL circuit with a totem-pole output is in the high state, the upper transistor is turned on, and the lower transistor is turned off. The totem-pole output stage consists of two transistors connected in series between the power supply and ground, with the output taken from the connection point between the two transistors.

TTL (Transistor-Transistor Logic) circuits with totem-pole outputs are designed to provide fast switching times and low output impedance.

Why totem pole outputs cannot be connected together