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Totem pole outputs creates glitches?

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Ericwatson

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Is it true that totem pole outputs create glitches in the power rails compared to using open collector output chips which don't create glitches on the power rails?
 

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Most of us do not see anymore the totem pole outputs that were in old TTL logic ICs.
Modern Cmos outputs are complementary push pull but have a low current. High speed Cmos push pull outputs conduct so much current when their voltage is halfway that they have a minimum switching speed so that they do not overheat while shorting the power supply.

If you read about Push Pull Outputs in Google then they talk about a TTL totem pole output that always has the top transistor conducting so when the lower transistor turns on then the supply current suddenly increases which causes a glitch in the power supply voltage and current.
This is one reason that every[/c] old TTL logic IC needed its own supply bypass capacitor.
 

Ericwatson

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So open collector IC chips don't need decoupling capacitors for each logic IC chip since they don't create glitches. Can I replace TTL totem pole IC chips when a TTL open collector IC chip using the same part number?
 

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Can I replace TTL totem pole IC chips when a TTL open collector IC chip using the same part number?
No, because they don't exist. There's only a limited number of o.c. devices, and they have unique part numbers.

Generally, you are misunderstanding the purpose of open collector circuits.
 

Ericwatson

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If you're repairing old logic TTL board that used totem pole logic chips, you can't replace them with new TTL open collector logic chips using the same pin out and same part number. Any reasons why you can't interchange them?
 

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Because there are no o.c. part with the same part number.
 

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An open collector TTL IC needs an additional collector pullup resistor to the +5V supply for each output. Where will the resistors be mounted?
 

Ericwatson

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So what does a repair technician do when logic boards that have bad logic chips that are totem pole outputs.
 

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So what does a repair technician do when logic boards that have bad logic chips that are totem pole outputs.
It should be obvious that if a logic chip is bad then you replace it if you can still find any of the very old chips you seem to work with.
How do you know when a logic chip is "bad"?
Why were you talking about glitches on the power rail? Maybe a supply bypass capacitor is bad instead of a bad logic chip? In the 70ies, every tantalum supply bypass capacitor I looked for were gone because they literally blew up. Then the old TTL logic ICs went haywire.
 

Ericwatson

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If I have a bad logic IC chip that is totem pole output , how can I interface and replace it with a logic IC chip that has a open collector output. Repair technicians must get older logic TTL board with IC chips that are totem pole outputs. What does the Repair technician do when they have to replace bad IC chips that are totem pole outputs since they can't interchange and replace them with new good IC chips using open collector outputs. Does the Repair technician have to do some type of interfacing network or circuit for it to work?
 

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Why do you want to replace a bad chip with a completely different chip instead of using an exact same chip as the original one?
How do you know the original chip is bad? A guess?
 

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