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Some doubts in open collector TTL

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SherlockBenedict

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In open collector TTL it is necessary that you should have a pull up resistor for proper operation. It is also said that if you are connecting one TTL to another TTL, even if you don't connect the pull up resistor it work properly. How is that so? I mean when the output transistor is saturated (or ON in other words) the output capacitor voltage will be about 0.2V and when it is open (or OFF in other words) and if we assume that the capacitor doesn't discharge it will have a value of 0.2 V only and not 3.6 V. Then how does that work without a pull up resistor?

Thanks a lot. :grin::grin::grin:
 

The input current from the following stage will pull-up the OC output. However, I don't think this is a very good way of using the OC output.
 

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