# TTL logic based Question

#### M.Naumann

Jan 22, 2017
4
Hallo all. This is my first post in this forum. I need some description about the some TTL based Logic. I have attached the Picture of My question for details so I shall be really grateful to you people if somebody spares his time .I shall be grateful to you. Thanks in advance.

My Question:

1- How this logic works for this the circuit. Actually I want to calculate the Voltages across transistors. How to calculate those voltages. Can someone please explains me..
Means Accross T1 ,T2 T3, and T4 and for cases when X1,X2 is 0,0 --- 0,1-----1,1

Jun 21, 2012
4,792

#### M.Naumann

Jan 22, 2017
4
@hevans1994 thx for ur reply. I have studied the stuff and no its not homework problem .. I am preparing for an exam . I can apply logic and get the output but I am confused with the Calculation of Voltages across the circuit. Posted it to clarify my confused concept.

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,792
Well, the TI datasheet says the emitter inputs sink 0.4 mA when low. Does that help with your circuit analysis? Why would an exam care about the internals of an ancient and obsolete logic integrated circuit? What is the exam for? Just curious. I am afraid I can't be of more help.

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,054
Try to understand this analysis of a TTL circuit.

By the way: I didn't see any sense in your poll, therefore I deleted it. Just in case: There is no need to add a poll to a thread, this is optional.

#### hevans1944

##### Hop - AC8NS
Jun 21, 2012
4,792
Thanks, Harald! That link you provided has a wealth of information on how TTL circuits were implemented, things I haven't visited in more than forty years. You are a fountain of good information!

#### M.Naumann

Jan 22, 2017
4
Well, the TI datasheet says the emitter inputs sink 0.4 mA when low. Does that help with your circuit analysis? Why would an exam care about the internals of an ancient and obsolete logic integrated circuit? What is the exam for? Just curious. I am afraid I can't be of more help.

@Heaven1944 thanks a lot for your help . Actually we have studied from some obsolete stuff then they told us that why we are not using those and why we moved toward new areas. Its related to Communication system and protocol. There are lot of stuffs which r part of this course but this is one of it.

#### M.Naumann

Jan 22, 2017
4
Try to understand this analysis of a TTL circuit.

By the way: I didn't see any sense in your poll, therefore I deleted it. Just in case: There is no need to add a poll to a thread, this is optional.

Thanks a lot for the provided link . I study this and then come back if i find some issue. Thanks for your help and time.

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