EEVblog® Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: Alex QW on March 14, 2023, 05:57:55 am
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Hi all,
May I know how this TTL load circuit work as shown in the below diagram?
Note that: 1)the red arrow means the microcontroller control signal (1,2)
2) Is the TTL output pin (3,4)
The circuit is in this link: https://forum.allaboutcircuits.com/threads/ttl-load-circuit.192516/
Thank you.
Best Regards
Alex.
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Erm. I'm not registering with your website.
You didn't give out any information on your circuit there either!
A TTL load is an equivalent circuit of a TTL gate input.
Have a look at the TTL wiki page.
see www.interfacebus.com/Glossary-of-Terms-TTL-Load-Circuits.html (http://www.interfacebus.com/Glossary-of-Terms-TTL-Load-Circuits.html)
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May I know why they use a lot of diodes in the circuit?
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Attach the picture of your circuit here. Most people can't see it on allaboutcircuits.com since we don't have an account.
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This is the circuit diagram
Note that: 1)the red arrow means the microcontroller control signal (1,2)
2) Is the TTL output pin (3,4)
Sorry for any inconvenience as I just joint this forum not so familiar with this feature
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The bias resistors set up a current (1.2mA) in the diodes going to ground- this sets VIL for the equivalent gate input plus a diode drop. You then subtract a diode drop ((D604) from this voltage.
This sets the lower threshold to a bit over VIL.
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how to know that the bias resistors set up a current (1.2mA)?