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converting signal to ttl logic voltage level converting signal to ttl logic voltage level
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Old 3rd September 2004, 07:44 PM   (permalink)
Default converting signal to ttl logic voltage level
Hi,
I have this weird output. When the signal is true, the voltage is 5.0V, but when it is false, the voltage is 3.3V. I need to convert this to a ttl logic level, so that it remains 5.0V when it's true, but it changes the 3.3V to 0V when it is false. Does anyone know if there is a component that does this? I really need suggestions.
Thanks ops: :shock:
ptewright is offline  
Old 3rd September 2004, 07:47 PM   (permalink)
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A zener...
Exo is offline  
Old 3rd September 2004, 08:09 PM   (permalink)
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a schmitt trigger?
Gaston is offline  
Old 3rd September 2004, 09:31 PM   (permalink)
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A possible solution...
Attached Images
File Type: gif levelshift.gif (1.6 KB, 487 views)
Sebi is offline  
Old 3rd September 2004, 09:45 PM   (permalink)
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another choice, a comparator (maybe an lm311)
crust is offline  
Old 4th September 2004, 07:26 PM   (permalink)
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How's about a PNP with a pullup to +5 on the emitter (collected grounded, signal to base)? The pull up also limits base current.

j.
John Sorensen is offline  
Old 5th September 2004, 03:05 AM   (permalink)
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Below is a 2-transistor solution which is noninverting. Sebi's circuit will invert. John's circuit is an emitter follower, and the output will swing from 4v to 5v as the input swings from 3.3v to 5v. A comparator such as LM311 or LM393 will work.
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File Type: gif level_shifter.gif (5.1 KB, 444 views)
Roff is offline  
Old 5th September 2004, 03:53 AM   (permalink)
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Quote:
John's circuit is an emitter follower, and the output will swing from 4v to 5v as the input swings from 3.3v to 5v.
I'm so embarrassed ops:

j.
John Sorensen is offline  
Old 9th September 2004, 05:20 PM   (permalink)
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Quote:
Originally Posted by Ron H
Below is a 2-transistor solution which is noninverting. Sebi's circuit will invert. John's circuit is an emitter follower, and the output will swing from 4v to 5v as the input swings from 3.3v to 5v. A comparator such as LM311 or LM393 will work.
What would the circuit for the comparator look like?
ptewright is offline  
Old 9th September 2004, 06:11 PM   (permalink)
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Solution with comparator...
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File Type: gif levelshift_103.gif (2.9 KB, 396 views)
Sebi is offline  
Old 9th September 2004, 10:43 PM   (permalink)
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Sebi, the input swings from 3.3V to 5V, so the threshold should be 4.15V.

See below.
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File Type: gif levelshift_354.gif (2.9 KB, 386 views)
Roff is offline  
Old 10th September 2004, 06:41 AM   (permalink)
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Right, Ron... I'm wrong in mathematics... ops:
Sebi is offline  
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