What type of circuit will output 5V when a threshold is crossed?

• What type of circuit will output 5V when a threshold is crossed?
  Posted by Merlysys on 03 Mar, 2014 14:45
• Input peak is unknown, 0~20V
  Output is to be 5V when the threshold is crossed. Threshold should be adjustable.
  Propagation delays, accuracy not important.
  Output goes to logic analyzer(LA) (since LA inputs must be <6V). Circuit is for preliminary investigation of commercially made equipment, laser printer scanner module in this case. I want to see where in the circuit changes occur so they can be examined more closely by oscilloscope.
  
  Is there an IC that will make several of these circuits at minimum size/cost? Best if 8+ points in the circuit can be examined by the LA simultaneously.
  
  Schmitt triggers is probably where I should start at, are there other types of IC based circuits? I looked into transistor based STs as I got lots of transistors lying around but they need several supporting components.
  
  Perhaps there is a completely different approach to this that I am missing.
  
  
  
  
• #1 Reply
  Posted by madires on 03 Mar, 2014 14:50
• I think you're looking for a comparator like LM339.
• #2 Reply
  Posted by deth502 on 03 Mar, 2014 18:13
• yup, comparator.
• #3 Reply
  Posted by Pillager on 03 Mar, 2014 18:45
• I used a 7805 once for turning a 24V-high-signal to a 5V-high-signal. Been working for 3 years.
• #4 Reply
  Posted by w2aew on 04 Mar, 2014 00:37
• Quote from: madires on 03 Mar, 2014 14:50

  I think you're looking for a comparator like LM339.
  

  
  Ditto on the LM339. With the open collector output, it's easy to get any high level you need.