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???
02/25/09 17:55
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 		 #162835 - LM339 is an open collector
Responding to: ???'s previous message
Aamir wrote "I have a LM339 comprator".It will never produce logic HIGH at its output without a pullup resister becuase LM339 is an open collector output.Use a pullup resistor on output pin.

List of 27 messages in thread
TopicAuthorDate
comparator with 8051            01/01/70 00:00      
   What have you tried?            01/01/70 00:00      
      description of project            01/01/70 00:00      
         Look at photo transistor            01/01/70 00:00      
            further description            01/01/70 00:00      
               But why 7V ?            01/01/70 00:00      
   Another project?!            01/01/70 00:00      
      this is another project            01/01/70 00:00      
   Not a sinusoidal waveform!            01/01/70 00:00      
      Well, it can look like a sine...            01/01/70 00:00      
         still problem with comparator            01/01/70 00:00      
            Circuit missing            01/01/70 00:00      
            sorry the circuit is here            01/01/70 00:00      
               the circuit            01/01/70 00:00      
                  Why bandages, and why 9V VCC?            01/01/70 00:00      
                  VREF is wrong!            01/01/70 00:00      
               How is Vref 4V ?            01/01/70 00:00      
            used two diodes at input to MCU            01/01/70 00:00      
               Doesn't solve the Vref problem!            01/01/70 00:00      
   kai, help me with comparator            01/01/70 00:00      
      Give this a try...            01/01/70 00:00      
         thanks            01/01/70 00:00      
         thanks, the circuit worked            01/01/70 00:00      
   LM339 is an open collector            01/01/70 00:00      
   As Aamir Javaid said about input to 8051.            01/01/70 00:00      
      Not for an open-collector output!            01/01/70 00:00      
         Is that tied to +5VDC            01/01/70 00:00      

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