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???
07/01/11 09:40
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Msg Score: +1
 +1 Good Answer/Helpful		 #182772 - open emitter
Responding to: ???'s previous message
Santosh said:
hi, what is the meaning of open emitter output .
at the output of udn 2892 we are getting -500mA of current what that really means.

At page 3 of this datasheet

http://www.allegromicro.com/en/Produc...1/2981.pdf

you will find the schematic of circuit being inside an UDN2982.

If the input is high, current flows through the 20k resistor. By this the PNP turns on and drives the output transistors, which are configured as a NPN Darlington transistor.

Read more about Darlington transistor here

http://en.wikipedia.org/wiki/Darlington_transistor

This Darlington transistor has the collector connected to the positive supply and the emitter to the output, so that current can be delivered into an external load by the UDN2982, which flows out of the emitter of Darlington, through the external load and finally to ground.

Because nothing else is connected to the emitter, this output is called "open emitter".

Kai Klaas

List of 49 messages in thread
TopicAuthorDate
problem rgarding uln and udn            01/01/70 00:00      
   They are different in every sense!            01/01/70 00:00      
      problem rgarding uln and udn            01/01/70 00:00      
         You forgot your links            01/01/70 00:00      
         Basic electronics            01/01/70 00:00      
            Clarification - more Basic Electronics            01/01/70 00:00      
            probelems regarding udn 2892            01/01/70 00:00      
               Still Basic electronics            01/01/70 00:00      
                  Links            01/01/70 00:00      
                     That'll be why he's still struggling after all these weeks!            01/01/70 00:00      
               open emitter            01/01/70 00:00      
                  Open collector            01/01/70 00:00      
         RE: i am not getting you            01/01/70 00:00      
   Did you really read datasheets?            01/01/70 00:00      
      problem rgarding uln and udn            01/01/70 00:00      
         relay matrix???            01/01/70 00:00      
         This doesn't make sense!            01/01/70 00:00      
            8x8 relay matrix?            01/01/70 00:00      
               relay matrix?            01/01/70 00:00      
                  not quite            01/01/70 00:00      
                  one interesting thing I learned            01/01/70 00:00      
               Unless...            01/01/70 00:00      
                  problem rgarding uln and udn            01/01/70 00:00      
                     lightning fast relays            01/01/70 00:00      
                        problems regarding uln and udn            01/01/70 00:00      
                           both            01/01/70 00:00      
                           None of this makes sense!            01/01/70 00:00      
                           It appears you need latching relays            01/01/70 00:00      
                              Latching relay is still slow            01/01/70 00:00      
                                 You're right, but the relay spec's should reveal that            01/01/70 00:00      
                              well, if he does ...            01/01/70 00:00      
                                 use toggle types ... they were around once ...            01/01/70 00:00      
                                    SPI + latched shift registers are good choices            01/01/70 00:00      
                                       The protocol is good ... but not necesary here            01/01/70 00:00      
                                          SPI is excellent for driving long shift registers            01/01/70 00:00      
                                             tell us, Per, what data types does SPI support?            01/01/70 00:00      
                                                Making Mountain Out Of Mole Hill            01/01/70 00:00      
                                                   protocol and/or command structure            01/01/70 00:00      
                                                No, SPI does *not* have both commands and data!            01/01/70 00:00      
                                                   Where you sit determines what you see            01/01/70 00:00      
                                                      Totally missing the point            01/01/70 00:00      
                                                         The major advantage            01/01/70 00:00      
                                                      Where Richard Sits......            01/01/70 00:00      
                                                         From where I sit...            01/01/70 00:00      
                                                      Always important to follow up the progress of technology            01/01/70 00:00      
                     Language barrier?            01/01/70 00:00      
                        Further question            01/01/70 00:00      
                     Sorry, double posting...            01/01/70 00:00      
   Cross-Post?            01/01/70 00:00      

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