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???
08/26/05 08:37
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#100124 - not good idea
Responding to: ???'s previous message
hi,

Peter Dannegger said:
To drive a transistor, put the base direct on the 8051 port pin and a resistor from base to VCC.

...and it will work with pins of port 0 only.

With others ports you have a good chance to burn base-emitter of transistor each time when there is 0-to-1 transition on a pin. Why? Because strong pull-up pFET1 is turned on for 2 osc. periods. Read http://www.8052.com/forum/read.phtml?id=93728

Here is corrected schematic by Michael: http://www.8052.com/forum/read.phtml?id=93726

Regards,
Oleg

List of 17 messages in thread
TopicAuthorDate
I need help with LED Driver            01/01/70 00:00      
   LED            01/01/70 00:00      
      LED            01/01/70 00:00      
   use a LED driver            01/01/70 00:00      
   74LS drivers            01/01/70 00:00      
   LED Driver - My Solution            01/01/70 00:00      
      quite risky            01/01/70 00:00      
         MCU-resistor-NPN            01/01/70 00:00      
            8051 is open drain !            01/01/70 00:00      
               not good idea            01/01/70 00:00      
                  totally wrong !            01/01/70 00:00      
                     This I would take with a grain of salt.            01/01/70 00:00      
                     But nevertheless totally unsuited!            01/01/70 00:00      
            Where in Atmel errata or other informati            01/01/70 00:00      
               That's standard performance of quasi bi.            01/01/70 00:00      
      Try This            01/01/70 00:00      
         updated            01/01/70 00:00      

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