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???
07/09/09 00:38
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 		 #166891 - To what do you connect the source of this pMOSFET??
Responding to: ???'s previous message
Richard said:
Some of these have very low threshold voltages, hence will operate just fine under control of an MCU at 3V3.

Does that mean that the source of pMOSFET is connected to Vcc of SILABS micro (which is 3.3V) and that the output of micro turns on the pMOSFET by pulling down its gate to 0V?

But Raj told, that he wants to turn on a 5V relay. How do you want to accomplish this by the above scheme? By connecting the relay between drain and 0V? This would only yield about 3.3V to turn on the 5V relay.

Kai

List of 33 messages in thread
TopicAuthorDate
Driving a 5 v PNP with 3.3 volts pin            01/01/70 00:00      
   Diagram ?            01/01/70 00:00      
      Sketch..            01/01/70 00:00      
         Steve..            01/01/70 00:00      
            Why push-pull?            01/01/70 00:00      
               Thanks Rob            01/01/70 00:00      
               Very much depending on chip            01/01/70 00:00      
                  Yeah, but ...            01/01/70 00:00      
                     Better always add a note for potentially dangerous methods            01/01/70 00:00      
                        Is that my responsability?            01/01/70 00:00      
                  Westermark            01/01/70 00:00      
                     Erik did exmplain            01/01/70 00:00      
                        Sorry Westermark..            01/01/70 00:00      
         KISS            01/01/70 00:00      
   If it has not to be a PNP...            01/01/70 00:00      
      Relay has to be driven..            01/01/70 00:00      
         since I would never do that ...            01/01/70 00:00      
            Open drain pulled up to 5V..            01/01/70 00:00      
               did you read my post            01/01/70 00:00      
                  Deep waters            01/01/70 00:00      
                     OK, more            01/01/70 00:00      
                        I missed this post..            01/01/70 00:00      
      BC556 would turn on, wouldn't it?            01/01/70 00:00      
         It wouldn't. Sorry.            01/01/70 00:00      
   Have you considered a pMOSFET?            01/01/70 00:00      
      Yep, I second that! Use a FET            01/01/70 00:00      
         Have you considered that he must drive a 5V relay?            01/01/70 00:00      
            Does that really matter?            01/01/70 00:00      
               To what do you connect the source of this pMOSFET??            01/01/70 00:00      
                  It's the switched drain current that does the work            01/01/70 00:00      
                     Of course, it does! But...            01/01/70 00:00      
                        One could also use a "switch" ...            01/01/70 00:00      
                           Yes, that's safe!            01/01/70 00:00      

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