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Richard Erlacher
03/15/12 16:30
Read: 518 times
Denver, Co
USA


 
#186711 - maybe a couple of mosfets ...
Responding to: Mehdi's previous message
and a couple of resistors ...

If you have a couple of resistors configured as a divider between Vcc and Gnd, and you then use a mosfet pair, usually an N-channel and a P-channel in an soT of some sort, often costing MUCH less than $1.00US, you can pull to GND with the N-channel, and to Vcc with the P-channel, using each of two I/O pins. When the P-channel is "ON", you conduct from Vcc to the mid-voltage of the divider, and when the N-channel is "ON", you conduct from the mid-voltage to GND, and when neither is "ON", you have the mid-voltage node of the divider. Buffering the mid-voltage to the output through an NPN voltage follower would not be a bad idea, depending, of course, on the required output impedance. Those MOSFET's, BTW, are inverters, so pay attention so you don't turn both of them "ON" at the same time.

RE


List of 21 messages in thread
TopicAuthorDate
Making a pulse with 3 different voltage level!      MEHDI      03/15/12 10:57      
   No best but consider a voltage divider        Per Westermark      03/15/12 11:02      
      derivative with a DAC?      Erik Malund      03/15/12 11:07      
   derivative with configurable ports        Erik Malund      03/15/12 11:10      
   Thanks Per And Erik      MEHDI      03/15/12 11:44      
      which derivative      Erik Malund      03/15/12 12:12      
      with an OPamp      Erik Malund      03/15/12 12:16      
         Thanks Erik      MEHDI      03/16/12 01:57      
      So, you need to make -15V, 0V and +15V?      Kai Klaas      03/16/12 06:38      
         Hi Dear Kai      MEHDI      03/16/12 09:45      
         74hc series      MEHDI      03/17/12 12:50      
            FPGA      Kai Klaas      03/17/12 14:58      
      I think you can do it wih one resistor.      David Prentice      03/16/12 11:09      
         Most 8051 Systems?????      Michael Karas      03/16/12 18:51      
            Well add a pull-up resistor then      David Prentice      03/17/12 02:34      
               Would prefer to not have to match internal resistors      Per Westermark      03/17/12 06:48      
               You cannot match the weak internal active pull-up!      Kai Klaas      03/17/12 07:02      
                  Being pedantic.      David Prentice      03/17/12 09:12      
         Hi David      MEHDI      03/17/12 12:43      
   maybe a couple of mosfets ...      Richard Erlacher      03/15/12 16:30      
      Thanks Richard      MEHDI      03/16/12 02:02      

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