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Per Westermark
03/15/12 11:02
  03/15/12 11:02

Read: 552 times

Msg Score: +1
 +1 Good Answer/Helpful
#186701 - No best but consider a voltage divider
Responding to: Mehdi's previous message
There are almost never any "best" design.

You can do a voltage divider solution where one pin drives the divider to 50% of max amplitude. Second pin has zero ohm pull-up resistor so when high signal goes all the way to VCC. Or (since this is 8051 site) consider the reverse. One pin draws resistor to GND. Second pin draws to GND with zero ohm resistor.

If you need to load the signal, you may need to buffer it. Just that analog buffers (like an OP-Amp) normally can't match the rise/fall times of digital signals.

List of 21 messages in thread
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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