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'Output Enable' switch using BJT or FET

  1. May 31, 2013 #1
    How to design a Output enable ckt (like the ones in logic gates and buffers) using a simple component like BJT or FET.
     
  2. jcsd
  3. May 31, 2013 #2
    Can you supply some more details?

    Is this an analog or digital circuit?
    How high is the high voltage out and how low is the low voltage out?
    What are the high and low voltage you want to use to enable or disable?
    When disabled, do you want a high voltage, low voltage or just high impedance out?
    When enabled, how much current do you need at the output?
    What is the highest frequency that will be used?
     
  4. May 31, 2013 #3
    Is this an analog or digital circuit?
    >>digital
    How high is the high voltage out and how low is the low voltage out?
    >.3.3V and 0V
    What are the high and low voltage you want to use to enable or disable?
    >>3.3V and 0V
    When disabled, do you want a high voltage, low voltage or just high impedance out?
    >> high voltage
    When enabled, how much current do you need at the output?
    >> 5-10mA
    What is the highest frequency that will be used?
    >> max 10KHz
     
  5. Jun 2, 2013 #4
    Have you considered using a pnp transistor with the emitter connected to Vcc, the collector connector connected to the logic gate output and the base connected through a resistor to be your enable control?
     
  6. Jun 3, 2013 #5
    Where do I get the output?
     
  7. Jun 4, 2013 #6
    The output would still be the logic gate output. All the transistor does is pull the output pin high when not enabled. You will need to check the logic family to see if the gate can stand being pulled high when the output is low. If not, you will need another transistor between the output of the gate and the collector to become high impedance at the same time.
     
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