How would you define VOL and VOH of inverter?

Discussion in 'Homework Help' started by alphacat, Mar 10, 2010.

  1. alphacat

    Thread Starter Active Member

    Jun 6, 2009
    I'm learning about inverters and I know that when:
    Vin = VOL, Vout = VOH
    Vin = VOH, Vout = VOL

    However, what is the meaning of each of them?

  2. vliang

    New Member

    Mar 9, 2010
    are you saying about TTL logic gates? inverter? symbol with a triangle and a small circle?

    if it is, which from my knowledge, i'm using 74ls00 or 74ls04(forgot which is NOT/inverter and which is NAND)

    when an input of 2.5~5v(i'm not sure the max input but too high will break the chip), the out put will be around 0.3v

    When and input of 0~0.8v, the out put will give 5V.

    This actually means there will be a grey region of 0.8V~2.5v.

    In this grey region, the output will still be around 0.3v(i'm not very sure about this last statement)

    Hope it helps
  3. retched

    AAC Fanatic!

    Dec 5, 2009
    Voltage On Low and Voltage On High will be inverted.
  4. Ghar

    Active Member

    Mar 8, 2010
    It's just the name of the output voltage level. The actual numbers depend on the circuit. Like vliang mentioned, a low output isn't necessarily 0 volts, just like a high output isn't necessarily your supply voltage.

    VOH = output high
    VOL = output low
  5. Papabravo


    Feb 24, 2006
    VOH is the minimum output high voltage of the inverter.
    VOL is the maximum output low voltage of the inverter.

    When you connect the output of the inverter to another logic circuit, you must insure that the following inequalities hold:

    1. VOH > VIH
    2. VOL < VIL
    As you might suspect VIH is the minimum Input High voltage of a logic gate, and VIL is the maximum input low voltage. Here is the really important point: Any voltage between VIL and VIH is no mans land. A voltage in that range will result in an unpredictable output. This may happen with a disabled tri-state output when it is in the high impedance state.
  6. kdillinger

    Active Member

    Jul 26, 2009
    If you now the thresholds, L's and W's you can calculate the output voltage.:cool:

    It is also a point where Icc is high.
  7. alphacat

    Thread Starter Active Member

    Jun 6, 2009
    wow, thank you very much for explaining it to me.

    Are there terms for 'Minumum Output High Voltage' and 'Maximum Output Low Voltage'?

    I assume that:
    'Minumum Output High Voltage' = Vout(Vin=VIL)
    'Maximum Output Low Voltage' = Vout(Vin=VIH)