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LM393-N: about IN+/IN- terminals

user6150189
Intellectual 460 points
Part Number: LM393-N
Other Parts Discussed in Thread: LM393

Please answer the following two questions.

①. Please tell me the input impedance and variation of the IN + / IN- terminals.
②. If the input voltage of the IN + / IN- pins is the same (when the Input Offset Voltage is less than 1 mV), will the OUT pin be a LOW output?

  • 0
    TI__Mastermind 49906 points

    Hello,

    1. The inputs have about 20nA of current coming out of the input pins flowing towards ground. This current is fairly consistent over the valid input range, and falls to pA's when above the input voltage limit.

    Please see the LM393 family appnote, section 2 for more information:

    Application Design Guidelines for LM339, LM393, TL331 Family Comparators (Rev. A)

    2. Offset voltage can be positive or negative, so when the inputs are at the same potential, the output could be high or low. Theoretically, you have a 50/50 chance of a high or low output at zero. A properly designed circuit should have a slight bias (a little more than the maximum offset voltage) applied to the inputs to prevent "random" outputs at low levels.