LM319 - output voltage

Hello Hirotaka,

The LM319 is an open-collector (O.C.) output. It *requires* an external pull-up for the output to go high. The output is not designed to source current.

Note that all the example schematics have a pull-up resistor, or a load tied to V+. Once you have proper value pull-up resistor, then the output will go to 5V. DO NOT rely on the internal leakages to pull the output high.

Also, the LM319 is not a rail-to-rail input device. The valid input range is +1 to +3V with a +5V supply (I am assuming V+=5V, V-=GND).

If the output is high, the input common mode range is violated (3.75V at +IN).

If your input sine wave is below 1V, or above 3V, it is in the "illegal" range, and the output can be in the wrong state when the input range is violated - possibly causing a "latch" condition with your circuit if a reversal occurs.

For your circuit above, with an input signal going 0-5V, you need a Rail to Rail input and output device like the LMV7239 or TLV3201 (assuming you need the ~100ns speed). Otherwise, there are numerous slower R-R I/O comparators to choose from.

Regards,

Hello Hirotaka,

The 5V spec line is for a "Single" supply, with V+=5V and V-=GND. The reference point is GND for single supply.

The spec applies to both inputs. Neither input should be less than 1V and greater than 3V.

The common mode voltage is NOT the average of the two inputs, as comparators can have several volts difference between the inputs. The spec is PER INPUT.

Regards,