I am using the LM139 comparator chip. Now, I understand that the output of the comparators,or for that matter op amps are open drain/collector. SO they can only sink current and not source it per se.
I had a glimps of the data sheet which says Iout = 20mAmps. Is it the max current that it can sink ?
The datasheet screen shot is –
.
Also, in the LT1716, the output pin is stated as – "The output stage of the LT1716 can drive loads connected
to a supply more positive than the device, the same as
comparators with open collector output stages.".
Does this mean it (output load) has to be connected to a different voltage rail. Suppose I connect the comp to 44V (Vcc), then effectively the Load should be connected to a voltage rail > 44V.
Are my assumptions right ?
Best Answer
If you don't care if it works and about reliability, then you are correct. In general you should never use 'absolute maximum' ratings for designing limits of normal operation- only to get an idea whether the device would survive a brief abuse of that magnitude.
A more conservative number is the current at which the maximum output 'low' voltage is guaranteed- 4mA. A prudent designer would derate that for the fact that the guarantee only holds for 25 degrees C - it would typically be worse at low temperature, so maybe 3mA for 500mV max drop.
Your interpretation of the Linear datasheet is correct- the load can be connected from the output to a voltage rail that is higher (or lower) than the chip supply voltage.