Other Parts Discussed in Thread: LM2903, LM2901
Hi all,
I am using LM2904 to mimic the behavior of, the seemingly very similar, LM2903 in bench testing for a new design. Essentially, 2904 is acting as a comparator. This is only a temporary, makeshift solution until my LM2903 chips arrive. Unfortunately, I have noticed an issue while testing 290 and I cannot determine its cause.
I am taking one of two outputs of an amplifier, biased at 1/2 the supply voltage of about 5 V, and comparing that to a reference voltage. I would then like LM2904 to compare the speaker output voltage with the reference voltage, saturate, and potentially drive an LED. The idea here is that depending on which input is greater the LED will turn on or off.
My problem is that under idle conditions, LM2904 provides a surprising output because, although input 2IN+ is greater than 2IN-, 2Out is going low. My expectation is that, given the idle conditions, the output should be high.
Could someone could shed some light as to what may be happening, whether or not this is probably being caused by the chip, and whether or not I may have the same issue using LM2903?
For reference, I have included the idle voltage points of the pins of interest and a schematic of that part of my design. Thank you in advance.
Pin 4: 0 V
Pin 5: 2.453 V
Pin 6: 2.297 V
Pin 7: 0.738 V
Pin 8: 4.854 V