I have two questions regarding the electrical characteristics of comparators:
- Is there a way to adjust the input offset voltage of a comparator to fit a custom application?
- Which comparator output type is the ideal choice for powering an LED circuit?
I am designing a circuit that will detect a failed LED (open or short circuit) by comparing two voltages and triggering a second LED, indicating a failure if the voltages ever differ. I am having trouble sourcing a comparator chip that will allow the correct amount of voltage fluctuation at it's inputs. For example, if the voltage fluctuates by 100mV this should not trigger the second LED but, most comparators have a very small input offset voltage. I am curious if there is a way to externally adjust the input offset voltage of the comparator to fit my needs.
Additionally, I'm having trouble understanding the best comparator output option for powering an LED. I believe the term "Output Short Circuit Current" is used to describe the amount of current that the chip is able to provide at it's output. Is there a specific output type that is preferred when powering something like an LED?
Please consider the following circuit:
I plan on using a voltage reference (REF2933) rated at 3.3V as one input and the voltage across the LED as the second input. The TLV1701 will compare these two voltages and remain low until the voltage across the LED falls outside of a given range. If the voltage reference has a 2% accuracy (3.234 - 3.366V) and the voltage across the LED varies from 3.0 to 3.4V then it is possible for the comparator inputs to be 0.366V apart. I understand that the input offset voltage is used to determine when the comparator switches from high to low or low to high but, is there a way to change this value to allow more room for error?