How??????????? Man, mine is; i want to trigger a relay using an npn transistor when there is a 5v on the comparator output. what type of relay do i have to use, transistor type because the relay will have to switch a high voltage transformer. thanks. Colin
You would use a circuit similar to the one posted above. First you need to know your relay coil current / voltage needs. Then with that known you can worry about selecting a transistor that will drive that load (relay coil). You really need to provide more information. Also define "high voltage" that the relay will be switching. Also, the current load the relay will be switching.