ikalogic
Member
Helloes!
So, here is the situation: I have one sensitive IC, powered in 5V. In one mode i want that sensitive IC to be connected to real world, and act as a digital generator (generate say 0/5V TTL signals)
In another mode, i want this sensitive IC to be isolated, and be safe, even if on the "outside world" pin, the voltage goes up to 24V or down to -24V.
I am thinking of using the circuit below, where i would activate both BJTs to connect the pin to outside world, and turn them off to isolate the pin..
I am afraid this will most likely kill the BJTs right..?
I would have used simple resistors and zeners, but the problem is when generating the TTL signals, i don't want them in the way..
The ideal solution would be a good old relay, but it's too bulk, expensive, power hungry and unreliable...
can any one comment on my basic idea? would this work? if not (which i think is the case) what would be the best way to do it?
Thanks a lot![Smile :) :)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)
So, here is the situation: I have one sensitive IC, powered in 5V. In one mode i want that sensitive IC to be connected to real world, and act as a digital generator (generate say 0/5V TTL signals)
In another mode, i want this sensitive IC to be isolated, and be safe, even if on the "outside world" pin, the voltage goes up to 24V or down to -24V.
I am thinking of using the circuit below, where i would activate both BJTs to connect the pin to outside world, and turn them off to isolate the pin..
I am afraid this will most likely kill the BJTs right..?
I would have used simple resistors and zeners, but the problem is when generating the TTL signals, i don't want them in the way..
The ideal solution would be a good old relay, but it's too bulk, expensive, power hungry and unreliable...
can any one comment on my basic idea? would this work? if not (which i think is the case) what would be the best way to do it?
Thanks a lot