I wrote:
The LT1720** works on a 3.3v single supply, and has internal
hysteresis. Just ground one input, ground the other through a
resistor, and attach your AC-coupled signal (best if you can use
equal resistors to ground on the two inputs, but if the signal
termination is 50 ohms the other input can be 0 ohms to ground; even
1k ohm would probably be OK).
Note that the LT1720 is specified for inputs to 100mV below V-
(ground, in this case) and your 200mVpp signal pushes it right to
the limit. A bit of attenuation is probably a good idea.
** The 1720 is a dual comparator, so you'd have an extra to use or
ignore. Alternatively, the 1719 is a single with extra features
that you could ignore. Either should work well in your application.
The TLV3501 from TI may be an even better choice. It has almost
exactly the same amount of internal hysteresis as the LT1720/1719
(which I am convinced is largely responsible for the friendly
performance of the LT parts, along with the right amount and internal
distribution of gain and freedom from internal thermal
feedback). Its input range also extends to 200mV below V-, twice as
far as the LT parts, and it is a single (TLV3502 is the dual). Its
input leakage current is vanishingly small, so unequal resistances at
the inputs will not shift the trip point. Finally, it is available
in the smaller SOT23 package (as is the LT1719).
Potentially, lots to like. I have not used the TI part, so I don't
know if it is as friendly to apply as the LTs, but others speak well of it.
Best regards,
Charles
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