Hello everyone,
I agree with naazira here. She is right in saying that larger the absolute negative value, better is the sensitivity. But well as far as fayiqa’s query about permissible minimum and maximum values of receiver sensitivity is concerned , i feel that it would strongly depend on the type of system you are implementing. If your requirement is detecting a particular signal then you may make your system more sensitive to that particular signal or wavelength only hence selecting more negative value and vice versa. I hope you got my point.
Regards