Re: what is the difference between postive and negative volt
Voltage is allways measured between two point. If only one is given, the other is assumed to be ground ( 0 volts reference ). Positive or negative at last is a convention.
Probably by "positive voltage IC" you are referring to a Voltage regulator IC.
For example, you have:
Three terminal positive voltage regulators as the 7805 and three terminal negative regulators as the 7905.
Use of one or the other depends on the application.
If you are refering to other ICs please clarify.