I want to know that what is the range of the voltage supply required for 7 segment display??
LT542 is the one that I am using for my project.
a,b,c,d,e,f,g comes out from 4026 Ic.
Need all your assistance as soon as possible.

 

It is not the voltage you should be concerned about, it is the current.

 

Just assume that the current passing through each segment should not exceed 20mA. Normally, you can use a single resistor for each display, on the common pin. Alternatively you can use a resistor per segment, if you are concerned about having a constant brightness for all numbers displayed.

 

Actually, you need a separate resistor for each segment. Otherwise, the current per segment (and thus the brightness) will vary based on how many segments are on.

The voltage drop for an LED display will depend on the color (about 1.1v for red, 1.7v for green) and for larger displays, how many LEDs are in series for each segment. You can use this voltage as well as the output voltage of your driver and the desired current to figure out the value of the current-limiting resistor.
/mike