you say you need more amplitude and yet the numbers you are quoting are all frequencies. you will need to explain more clearly what you need.
amplitude is the difference in voltage between the high and low states of the square wave. frequency is the rate at which pulses of the square wave occur.
since I don't imagine a 555 would be outputting only 0.5v p-p signals, I assume you meant frequency.
the frequency of the 555 output is entirely dependent on the resistors and capacitors you attach to it. if you do a search at google you can very easily find information about component selection for 555 output frequencies.
okay, how many threads do you have going for this exact same topic? this is at least the second one that I have seen. it is very bad etiquette on a forum.
if you're not getting the response you were hoping for in the first thread, tough. Making more threads to try to get more attention is just rude, and wastes more of everyone's time.
LM555 won't handle the supply voltage you need. LM741 does not have adequate slew rate. Below is a square wave generator using an LM318, which solves both problems.