DHCP Server to give out more than 250 IP addresses on the same network

Hi,

  When we have a WIndows server with DHCP server running, you can make it to give out IP addresses to computers on the network.  Say from 192.168.1.20-250.
  But if your network has, let's say, 350 desktops, 50 network printers and 250 IP phones, somehow you need to make DHCP server give out 650 IP addresses and you wan them to be on the same IP network.
  How do you accomplish that?

Thanks.