Hi Raghu,
Attaining a 16 bit Digital to Analog Converter (DAC) is usually done with resistors hooked in a R2R method. The following company sells an integrated circuit which can be used to hook 16 bit DAC.
http://www.semiconwell.com/r_net/swr2r16.htm
SEMICONWELL
Integrated Passive Networks 16 BITS R2R RESISTOR LADDER NETWORK
Regards,
Charles Bannister
SWR2R-16 (20 pin DIP)



R2R ladder network is one of the most commonly, simple and inexpensive way to perform digital to analog conversion, using repetitive arrangements of precision resistor networks in a ladder-like configuration. This style resistor network is ideal for digital to analog (D/A)and analog to digital (A/D) conversion. The use of an R-2R ladder architecture is very useful for binary-weighted currents, the R-2R based D/A, A/D converter is easy to implement and the resistance ratio is independent of the number of bits, only the precision of the resistor is significant. Because the resistance of the R2R architecture must be so closely matched (as close as 0.01% for the LSB on an 8-bit DAC) and the current ratio through the switches is still large the implementation of current sources is needed. With equal current flow through all the switches the architecture will be slower but more stable.