DAC vs gate pin of FET + is there any programmable charge pump IC to control the VCO?

I can't find any programmable charge pump IC, i google for "programmable charge pump". Only some LED drivers and USB +5/+10 charge pump.
The other alternatives i see is DAC + Op-amp (but why op-amp is needed if we only need to make a little bias?). I am interested in charge pump after reading some datasheets on Frequency Synthesizers with integrated charge pumps, etc.. They are nice chips, but much more than i need.

Actually i tried to connect gate pin of FET transistor to DAC output (i know, it's lame). Can something wrong happen to DAC in that case?
Gate pin had biasing resistor, so i removed resistor and connected gate pin to the 12-bit DAC. Suprisingly it worked, but i am not totally sure it is ok:
- In the first case biasing resistor provides some bias and results in some operating curve of FET.
- In the second case DAC provides bias, and it seems ok to use. Is anything wrong with my theory?

The charge pumps are not programmable current outputs in PLL circuits.They are just simple current sources triggered by UP or DOWN pulses which are coming from PFD.
Their currents are in SINKING or SOURCING mode just like 2 current sources are connected series with a common output/input.
Implemention is quite easy, all you need a stable voltage reference.You may find many docs. on the internet and you can do it with few transistors.