Help me find a frequency multiplier IC

i need an ic which multiply input frequency by 1000 on output , input frequency ranges from 2KHz to 12 KHz

I would say you could use a PLL, but the input frequency range is very low. Can you explain a bit more what you need to do?

If you want to approximately multiply by 1000, you can convert the frequency to a voltage using a frequency-to-voltage converter circuit, and then you can drive a tuning port on a voltage controlled oscillator.

If you need exactly x1000, use a PLL circuit, with the PLL loop filter sized accoriding to the dynamic characteristics of what you are locking it to.

You will not find IC to multiply 1000x of your input frequency. The maximum multipling factor available in IC form will be upto 4x only.
For your application you need only 12 MHz. So go for VCO ICs. It will vary the frequency w.r.t. your input voltage. VCOs will produce upto 2GHz.

there are some methods:
1. You can amplify you signal to push a transsitor to saturated status, then there should be some harmonics, you can filter the 10th harmonics; then double do so to get X1000.
2. You can push a pair diode to get odd harmonics, say X15. Then more stages.