Designing a 1250-1950 MHz LNA with a dual gate MOSFET
I need to design LNA folowwing a few parameters:
Freq 1250-1950MHz
NF 1dB
Gain 10 to 15dB
And the most important parameter is I needed variable gain!
So i deceided to implement this with DUAL GATE MOSFET,
So please I need some papers or recommendations about it!
David
Any designkit offers model for dual gate MOSFET?
The data sheet should give you all of the clues. Put the signal on the gate closest to the source. Vary the voltage on the other gate to change the gm.
One good aspect of dual gate FETs is that the S12 parameter is very low which eliminates many stability problems. The bad part is that these devices are rare these days.
Which DUAL GATE MOSFET are you planning to use (type, manufacturer)?
you can get the spice model from the manufacturer. for example http://www.rfoe.net/ZILIAOXIAZAI/PHI...ata/BF901.html
you can then import it into the simulator.
Often when you inspect the model of a dual-gate closer you will see that it's nothing else but a cascode. But as both transistors are on the same die and are packaged together, of course this results in much better performance than two single discrete fets in cascode configuration.
For discrete FETs, you can measure the s-params and use them in simulations.
For on-chip, most foundries only provide models for nMOSFET. Dual gate MOSFET is not exactly the same as a cascode.
I think you will find no discrete dual-gate MOSFET for such a frequencies. Available fets are usable up to 1GHz. You should try a cascode configuration as suggested.