LNA Predistorsion
LNA Predistorsion
(OP)
Hi,
I´m designing a LNA for an FM receiver. I need 60dB of IMR3 due to customer requirement. In order to achieve that high req. I used a diode in the input of the amplifier as a predistorsion method. It really works for intermodulation, but I have doubts about noise. Does anyone know if this is a good solution? What is the impact on noise of this diode in the input of the amplifier?
Thanks!
I´m designing a LNA for an FM receiver. I need 60dB of IMR3 due to customer requirement. In order to achieve that high req. I used a diode in the input of the amplifier as a predistorsion method. It really works for intermodulation, but I have doubts about noise. Does anyone know if this is a good solution? What is the impact on noise of this diode in the input of the amplifier?
Thanks!





RE: LNA Predistorsion
I have hear of using the same transistor as a diod and running the same bias through it and thermally connecting the devices to get some semblance of match. But a match to cancle below 60 dB level sounds like an uberEngineer job.
Good luck. I will monitor this thread for reports of your success and advice of others. This should be interesting.
Merry Christmas.
jsolar
RE: LNA Predistorsion
I guess the answer to your question revolves around what the diode dynamic resistance is. If you are biasing it up so it only has an ohm or two of resistance, then it will probably not screw up the NF. If it is acting like a 200 ohm resistor, forget about calling it a LNA!