on-chip LNA output match to 50 ohms, what's the trick?
时间:04-09
整理:3721RD
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Okay, so I figured out how to measure noise figure in pSpice, it was simple as I suspected. There is one sticky point left to my LNA design, the output match at 2.45GHz
I am supposed to use bond wires and on chip capacitors only to create the output match to 50Ω. My LNA is a cascoded mosfet design. I have an inductor in the drain to resonate out the Cgs of the cascode device. I can get some very high output resistances with this ~7kΩ if I try, but then I have to match that to 50Ω. Won't this Ro be quite variable and make it hard to impedance match?
I'd like to just be able to put a bond wire inductor from LNA output to 50Ω load and make an L-match, but this ends up loading the nice resonanant cancellation I have in the drain and changing its resonant frequency. If this were any other design I'd stick a buffer between the two and call it a day, but that increases the noise figure.
What can I do?
I am supposed to use bond wires and on chip capacitors only to create the output match to 50Ω. My LNA is a cascoded mosfet design. I have an inductor in the drain to resonate out the Cgs of the cascode device. I can get some very high output resistances with this ~7kΩ if I try, but then I have to match that to 50Ω. Won't this Ro be quite variable and make it hard to impedance match?
I'd like to just be able to put a bond wire inductor from LNA output to 50Ω load and make an L-match, but this ends up loading the nice resonanant cancellation I have in the drain and changing its resonant frequency. If this were any other design I'd stick a buffer between the two and call it a day, but that increases the noise figure.
What can I do?
I figured it out, I used an on-chip tapped capacitor, stepping down to the load resistance of 50 ohms
you can try to use a output buffer stage to match the output to 50 ohm.
