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How to improve Linearity of Wideband LNA?

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dopradar

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Hi all,

Recently I am tunning a LNA, which should work at 50-900MHz.Now gain and VSWR are ok.I have set high bias-point and Emitter series with inductor to improve IIP3. but IIP3 is only -4dBm at 50MHz, 3dBm at 600MHz and 6dBm at 860MHz. So how to improve it?

and another method to improve IP3 is make a tradeoff between Gain and Linearity,but how to realize it? Does decreasing gain mean IP3 improving undoubtedly ?

Thanks!
B&R
 

The 10 dB return loss "rule of thumb" is sometimes violated to achieve better noise figure or IP3 in RF amplifier design. Lower gain also it will improve IP3.
 

I think some feedback mechanism could be introduced in this case
 

1. what is IP3 goal you wish?

2. from your current IP3 figures I guess your LNA gain is not quite flat. I suggest you could add R-C feedback betwen base and collector instead of at emitter

3. for IP3 performance, you could try increasing LNA supply voltage (or voltage Vce)
and push bias current to limit
 

Thank you for your suggestion!

Hi sunn,

My IIP3 target is 10dB at all frequency band.and I will have a try to connect RC between base and collector.
 

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