Circuits
Junior Member level 2
Hello all,
I am designing a low noise amplifier for low power applications. I have a question.
I know we usually use SP analysis to measure the performance of the LNA which tells us about gain, reverse isolation, input reflection etc.
The problem is , I get different values of gain from noise analysis, ac analysis and sp analysis. The gain from ac analysis and noise analysis matches but S21 is completely different. I should get a high gain but with sp analysis I get 10dB difference from transfer function from other analysis.
How do we set the output port ? I do not want to set it to 50 ohms because my next stage is going to be a NMOS transistor. As I understand , the input resistance of the NMOS is very very high, so I am setting my port resistance around 2k. But this still does not help me in getting higher gain:-?. I know that the gain depends on the input resistance of the next stage but if the input resistance of the next stage is very high then we will have gain equal to intrinsic gain ( approximately ). I am very confused because my gain is very low which I think is not right.
Any suggestions?
Please advise.
Thanks
I am designing a low noise amplifier for low power applications. I have a question.
I know we usually use SP analysis to measure the performance of the LNA which tells us about gain, reverse isolation, input reflection etc.
The problem is , I get different values of gain from noise analysis, ac analysis and sp analysis. The gain from ac analysis and noise analysis matches but S21 is completely different. I should get a high gain but with sp analysis I get 10dB difference from transfer function from other analysis.
How do we set the output port ? I do not want to set it to 50 ohms because my next stage is going to be a NMOS transistor. As I understand , the input resistance of the NMOS is very very high, so I am setting my port resistance around 2k. But this still does not help me in getting higher gain:-?. I know that the gain depends on the input resistance of the next stage but if the input resistance of the next stage is very high then we will have gain equal to intrinsic gain ( approximately ). I am very confused because my gain is very low which I think is not right.
Any suggestions?
Please advise.
Thanks
