differential output low noise amplifier designed with cadenc

[macg84]

Hello,
I have attached the differntial output of my LNA, i used an AC analysis with sweep range start 1G stop 3G, e sweep type logarithmic with 10 points per decade. In imput there is a PORT with AC magnitude equal to 1. This LNA has to work at 1.8GHz, is this output correct???

 

[Mazz]

There are few mistakes in this schematic:

1. you are driving the amp with zero ohm source impedance. If you use a port, I suppose you want to drive it with 50 Ohm source impedance, but the way you make it differential makes it zero.

2. is not clear how you measure the gain. why not taking at positive net of PORT3?

I hope it can help

Mazz

 

[macg84]

Re: differential output low noise amplifier designed with ca

Thank you very muh Mazz ...!!! But I have to mesure the differential output, so I have to take the positive and negative output between 1 and 2 (like in schematic2)???? and why there is a generator VCVS in the output of port 3 with gain 1, what is its function in this circuit ???

 

[Mazz]

It's really strange that you are asking details about a schematic that you have posted!

anyway, the vcvs makes simply the difference between the two output voltages, that is, by definition, the differentail output. Please note that node 2 is GND.

Mazz

 

[macg84]

Re: differential output low noise amplifier designed with ca

To misure the output caracteristic of a LNA in cadence we can use Spectre and sp analysis, hence choose sp anlysis, then you have to choose the input and output port of LNA ande the frequency range for the correct analysis and then you can run the simulation. After the simulation you can gon in direct plot-sp analysis ad choos your favourite parameter (s11,s21,s12,s22)...