I am simulating a LNA which is of differential topology . I want to find its single ended gain and Band width. Mainly I want to know what is the maximum operating frequency.
What do u mean by maximum operating frequency. If you say that the band limitation of your LNA, this will be determined by the ft of your transistors. Therefore you have to bias your transistors at such operating points that will yield max. ft. Also you have to conside NF and power consumption.
The maxim operating frequency of an LNA is given by the RF system analysis.
Is the frequency limit where the LNA has acceptable gain (generally > 10dB) and maximum noise figure (generally <2dB, but imposed by the RF system analysis to get the proper SNR)