Hello,
I am designing a CMOS receiver circuit. I have a few doubts regarding the LNA and mixer design.
1. In LNA design usually the cascode transistor's width is kept equal to the main transistor's width. this is done so that the source of the cascode transistor and the drain of the main transistor can be merged into one, which reduces the noise of the cascode transistor due to its source to substrate capacitance. Also we use fingering to reduce the effect of gate resistance. If we use fingering then we cannot merge the source of the cascode transistor with the drain of the main transistor and the reason for which we make the two widths same is no longer valid. In such a situation how do we determine the width of the cascode transistor so that the noise figure is kept minimum and gain is high.
2. Are there any good links to the design of double balanced gilbert cell mixer. Most of the papers that I could find give only the working and not the designing of the mixer.
Thanks for your help
Rittu