Prabhu
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I am designing a double balanced Gilbert cell with current bleeding to increase the conversion gain and to reduce flicker noise, to use smaller switches .
My problem is this:
Every one says that linearity of a Gilbert cell is primarily determined by the linearity of the transconductor. In my design, the transconductor alone has IIP3 = -10 dBm. Overdrive of the switches = 50 mV, LO drive = 0.2 V peak single ended. I_bleeding = 0.5 * I_transconductor. But my mixer IIP3 = -18 dBm. If the switches switch properly, they should not affect the linearity. What could be the reason for this IIP3 degradation?
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