Please help me (about Gilbert Mixer)
I am a new designer of RFIC.
I am designing Gilbert mixer recently. Now I have a question about it.
How to set the dc bias to keep the four transistors of the switch stage operating in ideal switch status?
How to judge whether the four transistors operate as ideal switch?
Thank you!
actually, the switch transistors are preferred to work in saturation region when turning on, for the noise reduction purpose
it is better to run the transient simulation to see how it behaves over time
If you apply approx. 4Vt signal to the swithing pairs, they will entry in saturation mode.But it should be applied more than this, approx 200mVp-300mVp will be enough to insert them in saturation mode.
But be careful, optimize the bias current (IT) to give you minimum noise and there are some other parameters to be optimized...
Thank you very much.
I think the transistors of the switch stage should be biased to meet VGS≈Vth.
So when LO goes positive, the transistor will be on, and when LO negative, the transistor off. Am I right?
Added after 9 minutes:
Thank u!
I have another question. After I run the transient simulation, what signals should I observe? Vgs and Vth? Id of transistors? In which saturation will the transistors operate as more ideal switches?
Thank u!
I have another question. After I run the transient simulation, what signals should I observe? Vgs and Vth? Id of transistors? In which saturation will the transistors operate as more ideal switches?