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Design >> RF Design >> How to bias a Passive mixer ?
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Message started by Muhammed on Jun 13^th, 2012, 5:41am

Title: How to bias a Passive mixer ?
Post by Muhammed on Jun 13^th, 2012, 5:41am

Hello all .. i want to ask about biasing Passive mixer just 4 MOS as switches .. but i want to set the Dc Output Common mode .. for them ... any idea how can i do this without large flicker noise due to dc bias

thanks

Title: Re: How to bias a Passive mixer ?
Post by vivarf on Aug 2^nd, 2012, 5:12am

This might relates to quite complicated analysis you can find in many published work in IEEE. For simple design you want to bias Vgs=Vth to minimize flicker noise.

Title: Re: How to bias a Passive mixer ?
Post by RFICDUDE on Aug 4^th, 2012, 5:12am

I suppose you could use a resistor divider from a power supply to set the common mode to some fraction of the supply. This voltage will obviously track supply changes and also potentially let noise on the supply couple to the mixers, but it is simple. The gate bias would need to be supply referenced too such that the overdrive on the switches doesn't vary with supply.