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Design >> RF Design >> MOS parallel to antenna - antenna clamp, antenna modulator
https://designers-guide.org/forum/YaBB.pl?num=1448980511

Message started by Tako on Dec 1^st, 2015, 6:35am

Title: MOS parallel to antenna - antenna clamp, antenna modulator
Post by Tako on Dec 1^st, 2015, 6:35am

Hi,

I would like to understand the following thing: in RFID passive circuits there are MOS transistors, which work as a clamp or a modulator. These transistors are in parallel to antenna. Drain is connected to one end of the antenna and source is connected to the other end. The example can be found here:

http://i.stack.imgur.com/j8EGx.jpg

The question is: where is the body of the MOS transistor connected?

Nodes on the antenna, change voltage values. Once there is a positive voltage on "Data In" node (node 2) and negative on node 3 and after that node 2 is negative and node 3 positive. If the transistor source was connected to the body, for the situation where node 3 is positive and node 2 negative, the body-drain diode would turn on. Is that the behavior we would like to observe?