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Very Low-Capacitance LF Switches


Our design uses electronic keys for switching very weak and relatively low frequency currents. And it is very important that its capacitance Coff (source/drain; RFx/ RFC) would be 0,1...0,2 pF, range begin with 0 Hz (DC)… to a few kHz, and it would have low charge injection.

I am currently using MOS FET Relays and going to try MEMS RF Switches (probably ADGM1304). But maybe there are ‘simple’ RF switches suitable, e.g. HMC or ADG series? I tried ADG1211 but its off capacitance is more than necessary (1pF).

I will appreciate your advice.




  • Hi Andrew,

    The ADG12xx series are our lowest capacitance and charge injection precision (DC + lower frequency) industrial range switches (i.e. +/-15V).  They are class leading. Note the capacitance is measured at the pin relative to ground.  The package pin capacitance itself is a large part of the value.  Its hard to get lower for that reason. In a lot of applications the pin capacitance can be calibrated out. 

    The ADGM1304 has similar off capacitance, coming from the LFCSP package.  The actual capacitance of the MEMS off switch unit itself is very small. 

    Another part worth looking at is the ADG901, its a small package low capacitance RF switch.  


  • Hi Eric,

    Thank you for such a detailed answer!