FAQ: AD8340, AD8341, and ADL5390 Vector Modulators: IBBP, IBBM, QBBP, and QBBM Input Impedance to Ground

Document created by Larry Employee on Oct 28, 2009Last modified by AndyR on Jan 31, 2012
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Q.

What is the input impedance to ground for the I and Q inputs of the AD8340, AD8341 and ADL5390 vector Modulators?

 

A.

These inputs connect to the bases of transistors. So the input impedance will be high and will consist of a resistive and capacitive component. Simulations show an impedance of about 23 megaohms in parallel with approximately 400 fF of capacitance from each input to ground.

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