I want to use a T/R switch IC to select the filters. So I made a small board test HMC784AMS8GE IC like the schematic below:

enter image description here

The input (IN1) is the sine signal. But when I test, both OUT1 & OUT2 have the same signal as IN1 and both outputs (RF1, RF2) are always ON. Although, I changed the Control pin (A, B) following the datasheet. It means the RF switch inside the IC did not work properly when adjusting the value of the control inputs(A, B). Could you help me to solve this problem? Thank all guys.

  • $\begingroup$ R1, 2, 3 & 4 are short-circuiting the 5 V supply. Are you removing two of them to make the selection? $\endgroup$
    – Transistor
    Jul 23, 2020 at 7:53
  • $\begingroup$ Yes. I use resistors to select logic values for IC. I do not use( R1 & R3) or (R2 & R3) at the same time. $\endgroup$ Jul 25, 2020 at 8:00

1 Answer 1


Per the datasheet "RF1 and RF2 are reflective shorts when “OFF”". For best results consider the following configuration.

enter image description here

Also per the datasheet below is the suggested interface for logic signal A and B

enter image description here

I suggest try using TTL logic to drive the logic signals



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