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HMC981 test circuit

Question asked by BenvdBergh on Jun 9, 2015
Latest reply on Jun 11, 2015 by kkaya

Dear Sir/Madam, community members.

Could you please comment on the following?

Background

We are currently using a HMC981LP3E to bias a HMC465LP5

Vdrain = 8V @ 160mA

-Vg1 =0 to -2.5V

+Vg2 = 1.5V

 

We are using two linear regulators to supply VDD at 8.8V and VDIG at 3.3V

Please see circuit below:

Questions:

1) Could you please suggest a "load circuit" that could be used to test the function of the HMC981 in the absence of an HMC456?

2) We measure a voltage of 7.93V on the VDIG pin, this seems to be coming from the VDIG pin even though one would expect his to be a input pin.(the 3.3V regulator works fine but being a series pass device it has no means to "pull" an too high voltage on its output low.)

 

Thank you

Regards

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