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HMC659LC5 RFIN DC block cap ?

Category: Datasheet/Specs
Product Number: HMC659LC5

Hi all,

In the datasheet @ HMC659LC5,

RFIN : This pad is DC coupled and matched to 50 Ohms.

And there is no DC blocking capacitor at RFIN in the application circuit.

Are DC blocking capacitors really unnecessary?

Best regards,


  • The application circuit does need an external dc-blocking capacitor but this capacitor was left off of the eval board to afford maximum evaluation flexibility. So for folks who want to go down to a very low frequency, they can use a large cap but that my cost them bandwidth at the top end of the frequency range. For bench evaluation with the evaluation board, I would suggest that you get a coaxial dc block.