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TRF37A75: Unexpected Increased current consumption

Part Number: TRF37A75
Other Parts Discussed in Thread: TRF37B73


Our customer is using the TRF37A75 and TRF37B73 devices in their system and they are testing their prototype. The following concern was raised


I am currently designing a number of RF Amplifiers based on TRF37A75 and TRF37B73. During testing I've found 2 cases one TRF37A75 and one TRF37B73 that showed after some time an increased supply current of 2 to 3 times the normal amount. In both cases the gain and compression was still more or less unchanged and they functioned as normal.

In first case I wasn't sure if I've had the device damaged mechanically (PCB flexing) and I've replaced it. Now a second case has come up. In this case the current started to float up and after a while settled back to normal, again it functioned "normal" and I could not notice any wild oscillation.

However, in both cases I've had relative small input/output coupling caps of 2.7pF for a 4.7 GHz application, otherwise the supply circuit as per application note.

Am I doing something wrong?

Do they need a higher input capacity (1nF) to stabilize the active bias?

Are there any further information available, such as a internal block diagram ?

The point is that I am getting a bit concerned as we've got about 10 of these devices in our new design and I don't want to get caught with production issues.


Thanks very much

Faizul Bacchus


  • Hi Faizul,

    I don't think the input/output coupling caps of 2.7pF should be responsible for the abnormal behavior of the supply current. They could try using a higher input capacitor to see if the issue goes away.

    Do you know what device (LDO or switcher) is providing supplies to the TRF37A75? Also, is the supply power up to the TRF37A75 Vcc pin and the output bias inductor occuring at the same time? Also, how is the customer measuring the current of the TRF37A75 device?

    Best Regards,
  • Hi Rohit

    Thanks for your response. I have forwarded your reply to the customer and asked them to reply with the information. I don't have the schematic.

    Thanks very much


  • Hi Faizul

    Can you ask the customer what value they are using for their choke inductor? The devices was design with an optimal stability point using 100nH Coilcraft RF choke. Other values could potentially cause an instability that would result in oscillation and increased current. I would also suggest they use a small loop antenna connected to a spectrum analyzer to try and look for any oscillation.