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Hi FvM,
Just got a reply from Rogers. They have guaranteed that there would be no issue during reflow processing as this is usually done for a couple of minutes.
Thanks for the help.
Hi FvM,
Thanks for the quick reply. What material would you suggest that would make a great combination with RO4003C? We have already put this question to Rogers. I think if we take care of the thermal expansion coefficients of the hybrid materials to be similar, there shouldn't be an issue.
Hi all,
We are trying to make a 4-layer PCB for 5.8 GHz power amplifier application. The circuit has been verified on a two layer board, but to take care of better connectorization, we are going for 4 layer board.
Here we want to have the following stackup:
+ Top layer and Mid layer1 from...
Hi all,
I feel oscillation is the problem. We had designed the operating band to be from 5.7 GHz to 5.9 GHz. It so happened during tuning the circuit that the lower end frequencies are oscillating. We could observe positive S11 in the lower frequency bands over a very wide band.
When...
Hi all,
It looks like the device is damaged. There is a reason for this. Due to a wrong choice of an output DC blocking capacitor, the circuit was getting into oscillations. This was revealed during simulations. Could such oscillations prove harmful to transistors?
Any thoughts?
Hi albbg,
We are presently using the same method suggested by you to probe the various points on the board. We are doing this by soldering the cable shield to the GND of the PCB.
Added after 4 minutes:
Yes Biff, I am also now doubting the device.
Let me check the input output matching...
Hi Biff44,
When we change the Gate bias, the drain current is getting varied accordingly. But the RF output is 22 dB below the required.
When we operated the device at about 6x the actual operating current, we had found that touching the heat sink (not the device) used to burn our fingers.
If...
Hi,
Thank you very much for your suggestions.
Good question. Please find the answers to your queries below:
We have simulated the amplifier and the S11 (-8 dB) and S22 (-12 dB) are better in simulations. The reference design in datasheet shows S22 of -3 dB.
The output power is 30 dBm, Gain is...
Thank you, albbg
Let me test further, first the discrete components if there is any problem with them. If this doesn't work, let me replace the transistor.
Hi,
Have any of you used GaN transistors?
We are using a GaN pHEMT. This transistor was operated at a power well above the maximum for about an hour by mistake. This was realized later and subsequently the bias was adjusted to bring down the drain current. Initially for a while the transistor...
Hi gentlemen,
Can anyone tell me if there is any issue in going ahead with a RL of -3 dB provided output power is optimized? What will be the consequences of such an approach?
Hi,
Thanks for the comments.
Big Boss:
Infact as you pointed out, S11 is a lot better compared to S22.
My next question is that is there any problem living with this value of S22? Please help me understand this. We are a bit reluctant to use isolators and balanced circuit due to cost...
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