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 Wed Dec 15 15:41:45 2010, Alastair & Zach, Electronics, General, RFPD design 
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 Wed Dec 15 22:29:27 2010, Frank, Electronics, General, RFPD design
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Wed Dec 15 22:36:05 2010, Alastair, Electronics, General, RFPD design
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Thu Dec 16 03:50:33 2010, rana, Electronics, General, RFPD design: comments
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Thu Dec 16 15:27:12 2010, Alastair, Electronics, General, RFPD design: comments
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Fri Dec 17 22:07:00 2010, Alastair, Electronics, General, RFPD design: comments
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Message ID: 1224
Entry time: Thu Dec 16 15:27:12 2010
In reply to: 1221
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| Author: |
Alastair |
| Type: |
Electronics |
| Category: |
General |
| Subject: |
RFPD design: comments |
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The 4107 replacement that Rich suggests using is the LMH6624MA. It's pin for pin compatible with the 4107, which is why I hadn't changed the part on the board - I'll do that now though just to avoid confusion.
The AP1053 is a teledyne-cougar RF amp. Highlights are:
- Gain doesn't roll off till above 1GHz
- 50 ohm input and output
- Power output of 26dBm.
- This is the 10dB gain model, but it is pin for pin compatible with a whole load of others in the range so we can swap in whatever gain we want.
- Rich tells us the input will be internally AC coupled, so we don't need to do this on the board. Looking at the website and the datasheet this isn't explicitly mentioned though.
| Quote: |
- Add pads around all the voltage regulators for diodes to prevent transient spikes (e.g. preventing the 7815 output from spiking higher than its input).
- Add pads to allow more capacitors around the voltage regulators; the large caps ought to be bypasses by little ceramic caps.
- May want to add an L between the +15V and the power supply pin on the RF amp. This is sometimes done for RF amps to keep the RF out of the supply for the other guys who need +15V.
- The 4107 can develop DC offsets. Should AC couple the output going in to the RF amp.
- Add a series L-C in parallel with the R8. Sometimes we like to put a notch in the feedback of the 4107 to get extra notch action.
- Put a note on the schematic (almost obvious) that all resistors must be metal film. If any resistors require more than a 1/8W power rating, it should be indicated on the schematic.
- Since the 4107 is nearly obsolete, you ought to also scope out another amp and list it in the schematic notes as a good replacement choice.
- Put a note on there about what the hell a AP1053 is.
Otherwise, looks pretty good to me. Make sure to calculate the input-referred noise of the AD620 with the gain setting that's there to make sure you're happy with the circuit's RIN sensitivity.
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