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Old 16th August 2010, 05:31 PM   #61
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Old 17th August 2010, 01:22 PM   #62
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I received my matched Jfets today from Spencer. I have 8 x 7.4mA and 4 x 6.6 - 6.7mA.

I understand that it's preferable to have the two inner jfets of the group with slightly lower idss. So is it better to have four perfectly matched at 7.4mA or use the 6.6 - 6.7mA for the inner two like this:

7.4 - 6.7 - 6.7 - 7.4

Is there any harm (dc offset?) to have all four the same idss?
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Old 17th August 2010, 01:28 PM   #63
Salas is offline Salas  Greece
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Perfectly matched is best for offset and won't be pushing each other also. The pairs you proposed are not slightly different, they are clear non matches. When I say use the slightly lower one for inner position, I mean slight differences between a matched pair beyond the decimal point.
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Old 17th August 2010, 01:36 PM   #64
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And use a jumper instead of any 600R where it says note.
I just want to make sure, don't want to fry anything.

What is the purpose of J1, under what conditions would a jumper wire not be installed?
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Old 17th August 2010, 02:20 PM   #65
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To be clear - there is NEVER an instance when J1 is not connected. There is a permanent connection there anyway, even without a jumper wire being added. If you scratch away a little at the white paint on the top of the board, you will see that J1 already has a copper trace in place. Adding a jumper wire there only re-enforces that connection.
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Old 17th August 2010, 02:30 PM   #66
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Then why is the jumper there?

What are the 3 holes next to the V+ (10) G (20) V-(30) used for?
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Old 17th August 2010, 02:41 PM   #67
Salas is offline Salas  Greece
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Because Crt that made the board layout wanted to reinforce the ground better.
Just install whatever the board depicts, and do as it notes. You will be OK.

If you mean those 3 to the right before the audio section, are to install a connector for someone that wants to tap off the reg or just use it as a standalone reg for other circuits.
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Old 17th August 2010, 03:02 PM   #68
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Perfectly matched is best for offset and won't be pushing each other also. The pairs you proposed are not slightly different, they are clear non matches. When I say use the slightly lower one for inner position, I mean slight differences between a matched pair beyond the decimal point.
OK Salas, four matched it is then. Many thanks
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Old 17th August 2010, 03:05 PM   #69
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Originally Posted by Salas View Post
Because Crt that made the board layout wanted to reinforce the ground better.
Just install whatever the board depicts, and do as it notes. You will be OK.

If you mean those 3 to the right before the audio section, are to install a connector for someone that wants to tap off the reg or just use it as a standalone reg for other circuits.

Thank you.
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Old 18th August 2010, 08:12 AM   #70
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On my search to find the best parts, i found an interesting alternative to the recommended MUR820 rectifier diode:

Qspeed LQA08TC600

It has a 68% faster reverse recovery time (11ns)! Any comments about this part?

For smaller currents you get it also as LQA03TC600 (3A - 9,3ns) and LQA05TC600 (5A - 11ns)


Best regards,
Oliver
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