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Old 27th June 2012, 03:41 AM   #21
quanghao is offline quanghao  Viet Nam
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Quote:
Originally Posted by keantoken View Post
Quanghao, the input stage to the OPA6x7 is not a conventional LTP. Notice the phase is actually reversed; the Jfet sources actually point up; they are P-channel. This could give nice advantages to the way compensation is applied.

There are ways to perform this phase reversal with an N-channel or NPN LTP (something like cross-comp) but I think these may cause stability problems.

It would be interesting to see if you can make it work with the same input topology as the OP6x7. Otherwise, the circuit is actually pretty conventional, if performing well.
I TEST ALL , thanks
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Old 27th June 2012, 03:59 AM   #22
keantoken is offline keantoken  United States
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Quanghaou, none of those were the circuit used in the OPA6x7. This is the proper internal schematic. Operating points and transistors were guessed.

Again, notice the LTP is P-CHANNEL. It will not work if you remove Q1, 2, 3, 4 or 6. The input stage is the only thing, based on the datasheet schematic, that makes this opamp unconventional. Else it's just an ordinary opamp.

With discrete components, the amp should probably be converted to use the complementary parts since N-channel Jfets and bipolars will perform better.
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Old 27th June 2012, 04:02 AM   #23
quanghao is offline quanghao  Viet Nam
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The voltage amplification, i can test
thanks
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Old 27th June 2012, 04:04 AM   #24
quanghao is offline quanghao  Viet Nam
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Quote:
Originally Posted by keantoken View Post
Quanghaou, none of those were the circuit used in the OPA6x7. This is the proper internal schematic. Operating points and transistors were guessed.

Again, notice the LTP is P-CHANNEL. It will not work if you remove Q1, 2, 3, 4 or 6. The input stage is the only thing, based on the datasheet schematic, that makes this opamp unconventional. Else it's just an ordinary opamp.

With discrete components, the amp should probably be converted to use the complementary parts since N-channel Jfets and bipolars will perform better.
I love your comments!
very useful, thank you very much, I do not know how to use the software you are using!
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Old 27th June 2012, 04:07 AM   #25
quanghao is offline quanghao  Viet Nam
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Quote:
Originally Posted by keantoken View Post
Quanghaou, none of those were the circuit used in the OPA6x7. This is the proper internal schematic. Operating points and transistors were guessed.

Again, notice the LTP is P-CHANNEL. It will not work if you remove Q1, 2, 3, 4 or 6. The input stage is the only thing, based on the datasheet schematic, that makes this opamp unconventional. Else it's just an ordinary opamp.

With discrete components, the amp should probably be converted to use the complementary parts since N-channel Jfets and bipolars will perform better.
Hi! can you sent help me the file in LTSpice

thanks you hepl!
Quanghao
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Old 27th June 2012, 04:34 AM   #26
keantoken is offline keantoken  United States
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Here is the simulation file. C4 and C5 have nothing to do with the actual OPA6x7; the high input capacitance of the J109 makes them necessary. I did not take much time to try and choose an appropriate input jfet.
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Old 27th June 2012, 04:38 AM   #27
quanghao is offline quanghao  Viet Nam
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Quote:
Originally Posted by keantoken View Post
Here is the simulation file. C4 and C5 have nothing to do with the actual OPA6x7; the high input capacitance of the J109 makes them necessary. I did not take much time to try and choose an appropriate input jfet.
ok i can Test in the Mutisim
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Old 27th June 2012, 08:12 AM   #28
quanghao is offline quanghao  Viet Nam
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[QUOTE=Jay;3072881]

Is it a big improvement soundwise?
Yes, i like it!
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Old 27th June 2012, 08:13 AM   #29
quanghao is offline quanghao  Viet Nam
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I'm almost to 637, and is much improved than in the constant current
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Old 27th June 2012, 08:29 AM   #30
quanghao is offline quanghao  Viet Nam
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AND this circuit!
i think it is ok for me!
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