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Old 26th January 2013, 09:29 AM   #1
scafas is offline scafas  Italy
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Default new discrete opamp for line preamplifier

Hello everyone, I built this operational transistor and let me know which circuit and 'suitable to build a line-stage preamplifier.
must be supplied with dual voltage and the more 'simple as possible.
I tried to replace it with a NE5532 and I can say that it works very well but I would like a circuit that uses all its potential
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it's use bc550c /bc560c and bd135-bd136
tks
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Old 26th January 2013, 11:36 AM   #2
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This topology gives excellent results (it's similar to the Jensen JE990, but complimetary) - a few improvements are possible:

1) A current mirror on the LTP helps increase loop gain as well as equalize input offsets at the LTP.

2) Instead of a Darlington VAS, and emitter-follower driving a common-emitter VAS gives better results with the same number of transistors.

3) The Miller compensation may be referenced to the output (Cherry compensation), rather than the collector of the VAS, and helps reduce distortion of the output stage also.
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Old 26th January 2013, 08:39 PM   #3
scafas is offline scafas  Italy
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Default opamp jensen

Quote:
Originally Posted by linuxguru View Post
This topology gives excellent results (it's similar to the Jensen JE990, but complimetary) - a few improvements are possible:

1) A current mirror on the LTP helps increase loop gain as well as equalize input offsets at the LTP.

2) Instead of a Darlington VAS, and emitter-follower driving a common-emitter VAS gives better results with the same number of transistors.

3) The Miller compensation may be referenced to the output (Cherry compensation), rather than the collector of the VAS, and helps reduce distortion of the output stage also.
Can you explain with a diagram maybe intervening on my drawing?
the schematic it's a clone of jensen 918
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