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Analog Line Level Preamplifiers , Passive Pre-amps, Crossovers, etc.

Jfet folded cascode with diamond buffer opamp
Jfet folded cascode with diamond buffer opamp
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Old 27th April 2013, 10:18 PM   #31
sonnya is offline sonnya  Denmark
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I Will test with ssm2212 tomorrow .

The input bias current Will be less than 5uA.

- Sonny
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Old 27th April 2013, 10:45 PM   #32
sonnya is offline sonnya  Denmark
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Just a shot of the difference on input and output on the squarewave signal.

Lightblue is the input.
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File Type: png inputoutputcompare.png (18.4 KB, 184 views)
Attached Files
File Type: pdf inputoutputcompare.pdf (32.5 KB, 12 views)
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Old 27th April 2013, 11:51 PM   #33
sonnya is offline sonnya  Denmark
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I have tested the JFET opamp with NPN pair instead of jfet's.

Some of the data is:
  • Less than 2mV input offset
  • less than 4uA input offset current
  • Distortion 10 times lower at 10KHz into 220R load

The picture below is as with all the other measurement
  • 47pF compensation
  • 680mVrms out
  • 10KHz Sine
  • 0dB gain

Distortion is 0.0018% - Generator is: 0.0013%
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File Type: jpg fft 10KHz 220R NPN pair.jpg (115.2 KB, 180 views)

Last edited by sonnya; 28th April 2013 at 12:06 AM. Reason: added measurement
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Old 28th April 2013, 10:45 AM   #34
AndrewT is offline AndrewT  Scotland
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still the post1 schematic?
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regards Andrew T.
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Old 28th April 2013, 01:02 PM   #35
sonnya is offline sonnya  Denmark
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Quote:
Originally Posted by AndrewT View Post
still the post1 schematic?
No, it is changed a bit.

See attachment.

instead of folded cascode, i use current mirrors now. But performance is exactly the same.
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File Type: jpg fft 10KHz 1K load 11xgain NPN pair.jpg (118.4 KB, 147 views)
File Type: jpg fft 1KHz 1K load 11xgain NPN pair.jpg (112.3 KB, 137 views)
File Type: jpg fft 1KHz No load 11xgain NPN pair.jpg (117.3 KB, 135 views)

Last edited by sonnya; 28th April 2013 at 01:32 PM.
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Old 28th April 2013, 01:34 PM   #36
sonnya is offline sonnya  Denmark
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Here is the schematic of Bipolar version of the Jfet opamp
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File Type: pdf ssm2212rzopampv10.pdf (49.4 KB, 127 views)
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