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Old 30th April 2010, 11:58 AM   #1
sekhar is offline sekhar  India
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Lightbulb my little QUASI AMP

Here is the schematiccs for Little QUASi AMp in simulator it run fine with THD ratings as low as 0.01% lets see wat do experienced people have to say




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sekhar
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Old 30th April 2010, 12:13 PM   #2
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Give it some emitter degeneration on the LTP & check the distortion then, should make the whole thing more linear.

100 ohm should be fine on each emitter
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Old 30th April 2010, 01:15 PM   #3
sekhar is offline sekhar  India
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here is updated schematic as suggested by EVENT HORIZON .............. sorry to say but after addding the resistor in emitter of the LPT the THD rating actually increased from 0.01 to 0.03


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Old 30th April 2010, 01:15 PM   #4
sekhar is offline sekhar  India
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the schematics

Click the image to open in full size.


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sekhar
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Old 30th April 2010, 01:24 PM   #5
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lol, can't win them all i guess
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Old 30th April 2010, 01:37 PM   #6
AndrewT is online now AndrewT  Scotland
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Try increasing the LTP tail current to restore the LTP gain to what it was.

Then try adding a low value emitter resistor to the VAS.
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Old 1st May 2010, 08:24 AM   #7
sekhar is offline sekhar  India
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seems that I should go and make pcbs straight forward the design seems to good enough wat say every body any more modification needed ?????????????????



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sekhar
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Old 1st May 2010, 11:01 AM   #8
godfrey is offline godfrey  South Africa
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I don't think you need the diode between the emitter of the BD140 and the output. That is good for bipolar quasis, but not with mosfets.

Otherwise it looks OK, so long as the output bias is set correctly.
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