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Old 1st February 2013, 09:19 PM   #171
smms73 is online now smms73  Portugal
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Mirror_bjt.asc I have post the models in here already.
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Old 1st February 2013, 09:47 PM   #172
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I have change the value of R2 for 500 and 250 ohns to change the gain to 8 and 16.
the results are with 8 X

0.000027% 4 Vp-p out
0.000072% 8 V pp
0.00025% 16 Vpp

with 16X

0.000039%
0.000111%
0.000392%

Even with a gain of 32x the distortion is only 0.000086 at 4 volts p-p out.

It seems that voltage gain is not a problem.
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Last edited by smms73; 1st February 2013 at 09:51 PM.
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Old 1st February 2013, 10:52 PM   #173
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Connect the collectors of Q16 and Q18 to ground. They only add distortion.
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Old 2nd February 2013, 06:13 AM   #174
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Originally Posted by smms73 View Post
Mirror_bjt.asc I have post the models in here already.
Thanks Sergio.
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Old 2nd February 2013, 07:05 AM   #175
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Sergio, I think that your circuit is really excellent demonstration of an engineering skill. I don’t know you but I am glad that you participate in this thread. I know about Keantoken a bit more and followed his fascinating progress in this forum. I am just an old retired telecommunication engineer and audio is my hobby to kip my old gray matter oiled. What I learned more then forty years ago about semiconductors now slowly is coming back and I started to use spice simulator not so long ago.
What do you think if your circuit could be made simpler whiteout loosing to much of its performance, still distortion could stay in ppm region?
Another thing to make it with high gain, let say 20 to 30 dB and then add powerful output buffer to get power amp with no GNFB. I was trying to simulate an output buffer(trying different configuratio) but never was satisfied with distortion level.
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Old 2nd February 2013, 11:35 AM   #176
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Here is new shuntreg simulation. I am trying to keep just one jfet ccs as in this case output voltage adjustment is possible with one trimer(R7 in this case). Here CCS voltige is 2.2 V and I think its on safe side of the knee(in saturation region).
dado
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Old 2nd February 2013, 12:23 PM   #177
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Quote:
Originally Posted by keantoken View Post
But A and B perform the same when you have 220/75 degeneration. Do you know of a better way to increase gain?
A 220/75 degeneration ratio will imbalance the mirror, and it will lose some distortion cancellation property.

one way to do the job without loosing balance is like this , the penality is adding 2 bjt and 2 resistors.
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Old 2nd February 2013, 12:45 PM   #178
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Thanks Damir for your kind words, I'll try to do what you ask , but the components used here are really cheap , the 20 transistors used in this circuit will cost less than a dollar. I do not really see the problem

About the power supply , have you consider The Kmultiplier from Kean, I use a very similar soluction ,It is really very low noise, and have very good stability , and is less complex than the one you are doing. But the output impedance is a bit higher.
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Old 2nd February 2013, 02:29 PM   #179
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Originally Posted by smms73 View Post
Thanks Damir for your kind words, I'll try to do what you ask , but the components used here are really cheap , the 20 transistors used in this circuit will cost less than a dollar. I do not really see the problem

About the power supply , have you consider The Kmultiplier from Kean, I use a very similar soluction ,It is really very low noise, and have very good stability , and is less complex than the one you are doing. But the output impedance is a bit higher.
Someone said the less is better, and Einstein said " Everything should be made as simple as possible, but not simpler". OK it is question of PCB too, simpler to make.
Regarding power supply, there is oppinion that nothing can beat good shunt regulator and I need to lower power voltage to as mine transformer has 2x30V.
Damir
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Old 2nd February 2013, 03:32 PM   #180
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Here is a similar circuit but with current sources instead of current mirrors.
I cut some of the fats, to get it in accordance with Einstein

The distortion is 0.000069% at 4 V p-p with a gain of 16x

One of the advantages of using current sources like that is that the psrr is higher, I have made circuits with this topology with psrr of 80db.
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