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Old 28th December 2012, 01:04 PM   #81
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Kean, what do you think about BC182/212 for current mirrors? I have them from long time ago.
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Old 28th December 2012, 02:24 PM   #82
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Originally Posted by keantoken View Post
It is supposed to improve PSRR. Edmund uses a similar technique in his Super TIS. It conserves the rail-modulated currents through the 150k resistors, and combines them so they cancel. I seem to recall that in the original configuration, asymmetric rail variations would cause higher PSRR than normal. Forcing the 150k resistor current to flow through both loops caused asymmetric PSRR to improve. But I also seem to recall there were some innocent gaffes made on that part of the circuit that got corrected later.
Edmond abandoned the scheme later on and I see the reason why.
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Old 28th December 2012, 03:37 PM   #83
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Edmond abandoned the scheme later on and I see the reason why.
Will you say why?
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Old 28th December 2012, 03:51 PM   #84
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THD offcourse, just as I predicted, see page 4 of his thread, he found another way of increasing PSRR though, see his latest schematic on his website. His search though was for better PSRR and found better THD instead by rather using classical super pair arrangement. I must see how well this other scheme works.
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Old 28th December 2012, 04:56 PM   #85
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Originally Posted by homemodder View Post
THD offcourse, just as I predicted, see page 4 of his thread, he found another way of increasing PSRR though, see his latest schematic on his website. His search though was for better PSRR and found better THD instead by rather using classical super pair arrangement. I must see how well this other scheme works.
I simulated with different values of the resistor connected between Q9 and Q10 emitters and there is no significant change in THD or PSRR, so I stick with circuit as it was with Baxandall super pairs. I have Dimitry Danyuk enhaced cascode, but I think it could not be implemented here.
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Old 28th December 2012, 08:31 PM   #86
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The BC182/212 look like clones of the BC5xx series. They have Vce of 50V which is 5V better than the BC560/550. It looks like they were obsoleted by the BC556C/546C? But aside from the low Vce they appear to be as good as any BC5xx.
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Old 28th December 2012, 08:54 PM   #87
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The BC182/212 look like clones of the BC5xx series. They have Vce of 50V which is 5V better than the BC560/550. It looks like they were obsoleted by the BC556C/546C? But aside from the low Vce they appear to be as good as any BC5xx.
John Linsley Hood used them regularly.
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Old 29th December 2012, 09:34 AM   #88
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I simulated with different values of the resistor connected between Q9 and Q10 emitters and there is no significant change in THD or PSRR, so I stick with circuit as it was with Baxandall super pairs. I have Dimitry Danyuk enhaced cascode, but I think it could not be implemented here.
dado
In your case might be insignificant althouh Im betting on that with resistor between the two emitters there is a definite drop in THD however small. In my case with a power amp where a high power outputstage must be driven the THD is nearly 25 % worse off for the crosscoupling. Even Edmond had a useful reduction in THD. The action that makes a super pair so linear is somewhat negated by the action of the cross coupling. Classical Baxandall super pairs dont use cross coupling. When I have some time Ill look at the scheme later adopted by Edmond.
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Old 29th December 2012, 11:18 AM   #89
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In your case might be insignificant althouh Im betting on that with resistor between the two emitters there is a definite drop in THD however small. In my case with a power amp where a high power outputstage must be driven the THD is nearly 25 % worse off for the crosscoupling. Even Edmond had a useful reduction in THD. The action that makes a super pair so linear is somewhat negated by the action of the cross coupling. Classical Baxandall super pairs dont use cross coupling. When I have some time Ill look at the scheme later adopted by Edmond.
I simulated only current conveyor part, without output buffer, with cross connected resistors and resistor connected between emitters. I could get very insignificant drop of THD20k from 2.05 ppm to 2.02ppm but in that case the resistor was 4.7 kohm and dissipated 0.9 W(with 13 mA). One side effect was that power dissipation on Q6 and Q8 droped to 100 mW and low power transistor could be used. I am not sure if this is better.
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Old 31st December 2012, 03:35 PM   #90
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Happy New Year to everybody.
Damir
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