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Hi folks.
I think that I am on the right track finally.I ve tested the amp and it works with the following configurations.
1)1 transistor ccs per stage using a blue led.First stage has 2n5401 and second stage has bd140(I am planning to use 2n5401 here too)
2)vas stage is darlington.The driver is 2n5551 and the output (of the vas stage )mje340.I use 2n5551 for the protection of vas stage.
3)Output stage will have mje340-350 for drivers and 2sc3281 and 2sa1302 for output(only one pair is used).
No vi limiter is used.
1st stage ccs at 6mA
2nd stage ccs at 15 mA
Vas current limit 40mA
Input resistance and feedback is 2.2k for low noise. Ground resistor is 330ohm in series with 100uf.Input coupling is 22uf.
Have added 100ohm emitter degeneration at diff amp and 47 ohm at current mirror emitters.
I noticed that the biasing problem (the one that when I try to bias the ops conducts uncontrollably and burns) occurs only when I place the turn off resistors in darlington or the biasing resistors in Cfp.
However bd911 and bd912 do that with or without them.
I have seen an improvement in oscillations with the use of zobel network and with the use of 47uf of across the vbe multiplier.I have seen no difference with the output inductor
Thank you
I think that I am on the right track finally.I ve tested the amp and it works with the following configurations.
1)1 transistor ccs per stage using a blue led.First stage has 2n5401 and second stage has bd140(I am planning to use 2n5401 here too)
2)vas stage is darlington.The driver is 2n5551 and the output (of the vas stage )mje340.I use 2n5551 for the protection of vas stage.
3)Output stage will have mje340-350 for drivers and 2sc3281 and 2sa1302 for output(only one pair is used).
No vi limiter is used.
1st stage ccs at 6mA
2nd stage ccs at 15 mA
Vas current limit 40mA
Input resistance and feedback is 2.2k for low noise. Ground resistor is 330ohm in series with 100uf.Input coupling is 22uf.
Have added 100ohm emitter degeneration at diff amp and 47 ohm at current mirror emitters.
I noticed that the biasing problem (the one that when I try to bias the ops conducts uncontrollably and burns) occurs only when I place the turn off resistors in darlington or the biasing resistors in Cfp.
However bd911 and bd912 do that with or without them.
I have seen an improvement in oscillations with the use of zobel network and with the use of 47uf of across the vbe multiplier.I have seen no difference with the output inductor
Thank you
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