I believe I see three suggestions here:
1) degenerate both LTPs
2) improve the current mirror in the second
3) Q5, but I have no idea what it's doing
It's also upside down, but I assume that's just to use easier-to-find N-channel JFETs? (I happen to have some 2SJ109s burning a hole in the bottom of a drawer, so I like the other orientation.)
I'm going to play with (1) first because stability is still marginal with a decent slew rate and perhaps I can increase the current for better slew rate without increasing the gain.
1) degenerate both LTPs
2) improve the current mirror in the second
3) Q5, but I have no idea what it's doing
It's also upside down, but I assume that's just to use easier-to-find N-channel JFETs? (I happen to have some 2SJ109s burning a hole in the bottom of a drawer, so I like the other orientation.)
I'm going to play with (1) first because stability is still marginal with a decent slew rate and perhaps I can increase the current for better slew rate without increasing the gain.
I didn't have to use that little after all. With 47R in the first diff I'm getting 50uV/sec and DC - 100kHz frequency response with reasonable margins (45º and 7dB). Whoo hooo!
It's difficult to balance the comp strategies because I need Miller compensation for the gain margin, phase lead compensation for the phase margin, and input filtering to move both back a bit.
I tried transitional Miller, and Miller around the output stage, but had no joy.
It's difficult to balance the comp strategies because I need Miller compensation for the gain margin, phase lead compensation for the phase margin, and input filtering to move both back a bit.
I tried transitional Miller, and Miller around the output stage, but had no joy.
Jeff,
Michael has a point (but if you make the front end rails high enough and reduced the current in the second differential since you have drivers)........I woulds still address early effect in the mirror and improve its accuracy.
Jam
Michael has a point (but if you make the front end rails high enough and reduced the current in the second differential since you have drivers)........I woulds still address early effect in the mirror and improve its accuracy.
Jam
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I'll have to have a look at that again. Boosting the second diff current was the only way I could get the slew rate up. But I have no Miller comp on the drivers, so I'm not sure what the extra current is required for....
Cheers,
Jeff.
But cross-over distortion? Pfffft. What cross-over? This baby's biased at 3A!
I think he is referring to R32, R33
Doug Self has also noted this in the design of his Blameless Amplifier. 
Switching speed seems to be the issue here. Granted the example is for bi-ploars it remains to be seen what it does in the Buzz Bomb,
Jam
Switching speed seems to be the issue here. Granted the example is for bi-ploars it remains to be seen what it does in the Buzz Bomb,
Jam
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