Hi,
I was fiddling with Russ White's excellent diamante HP amplifier.
As PigletsDad pointed out in the original thread
http://www.diyaudio.com/forums/solid-state/114632-diamante-discrete-medium-power-opamp.html
, the circuit gives vanishing low distortion when configured as unity-gain buffer with bootstrapping the entire amplifier's rails so they go up and down with the output.
Simulation is attached, here's some of the results:
10K 20Vpp into 250ohms: 0.000001% THD
10K 10Vpp into 32ohms: 0.000073% THD
Might give a very nice HP buffer amplifier when combined with a low-distortion op-amp.
I also did some simulations on loop gain with parasitic inductances included. VAS comp cap will need to be around 1n and output network with 1uH inductor has to be added so it is stable into capacitive load up to 0.1uF. Theres some parts of the circuit that are quite sensitive to parasitic inductances (e.g. LTP emitters and output stage emitters) but overall it looks quite well-behaved.
Maybe THAT300 transistor arrays would do well for the input stage and current mirrors.
Suggestions?
I was fiddling with Russ White's excellent diamante HP amplifier.
As PigletsDad pointed out in the original thread
http://www.diyaudio.com/forums/solid-state/114632-diamante-discrete-medium-power-opamp.html
, the circuit gives vanishing low distortion when configured as unity-gain buffer with bootstrapping the entire amplifier's rails so they go up and down with the output.
Simulation is attached, here's some of the results:
10K 20Vpp into 250ohms: 0.000001% THD
10K 10Vpp into 32ohms: 0.000073% THD
Might give a very nice HP buffer amplifier when combined with a low-distortion op-amp.
I also did some simulations on loop gain with parasitic inductances included. VAS comp cap will need to be around 1n and output network with 1uH inductor has to be added so it is stable into capacitive load up to 0.1uF. Theres some parts of the circuit that are quite sensitive to parasitic inductances (e.g. LTP emitters and output stage emitters) but overall it looks quite well-behaved.
Maybe THAT300 transistor arrays would do well for the input stage and current mirrors.
Suggestions?
