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楼主 |
发表于 2005-7-15 13:56
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久违了……朋友们……
近半年做了几个甲类功放的试验版,声音有好有坏……但是它们的散热始终是让我头痛的事情……
所以又想起了JLH……MOS甲乙类输出版……
在外国的DIYAUDIO网站上看到了X-PRO(ALEX NIKITIN,前CREEK公司的首席设计师)的电路……我仿真后大为吃惊……
先到这里看看吧:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=3075&perpage=15&pagenumber=36
这是转贴过来的(方便大家阅览):
x-pro []
diyAudio Member
Offline
Registered: Apr 2003
Location: London
Post #540
quote:
Originally posted by tschrama
I really hope someonemore knowlegbeble can comment on the BJT/MOSFET exchange in a JLH 10W Class A 1969 amplifier... it makes my head spin..
Hi millwood and tschrama. I think I can feed you some information on this circuit and post here my own version of MOSFET development, somewhat based on JLH class A idea, which I've designed in 1992 and this amplifier still working quite happily in my daughter's room . Thought my amp was not built as class A, it could be easily converted into a proper class A amp by reducing the supply voltage and increasing the idle current - no other changes are needed for the circuit. I did publish this circuit in 1998 in the "Radiohobby" magazine as an illustration to a further development of it (a version of this later circuit could be found here: http://www.diyaudio.com/forums/show...&threadid=14320 ). The sound of this amp is very sweet... .
First, thought, a couple of buckets of cold water for millwood:
Your circuit loses a main attraction of JLH - it's symmetry. JLH is a proper push-pull circuit, working on the balance of the currents, as output bipolar transistors controlled by their respective base currents, and the driver redistributes the currents according to the signal. In your circuit, lower MOSFET is almost a current source, so the circuit is essentially an SE one. MOSFETs controlled by the gate-source VOLTAGE, so JLH way of control does not work. Also your circuit could be thermally not very stable and quite sensitive to the power supply variations and ripple.
Have a look at my circuit here and ask questions - I would be happy to answer.
Cheers
x-pro (Alex)
x-pro has attached this image:
Click the thumbnail to see the original image.
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