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原帖由 power77 于 2008-10-17 21:38 发表 
48楼的电路是原版的,我做过的第一块功放板,也是弗山八达公司的前身----八达新科技服务部的第一个产品,这个板做出来的零漂非常大,可以到2~3伏,而且调好中点了还不稳定随着市电电压飘来飘去的,想玩这个的喇 ...
because the dumbass didn't design the amp properly. see the attached.
1) there needs to be a DC blocking capacitor (220u - 470u) on the feedback loop.
2) Q1 needs to have a small capacitor between its b and c pins to maintain stability.
3) the offset adjustment mechanism is poorly designed. replace that 27v zener with a 15k resistor, and replace D4 with a forward-biased LED (1.9 - 2.7v), or two forward-biased 1n4148.
I would replace 2n5401 with a larger transistor but for small output power the 2n5401 should work. |
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