MOS单管小甲

millwood

if you really want to build it, I would recommend that you buid Zen-Lite by Nelson Pass (http://www.passdiy.com/projects/zenlite1.htm).

I used those 12v halogen light bulbs as a load - they look very much like vaccum tubes. regular light bulbs work as well.

enjoy.

阿伟

有多少W？

狼嚎

电路对电源要求高吗

老爷车

谢谢M先生提供详尽资料  正在学习

summerabc

谢谢老爷车的指点!
我发现millwood也是这方面的行家

老爷车

先生您好，中午回家试过您提供的电路，出现问题不能解决。
用300W白炽灯作负载时，调整管子的偏置Vgs≈4V（为调整方便R1R2合并用68K精密可调电阻）至管子导通时，电源电压几乎全部降在灯泡上，电路不能正常工作。我用的管子是IRFP150。查过资料，IRFP150与IRFP240应属同类型管，具体参数见链接。
http://pdf.dzsc.com/88889/33163.pdf
http://pdf.dzsc.com/88889/13119.pdf

828282

老爷车

灯泡的阻抗并不是恒定的。

828282

millwood

原帖由 老爷车 于 2008-1-2 17:17 发表
先生您好，中午回家试过您提供的电路，出现问题不能解决。
用300W白炽灯作负载时，调整管子的偏置Vgs≈4V（为调整方便R1R2合并用68K精密可调电阻）至管子导通时，电源电压几乎全部降在灯泡上，电路不能正常工作 ...

that means that your mosfet is conducting too much (Vgs=4v may be a little bit too much for those).

so you may want to dial it down a little.

I would not target a given Vgs. instead, I would adjust the trimmer so that the voltage drop on the light bulb is slightly more than (V-5)/2.

BTW, I am assuming that you are using 220v light bulbs? for the same output power, their resistance is 4x that of 110v light bulbs which Nelson used in his article. That means you may have to parrallel a few of those light bulbs or live with smaller output power.

here is what I did a while back. it is very much like the Nelson SE MOSFET amp but without the feedback from the speaker. the power source is a 16v power supply for a notebook computer. the load, R1, is a 12v 10w halogen ligt bulb. R2/R5 is a 10k trimmer. voltage on the drain is about 9v, bot maximum output swing. the gain is about 4v and the amp can swing 8vpp into a 16ohm load for 0.5wrms.

You can reconfigure to get more out of it: using higher voltage, lower R1, use a constant current source to replace R1 (LM317 for example), or your a power transformer for R1, etc.

enjoy.

狼嚎

灯炮接在那个位置啊??????

millwood

原帖由 狼嚎 于 2008-1-2 20:13 发表
灯炮接在那个位置啊??????

r1.

millwood

the amp as constructed has fairly low (but adequate) input impedance (R3+R2//R5). or about 4.7k.

This can be a problem if C3 is small. If that's the case, you can use a 100k trimmer as R2/R5 to improve frequency response at <100hz.

狼嚎

是串接在R1与M1之间吗??

millwood

R1 IS the light bulb.

老爷车

谢谢先生。我刚刚用稳流管WL11P（960~1040mA/5.5~12V)作负载测试了一下，仔细调整偏置还是不行，不是左了就是右了，从波形上看不是上面削波就是下面削波，怎么也调不到一个最佳点.
电源电压：24V。

millwood

原帖由 老爷车 于 2008-1-2 20:50 发表
谢谢先生。我刚刚用稳流管WL11P（960~1040mA/5.5~12V)作负载测试了一下，仔细调整偏置还是不行，不是左了就是右了，从波形上看不是上面削波就是下面削波，怎么也调不到一个最佳点.
电源电压：24V。

do you have a source resistor? if you do, how big / small is it?

if your biasing is too sensitive to the trimmer, your source resistor may be too small.

老爷车

是的，R2用47K固定电阻，R1用18K精密多圈可调电阻，偏置电压变化非常平滑稳定。

millwood

原帖由 老爷车 于 2008-1-2 20:50 发表
谢谢先生。我刚刚用稳流管WL11P（960~1040mA/5.5~12V)作负载测试了一下，仔细调整偏置还是不行，不是左了就是右了，从波形上看不是上面削波就是下面削波，怎么也调不到一个最佳点.
电源电压：24V。

here is the same amp running at 24v rail.

the idle current is about 1amp, and Vgs is about 3.5v - which is pretty much the right number for D-MOSFET.

the Drain voltage is about 9.8v, vs. 9.9v for the same amp running at 16vdc.

the 2nd chart is for output waveform, at 1vp 20khz input.

the 3rd chart is for output waveform, at 2vp 20khz input - notice the symmetrical clipping?

enjoy.

millwood

原帖由 老爷车 于 2008-1-2 21:00 发表
是的，R2用47K固定电阻，R1用18K精密多圈可调电阻，偏置电压变化非常平滑稳定。

do you have a resistor on the source of the mosfet? between the source of the mosfet to ground? R6 in my shcematic? It is there to help stabilize bias and dc working point.