测试用途的 20KHZ 振荡电路 - 移相

e3po · 发表于 2012-10-29 06:32:03

millwood · 发表于 2012-10-30 07:29:26

In May 1987, the Radio Magazine has a signal generator. The AF portion of it is actually very good. Check it and simulate it before you actually build one. The original design uses bjt but a jfet greatly simplifies the design.

e3po · 发表于 2012-10-30 06:51:05

epawp 发表于 2012-10-28 17:27
楼主仅仅是仿真吧。如果是真的要做个实用的，建议您采用小功率的功放IC或者是运放，原因有：
1）三节RC等值 ...

多谢！

做来玩的，三极管太多了。

66718 · 发表于 2012-10-30 17:35:19

我在电子报上见过一个类似电路，我曾经实验做50hz振荡，结果是以失败而告终。

e3po · 发表于 2012-10-31 09:26:48

本帖最后由 e3po 于 2012-10-30 18:20 编辑

epawp 发表于 2012-10-28 17:27
楼主仅仅是仿真吧。如果是真的要做个实用的，建议您采用小功率的功放IC或者是运放，原因有：
1）三节RC等值 ...

很奇怪的现象，滞后型的反而谐波很多（-20dB 以上）。

电路按照顶楼的搭建，谐波不多（-20dB 以下）。

epawp · 发表于 2012-10-29 09:27:53

楼主仅仅是仿真吧。如果是真的要做个实用的，建议您采用小功率的功放IC或者是运放，原因有：
1）三节RC等值移相电路有两种，超前和滞后，超前的高次谐波比滞后的要大些；
2）使用三极管对移相网络会有负载效应，将影响振荡频率，要想微调频率比较困难，所以用运放或功放IC（也属于运放范围），其输入阻抗比较大，输出阻抗比较小，影响会很小；
3）运放的增益比三极管要大，而且可调整，比起您的电路用射随器做输出要好，该电路的输出幅度将会很小；
4）其实用文氏桥很好的，其选频特性比移相的要好，衰减系数也只有三分之一，加个稳幅就可以。

e3po · 发表于 2012-10-31 12:31:37

millwood 发表于 2012-10-29 15:29
In May 1987, the Radio Magazine has a signal generator. The AF portion of it is actually very good. ...

"Ham Radio" or just "Radio"

Can't find it from the web.

millwood · 发表于 2012-11-8 22:09:28

Sorry, here is the one, from the chinese Radio magazine ("Wireless"?).

sig gen radio magazine 73-02.PNG

Hope it helps.

millwood · 发表于 2012-11-8 22:11:34

In case you need, here is the schmatic for heathkit ig5280.

sig gen heathkit ig5280.PNG

The AF portion actually is hard to get to work.

e3po · 发表于 2012-11-9 12:13:42

millwood 发表于 2012-11-8 06:09
Sorry, here is the one, from the chinese Radio magazine ("Wireless"?).

Thanks a lot!

e3po · 发表于 2012-11-9 12:16:07

本帖最后由 e3po 于 2012-11-10 12:38 编辑

millwood 发表于 2012-11-8 06:11
In case you need, here is the schmatic for heathkit ig5280.

Thanks!! I'll try that later.

now I have this problem, couldn't get a Wien Bridge Oscillator to produce sine wave:

I think I must miss some very important thing but I 'm too dumb to tell.

e3po · 发表于 2012-11-10 12:13:05

本帖最后由 e3po 于 2012-11-10 12:35 编辑

on LTspice it doesn't oscillate, scratching my head.

update: it'does. have to wait untill 66th mS.

Patience, Patience, Patience

millwood · 发表于 2012-11-10 07:13:14

Those guys need 3+ gain to work. so I would cut out R11 and increase R4 to 2.2k (<4.7k/2).

Hope it helps.

millwood · 发表于 2012-11-10 07:19:10

That did work.

Also, try to use 5484 instead.

millwood · 发表于 2012-11-10 20:34:27

next time, try a simple rail version.

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