x*p 发帖数: 77 | 1 我作个系统其中需要做个Lock-in Amplifier子系统来跟踪
而Lock-in amp的需要一个稳定的Sine Ref
这个Sine ref信号的稳定度很大程度决定了测试的精度
目前需要输出大概1V,1mV的稳定度的Sine wave
我的环境基本能保持温度恒定,所以半导体器件的温飘问题可能不是很大
我搭Wien-Bridge用IN4148乾位,效果不太理想,5mV稳定度的样子
不知道各位大大有没有比较好的推荐的
拜谢 |
s**g 发帖数: 66 | 2 how about DDS plus filter? |
x*p 发帖数: 77 | |
s**g 发帖数: 66 | 4 Wien-Bridge has decent distortion performance. But the amplitude control may
not be as good as you like to see.
DDS uses high speed DAC with built-in look-up table to generate waveform (
sine/triangular/square). The frequency accuracy is realized by internal
oscillator or PLL referenced to an external crystal; amplitude accuracy is
obtained by the DAC.
Add LPF or BPF to suppress distortion and noise (to meet 1mVrms spec). Add
buffer if you like to scale up swing or to drive considerable load or |
g****t 发帖数: 31659 | 5 请问为啥Wien-Bridge类型的振幅控制会不好?
我觉得精度不够就是二极管工作区的曲线太陡或者太不陡,
把Wien-Bridge里的二极管接个可调电阻,
然后调一下说不定精度就上去了吧?
Wien-Bridge has decent distortion performance. But the amplitude control may
not be as good as you like to see.
DDS uses high speed DAC with built-in look-up table to generate waveform (
sine/triangular/square). The frequency accuracy is realized by internal
oscillator or PLL referenced to an external crystal; amplitude accuracy is
obtained by the DAC.
Add LPF or BPF to suppress distortion and noise
【在 s**g 的大作中提到】 : Wien-Bridge has decent distortion performance. But the amplitude control may : not be as good as you like to see. : DDS uses high speed DAC with built-in look-up table to generate waveform ( : sine/triangular/square). The frequency accuracy is realized by internal : oscillator or PLL referenced to an external crystal; amplitude accuracy is : obtained by the DAC. : Add LPF or BPF to suppress distortion and noise (to meet 1mVrms spec). Add : buffer if you like to scale up swing or to drive considerable load or
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s**g 发帖数: 66 | 6 Wien Bridge osc uses positive feedback to achieve frequency selection and
negative feedback to obtain start-up condition (overall loop gain >1).
There is a third feedback -- a thermal/PD/diode or FET clamping scheme - to
get amplitude control (negative feedback drops when oscillation amplitude
increases). But in the amplitude control loop, open loop gain (from
amplitude increase to variation of negative feedback gain) typically is not
very big. Therefore the suppression of amplitude fluctuation
【在 g****t 的大作中提到】 : 请问为啥Wien-Bridge类型的振幅控制会不好? : 我觉得精度不够就是二极管工作区的曲线太陡或者太不陡, : 把Wien-Bridge里的二极管接个可调电阻, : 然后调一下说不定精度就上去了吧? : : Wien-Bridge has decent distortion performance. But the amplitude control may : not be as good as you like to see. : DDS uses high speed DAC with built-in look-up table to generate waveform ( : sine/triangular/square). The frequency accuracy is realized by internal : oscillator or PLL referenced to an external crystal; amplitude accuracy is
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x*p 发帖数: 77 | |