【教學】Cadence Spectre Transient Noise

 

今天要介紹的是如何在Cadence上使用ADE ，完成雜訊模擬。

What I want to introduce today is how to use ADE on Cadence to complete 

noise simulation.

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以下圖模擬當例子，在R=1K，C=1pF情況下，輸出VO的電壓變化。

The following figure simulates an example, in the case of R=1K, C=1pF, the voltage 

change of the output VO.

1.Open ADE XL/Maestro

先打開模擬環境，然後打開ADE XL或Maestro，選擇tran。

First open the simulation environment, then open ADE XL or Maestro, select tran.

2.Set Simulation Time

模擬時間跟我們Noise要看到多低頻有關西。

Noise Fmin=1/Ts。

因此可以知道，模擬時間太短是無法反映出電路本身的Flicker Noise。

Simulation time has nothing to do with how low frequencies we want Noise to see.

Noise Fmin=1/Ts.

Therefore, it can be known that the simulation time is too short to reflect the Flicker Noise 

of the circuit itself.

3.Set Simulation Accuracy

一般電路使用moderate是很夠用的，除非你電路是高解析的ADC/DAC。


Moderate is sufficient for general circuits, unless your circuit is a high-resolution 

ADC/DAC.

4.Set Noise Fmax

這邊讀者可以自己嘗試看看，這邊值設定越大會越接近實際情況。

當然這邊值大到一定程度，其實影響電路就很細微了，讀者可以自己嘗試看看自己電

路的邊界在哪邊。

Readers here can try it out for themselves. The larger the value here, the closer to the actual 

situation.

Of course, the value here is large to a certain extent, in fact, the impact on the circuit is very 

subtle. Readers can try to see where the boundary of their own circuit is.

5.Set Noise Fmin

這邊可以提供你另一個設定Fmin選擇，可是要注意的是，即便你這邊打1Hz，最後還

是Noise Fmin還是被1/Ts決定。

Here you can provide another option for setting Fmin, but it should be noted that even if 

you play 1Hz here, the Noise Fmin is still determined by 1/Ts.

6.Simulation Results

可以看到模擬結果，VO如預期的會變來變去。

公式Vo Noise rms=(KT/C)^0.5=64uVrms,模擬值為56Vrms

這邊跟手算有誤差原因，是我Noise Fmax設定不夠大，當Fmax夠大的時候會接近手

算的值！(可是相對模擬速度會慢很多)

As you can see the simulation results, VO changes as expected.

The formula Vo Noise rms=(KT/C)^0.5=64uVrms, the analog value is 56Vrms

The reason for the error here is that my Noise Fmax setting is not large enough. When 

Fmax is large enough, it will be close to the hand.

Calculated value! (But the relative simulation speed will be much slower)

以上，有興趣的朋友可以實做看看！

大家如果有疑問歡迎提出，或者有其他方式也歡迎拿出來討論。

The above, interested friends can actually do it!

If you have any questions, you are welcome to raise them, or you are welcome to discuss 

them in other ways.