20204-9.22

希望在周二之前把作业做完。 Measurement 还是有好多没学会啊。analog感觉代尔夫特的课件讲得太浅显了，漏了很多信息让人云里雾里。还是江老师做的课件好。

I. measurement 

 完全不会的知识点：1/f corner frequency。

复习一下：

Resolution & Accuracy

• resolution refers to the smallest change that can be detected. 
• limited by stochastic errors
• can be improved by filtering, why?

Three kinds of noises: thermal noise, shot noise, and flicker noise.

thermal noise

• also known as Johnson Noise
• limits system resolution
• random, but obeys Gaussian distribution
• Has a uniform/flat spectrum, that's why it's called "white noise"
• noise power Pn=4 kT, unit is [W/Hz] k is Boltzmann's constant;
  • therefore, the noise voltage spectrum density is vn = sqrt (4kTR)   [V/sqrt(Hz)]
  • therefore, the noise current spectrum density is vn = sqrt (4kT/R)   [A/sqrt(Hz)]
• V_n,rms = sqrt ( 4kTR(f1-f2) )

Shot noise

• also white noise
• occur in semiconductor, not in metallic 
• In^2 = sqrt ( 2*q*l),  q is charge in a electron, I is average current
•  

Flicker noise

• PSD proportional to 1/f 
• corner frequency: when white noise = 1/f noise
• attenuation speed with frequency :  -3dB / octave
• 
• can be simulated with a voltage source in series with gate of MOSFET
• 

问题

1. why can resolution be improved by filtering? -ch1. 1. error sources

怎样可以改进记笔记的方式呢？我的需求包括： 1. 能打字；2. 能放公式和图片；3. 能传到网络上，在云端便捷查看