Signal to noise ratio for thermal and shot noise

In summary, the task is to calculate the signal to noise ratio of a sensor output connected to a parallel RC circuit with resistance of 50 ohms and capacitance of 10pF at a temperature of 300K. The formula for SNR is given as either 10 log (power of signal/ power of noise) or 20 log (voltage signal / voltage noise). The voltage on a capacitor can be calculated using V = Q/C, and the thermal noise can be calculated using 4kTf, where k is the Boltzmann constant and f is the frequency bandwidth. The noise bandwidth for this circuit is determined by the RC filter. It is unclear if the 10,000 electrons mentioned in the task
  • #1
Outrageous
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Homework Statement


The output of a sensor which produces 10000 electrons is connected to parallel RC circuit with Resistance= 50 ohm, and the capacitance=10pF.
Calculate the signal to noise ratio at temperature 300K.


Homework Equations


SNR= 10 log (power of signal/ power of noise)
Or SNR = 20log ( voltage signal / voltage noise)



The Attempt at a Solution


Voltage=C/Q=624.15V
Power of signal= voltage square / resistance= 7791.2 J
But how to calculate power of noise? The thermal noise = 4kTf, where k is boltzman constant, f is frequency bandwidth. Yet not given , but I can only think of these formula for thermal noise and 10000 electron need to include shot noise?

Please help
 
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  • #2
Check your equation for the voltage on a capacitor--it's not quite right. Then use this hint: the noise bandwidth is determined by the RC filter.
 
  • #3
Is that 10,000 electrons or 10,000 electrons per second?
 
  • #4
marcusl said:
Check your equation for the voltage on a capacitor--it's not quite right. Then use this hint: the noise bandwidth is determined by the RC filter.

Yup, V =Q/C , and f=1/(2∏RC)
But why is this the Bandwidth? The impedance of capacitor is same as resistance so we get maximum power for?
And 10000 electrons need to consider shot noise? If I consider, so I just add thermal noise voltage and shot noise together to get the total voltage noise?
 
  • #5
rude man said:
Is that 10,000 electrons or 10,000 electrons per second?
10000 electrons without telling time, but even telling time, I still can calculate the thermal and shot noise.
 

FAQ: Signal to noise ratio for thermal and shot noise

1. What is the signal to noise ratio (SNR) and why is it important?

The signal to noise ratio (SNR) is a measure of the strength of a signal compared to the background noise. It is important because it indicates how well a signal can be detected and distinguished from the noise.

2. What is thermal noise and how does it affect the SNR?

Thermal noise is a type of noise caused by the random motion of electrons in a circuit or system. It is also known as Johnson noise or Nyquist noise. Thermal noise increases with temperature and can decrease the SNR by adding unwanted noise to the signal.

3. What is shot noise and how does it impact the SNR?

Shot noise is a type of noise caused by the random arrival of electrons at a detector or sensor. It is also known as Poisson noise. Shot noise can decrease the SNR by adding noise to the signal, but it can also provide useful information about the signal itself.

4. How is the SNR calculated for thermal and shot noise?

The SNR for thermal noise is calculated as SNR = (mean signal power)/(mean thermal noise power). For shot noise, the SNR is calculated as SNR = (mean signal power)/(mean shot noise power).

5. How can the SNR be improved for thermal and shot noise?

The SNR can be improved for thermal noise by reducing the temperature of the system. For shot noise, the SNR can be improved by increasing the number of electrons or photons detected, or by using averaging techniques to reduce the random nature of the noise.

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