Can You Combat Johnson Noise and Shot Noise in Instrumentation?

In summary, the conversation discusses ways to combat Johnson noise and shot noise in the context of an instrumentation class. The speaker is seeking countermeasures to deal with these types of noise, but does not have them in their class notes or textbook. Suggestions include writing down the equations for their spectral density and considering factors such as temperature and other quantities in the formulas to lower the noise.
  • #1
ultimateguy
125
1
I was wondering if someone could give me some ways to combat Johnson noise and shot noise.

Thanks
 
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  • #2
Sure. What is the context? If it's noise in a sensor, what is the sensor technology? How much amplification do you need? What is the bandwidth and character of the signal that you are amplifying? What kind of back-end processing are you doing of the signal?
 
  • #3
There isn't really a context. I'm in an instrumentation class, and one of the questions is "Describe the origins of Johnson noise and Shot noise and appropriate countermeasures you can take to deal with them."

I know what they are, but I've been trying for the life of me to find out what the countermeasures are. I don't have them in my class notes and they're not in the textbook.
 
  • #4
Well, tell me a little about the effects of temperature and bandwidth on each.
 
  • #5
ultimateguy said:
There isn't really a context. I'm in an instrumentation class, and one of the questions is "Describe the origins of Johnson noise and Shot noise and appropriate countermeasures you can take to deal with them."

I know what they are, but I've been trying for the life of me to find out what the countermeasures are. I don't have them in my class notes and they're not in the textbook.

A simple way is to write down the equations giving their spectral density and/or their integrated RMS constribution, and to see what factors lower it. Hint: lowering the temperature might help for Johnson noise. But also other things play a role. Now look at the other quantities in the formulas...
 

1. What is Johnson noise?

Johnson noise, also known as thermal noise, is a type of noise that arises from the random thermal motion of electrons in a conductor. It is present in all electrical circuits and is a fundamental limit to the minimum amount of noise that can be achieved in a system.

2. How is Johnson noise different from shot noise?

Johnson noise is a type of noise that is present in all electrical circuits, while shot noise is a type of noise that occurs when a current is carried by individual particles, such as electrons. Shot noise is caused by the discrete nature of the particles and is present in systems where the current is low and the number of particles is small.

3. How is Johnson noise measured?

Johnson noise can be measured using a spectrum analyzer or an oscilloscope. By measuring the noise power over a range of frequencies, the Johnson noise can be determined. The noise level is directly proportional to the temperature of the conductor and the bandwidth of the measurement.

4. How does Johnson noise affect electronic devices?

Johnson noise can affect electronic devices in several ways. It can increase the noise level in a circuit, reducing the signal-to-noise ratio and potentially degrading the performance of the device. It can also lead to errors in measurements and limit the sensitivity of certain devices.

5. How can Johnson noise be reduced?

Johnson noise can be reduced by cooling the conductor, as the noise level is directly proportional to temperature. This is one of the reasons why electronic devices, such as transistors and amplifiers, are often designed to operate at lower temperatures. Additionally, using low-noise components and optimizing the design of the circuit can help reduce Johnson noise.

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