Cancelling out Power Supply Noise out COMPLETELY

In summary, the conversation discusses the possibility of designing a power supply with no noise, and the challenges of measuring noise in a circuit. It is suggested to use a battery for a low noise supply, but the value of R2 (600Mohms) and the bandwidth of interest must also be taken into consideration. The conversation also mentions the idea of using a HV cap to cancel out noise, but balancing the circuit and choosing the appropriate bandwidth can be difficult. Finally, it is noted that the high resistance of R2 can contribute to thermal noise unless the bandwidth is restricted.
  • #1
jonlg_uk
141
0
Hi I have a HV (R2) resistor that I want to test for noise. Assuming the 2 low voltage resistors are perfectly stable and HV R1 is also perfectly stable. How could I completely cancel out the noise of the power supply if the bridge was slightly unbalanced? Does any circuit exist that can do this?

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  • #2
No, there is no such thing as a PS with no noise. There are some very low noise supplies out there (use a battery) but I'd say that if the noise of the PS is that problematic you need to re-think your measurement methodology.
What is the resistance of R2? Remember that you also have the thermal noise (of R2 and the rest of the circuit) to deal with, and that can be substantial even compared to the input noise of a typical OP-amp.
Also, which bandwidth are you interested in?
 
  • #3
f95toli said:
No, there is no such thing as a PS with no noise. There are some very low noise supplies out there (use a battery) but I'd say that if the noise of the PS is that problematic you need to re-think your measurement methodology.
What is the resistance of R2? Remember that you also have the thermal noise (of R2 and the rest of the circuit) to deal with, and that can be substantial even compared to the input noise of a typical OP-amp.
Also, which bandwidth are you interested in?


Hi thanks for the reply. I know it is impossible to design and build a PS with no noise. The value of R2 is 600Mohms. I am looking for some type of circuit configuration that will cancel the noise and the HV of the power supply but at the same time allowing me to measure the noise of R2.

I have thought about using a HV cap in place of R1 as they have much less noise. However balancing the circuit so that it cancels out all the power supply noise is proving difficult and I am still reading some of the PS noise.
 
  • #4
But again. which BW are you interested in? If you are only interested in say the noise between 10kHz and 100kHz you might be OK with a PS that let's a lot of mains+harmonics through, but perhaps not OK with a switching supply that switches at e.g. 20 kHz and so on.
The BW is a crucial parameter when designing noise measurement experiments.

Also, a 600 Mohm resistor will give you a lot of thermal noise unless you restrict the BW of you circuit (a few mV/sqrt(Hz)).
 

Related to Cancelling out Power Supply Noise out COMPLETELY

1. What is power supply noise and why is it important to cancel it out completely?

Power supply noise refers to the fluctuations in voltage and current that can occur in an electronic system. This noise can cause interference and affect the performance of the system. It is important to cancel out power supply noise to ensure the stability and reliability of the system.

2. How does power supply noise affect electronic devices?

Power supply noise can cause a variety of issues in electronic devices, including signal distortion, reduced sensitivity, and decreased dynamic range. It can also lead to errors in data transmission and affect the overall performance of the device.

3. What are some common techniques for cancelling out power supply noise?

There are several techniques that can be used to cancel out power supply noise, including filtering, decoupling, and grounding. These techniques involve using components such as capacitors, inductors, and resistors to reduce or eliminate the noise signals.

4. How effective are these techniques in completely cancelling out power supply noise?

While these techniques can greatly reduce power supply noise, it is unlikely that it can be completely eliminated. There will always be some level of noise present in electronic systems, but by using these techniques, it can be reduced to a level that does not significantly impact the performance of the system.

5. Are there any trade-offs to consider when trying to cancel out power supply noise?

Yes, there can be trade-offs when trying to cancel out power supply noise. For example, adding filters and decoupling capacitors can increase the complexity and cost of a circuit. Additionally, these techniques can also affect the overall power efficiency of the system. It is important to carefully balance the need for noise cancellation with other design considerations.

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