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Low Phase Noise Amplifier Design

DhVJ

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Hi,
I was looking for some literature that would help me in getting a better understanding for the design of low phase noise amplifier. I have not found any and I am not able to differential between low noise and low phase noise design. Could someone please help me in getting an idea of how to design and what all should be considered while designing a low phase noise amplifier?
It would be really helpful if I get a publication or any reference for my understanding.

Thank you.
 

KlausST

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Hi,

"Noise" with Opamps is the voltage noise and current noise in an analog system.
"Phase noise" mainly is the timing noise of the edges of a digital system. But may be used in HF clock generators, too.


Since the Opamp is a purely analog device ... its quite unusual to talk about phase noise.
I'm not sure if it makes sense to calculate phase noise if an Opamp. Maybe it does. What is your application / requirement.

Some say "Opamp" but mean "comparator", which shares the same schematic symbol, but has digital output. Is this the case?

Klaus
 

DhVJ

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I meant the design of an amplifier with low phase noise with an analog output. I have seen many production of this LPNA but have not found any paper or publication over the design.

And I would like to know about the design for the frequency instabilities(phase noise) and not timing jitters.

Thank you.
 

KlausST

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Hi,

I see, you talk about HF.
Sadly I'm not that familiar with HF. There will be others that better can assust you.

My thoughts:
Phase noise and timing jitter will relate to each other.
I think phase noise is more related to signal generation (oscillators) than signal processing (filters, amplifiers), thus I recommend to give more informations about your application (the use of the Opamp).

Klaus
 

DhVJ

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Hi,
I will be designing a LPNA for different technology platforms like CMOS, SiGe and then compare the noise performances.

I would want to know about the design since i did not find any source to get better understanding and a starting point.

Thank you.
 

sutapanaki

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Low phase noise amplifiers do work with clocks and these are kind of buffers for oscillators, that's why they are required to not contribute much to the phase noise or jitter of the oscillations. Here is from ADI's web site

" Low Phase Noise amplifiers are critical for many applications requiring high signal integrity. This is especially relevant in instrumentation, defense, and telecommunication applications where low phase noise amplifiers are becoming increasingly important as the oscillators improve. Phase noise is described as the close-in noise to the carrier that can often appear as jitter on a clock signal. "
 

DhVJ

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Low phase noise amplifiers do work with clocks and these are kind of buffers for oscillators, that's why they are required to not contribute much to the phase noise or jitter of the oscillations. Here is from ADI's web site

" Low Phase Noise amplifiers are critical for many applications requiring high signal integrity. This is especially relevant in instrumentation, defense, and telecommunication applications where low phase noise amplifiers are becoming increasingly important as the oscillators improve. Phase noise is described as the close-in noise to the carrier that can often appear as jitter on a clock signal. "
Hi,
Yes I understand the importance and about phase noise but I want to know about the design of low phase noise amplifier. I would like to know the design steps which should be followed especially in this case, since it is difficult for me to differentiate between LNA and LPNA.

It would be helpful if I get a reference to understand the design.
Thank you.
 

sutapanaki

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I don't think someone can give you a recipe for design. I would say start by designing an amplifier/buffer that will at least work at the frequency you want. Then run pnoise, look at the spectrum, it will upconvert flicker noise at the tone you have at the input. Try to reduce the skirts by identifying what contributes to that.
 

Puppet123

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Technically, this post is in the wrong section, since it is a distributed amplifier, which is a MMIC, and microwave, so it should be in the microwave section.

Anyhow, a low phase noise distributed amplifier needs to have low noise and low frequencies and therefore one of the those noise sources is the 1/f noise. It's all about the terminations and they are typically active terminations when designing distributed amplifiers. Typically, HBTs have lower 1/f noise than FETs, so using bipolar would be better.

In an LNA for wireless applications, we are designing a narrow band design, so typically we don't care about 1/f noise. But for low phase noise, we care about 1/f noise if we are designing for low phase noise and if doing a wideband amplifier.

So to design, you design a distributed amplifier as usual and then be mindful about the terminations as the papers below explain.

See: www.mwrf.com/technologies/components/article/21848553/consider-lpnas-for-your-next-design

A few papers have been published about this and they are below:

A. Kopa, A.B. Apsel, “Distributed Amplifier With Blue Noise active Termination,” IEEE Microwave and Wireless Components Letters, vol. 18, no. 3, March 2008.

P. K. Ikalainen, “Low-Noise distributed amplifier with active load,” IEEE Microw. Guided Wave Lett., vol. 6, no. 1, pp. 7–9, Jan. 1996.

Next time, put the post in the right section. Also, knowing the application, your specifications and what you tried so far would be helpful - also what process you are using,
 
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DhVJ

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Technically, this post is in the wrong section, since it is a distributed amplifier, which is a MMIC, and microwave, so it should be in the microwave section.

Anyhow, a low phase noise distributed amplifier needs to have low noise and low frequencies and therefore one of the those noise sources is the 1/f noise. It's all about the terminations and they are typically active terminations when designing distributed amplifiers. Typically, HBTs have lower 1/f noise than FETs, so using bipolar would be better.

In an LNA for wireless applications, we are designing a narrow band design, so typically we don't care about 1/f noise. But for low phase noise, we care about 1/f noise if we are designing for low phase noise and if doing a wideband amplifier.

So to design, you design a distributed amplifier as usual and then be mindful about the terminations as the papers below explain.

See: www.mwrf.com/technologies/components/article/21848553/consider-lpnas-for-your-next-design

A few papers have been published about this and they are below:

A. Kopa, A.B. Apsel, “Distributed Amplifier With Blue Noise active Termination,” IEEE Microwave and Wireless Components Letters, vol. 18, no. 3, March 2008.

P. K. Ikalainen, “Low-Noise distributed amplifier with active load,” IEEE Microw. Guided Wave Lett., vol. 6, no. 1, pp. 7–9, Jan. 1996.

Next time, put the post in the right section. Also, knowing the application, your specifications and what you tried so far would be helpful - also what process you are using,
Hi,
My bad for posting it in a wrong section. I'll be careful about this next time.

I never thought about the rightful terminations for LPNA. All I focused was on close to carrier noise and its properties. This was really helpful to better my understanding. I thank you for this. I am understanding, designing and comparing the noise performances of LPNA at different technologies platforms like CMOS and SiGe. Currently I'm in the first stage and I'm sure this has helped me in getting forward.

Thank You.
 

BigBoss

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"Low Phase Noise Amplifier" term is-in my opinion-wrong ..
Phase Noise is a consequence of the Noise itself and the Noise creates another result.. : AM Noise.. even-tough it's negligible..
Noise adds a fluctuation over any kind of signal even DC..So even there is a carrier or not, there should be only one single term.
Low Noise System. ( amplifier,oscillator,mixer etc.) IMHO
 

DhVJ

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"Low Phase Noise Amplifier" term is-in my opinion-wrong ..
Phase Noise is a consequence of the Noise itself and the Noise creates another result.. : AM Noise.. even-tough it's negligible..
Noise adds a fluctuation over any kind of signal even DC..So even there is a carrier or not, there should be only one single term.
Low Noise System. ( amplifier,oscillator,mixer etc.) IMHO
Hi,
I have understood that phase noise has a different mechanism compared to noise figure. The power spectral density of this noise is not flat. It depends on the offset frequency. Now, when an amplifier is considered to produce additional or residual noise to the signal which is mainly flicker noise, I would like to know how and why does this additional noise appear in the amplifier?
Could you please help me to know the theoretical/mathematical understanding of this which might help me in getting a better idea.

Thank you.
 

BigBoss

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This man is an expert on Phase Noise and he discusses how to derive math. and how to measure...
There are many papers-mostly theoretical-about the mechanism about PN.
 

    DhVJ

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Puppet123

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Yes, but he is making a MMIC distributed amplifier and the noise considerations for that are much different than those of regular analog and analog/mixed signal integrated circuits.

Just looking for references/papers on low phase noise and low noise amplifiers or LPNAs can generate a lot of information which is mostly wideband MMIC amplifiers for defense and other applications in the MMIC realm. These applications are much different than narrow band RFIC or analog/mixed signal designs. Just seach LPNA.

Thats why I originally said that this post doesnt belong in this section but in the microwave section according to the original posters intent for using this amplifier.
 

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