In LTspice you can get the contribution of any component you like in the plot of noise over frequency. No need to study the chain printer output.
A few weeks ago I downloaded a new 4898 model that is much better than the one I used b4.
cheers, Gerhard
Am 17.02.2018 um 09:21 schrieb Kevin Aylward:
In LTspice just plot onoise(R1) / gain to get it scaled to the input
Oscillator phase noise is not bizarre at all. It is just that Spice cannot handle nonlinear noise analysis. Harmonic balance analysis is missing.
Spice calculates noise in the linearized circuit at the operating point. But oscillators are inherently nonlinear since they need a limiting mechanism or they would go super nova after some time. (Or not oscillate at all.)
During each part of the oscillation cycle the OP is different, gain is different, contributions are different.
So you need a harmonic balance simulator, as available in ADS or in Microwave Office and the models for it.
I also cannot simulate the noise behavior of my chopper amplifier. In what state of the input switches should it be analyzed? :-(
cheers, Gerhard
I thought that it was referred to as 'resonance'.
Am 17.02.2018 um 09:21 schrieb Kevin Aylward:
Missed the point.
I said an *ordered* *list*, for example
Component Noise Report at Frequency = 10Hz
"Rank" "Ref Des" "Noise (V/sqrtHz)" "Contribution"
1 qn1 1.80771u 63.7807 % 2 qn1_1f 1.80249u 63.096 % 3 qn2 485.026n 3.1778 % 4 qn2_1f 434.741n 2.54486 % 5 r3 341.859n 1.56584 % 6 qn4 328.451n 1.44454 % 7 qn4_1f 248.531n 824.51m % 8 qn2_rb 201.111n 539.12m % 9 qn4_rb 200.766n 537.269m % 10 qn3 182.546n 443.968m % 11 qn3_1f 161.473n 347.213m % 12 qn1_ib 104.411n 145.027m % 13 qn3_rb 76.5087n 77.8453m % 14 qn1_rb 76.4419n 77.7093m % 15 qn4_ic 73.1846n 71.2255m % 16 qn2_ic 70.1976n 65.5281m % 17 qn1_ic 45.3065n 27.2912m % 18 qn3_ic 35.6833n 16.928m % 19 qn2_ib 25.1827n 8.43072m % 20 qn2_re 15.5829n 3.22808m % 21 qn4_re 15.5567n 3.21723m % 22 qn4_ib 14.3964n 2.75519m % 23 qn3_ib 9.35346n 1.16302m % 24 r2 8.44238n 947.487u % 25 qn3_re 5.92827n 467.194u % 26 qn1_re 5.92339n 466.425u % 27 r4 3.89178n 201.344u % 28 r5 1.86634n 46.3044u % 29 r1 286.521p 1.09132u % 30 qn4_rc 9.83235p 1.28516n % 31 qn2_rc 8.91246p 1.05593n % 32 qn1_rc 4.05183p 218.248p % 33 qn3_rc 3.51699p 164.435p %Total Output Noise 1.93939u
Yes it is, when compared to amplitude noise.
Some of us have actually done 10,000s of phases simulations over the last 10 years...and produced product to boot...
Granpas.. Suck eggs.....teach....don't...
and you typically, need something like Shooting Method when the system is highly non-linear.
-- Kevin Aylward
Good oscillators generally have ALC, though, so the self-limiting behaviour isn't such an issue with simulations (at least outside the ALC bandwidth).
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
Sure. I do that commonly. I just wish that "gain" were the same as V(onoise)/inoise, which it isn't--the units come out scrambled so you get multiple vertical axes that autoscale independently.
Thus I'm always plotting stuff like
V(Q1)*V(onoise)/inoise
and shot noise limits as
1A*sqrt(3.2e-19*1u/1Hz)to get the units to come out right, because LTspice's plotting code is too stupid to know that 1V/1A = 1 ohm.
Where did you get it? Could you shoot me a copy?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
Does it work for subcircuits? One irritation in LTspice is that you can't readily plot the noise contribution of op amps or even of transistors if their models include parasitics (and so have to be subcircuits).
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
(wrong way up)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
[snip]
Can you show me how that works? I haven't been able to figure that out.
Maybe a *.asc example that prints out a noise report?
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
It's what you learn, after you know it all, that counts.
View -> SPICE netlist
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net https://hobbs-eo.com
OK. That works. But fails to show me the actual model used. Therein is the prevarication.
That's _not_ an asc file.
Why did you snip "Maybe a *.asc example that prints out a noise report?" from my post?
.MEAS is as useless as t*ts on a boar hog. Are you going to manually measure each component individually... including all the device parameters to locate a critical noise source? Gimme a break... there can be hundreds.
So LTspice _doesn't_ print out a noise report? And you can't provide an asc example that does?
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
It's what you learn, after you know it all, that counts.
ave a .NET
tcal_Quantities
So what?
e can be hundreds.
e an asc exam
I was trying to help out--if you're just looking for reasons to hate LTspic e, please have at it on your own. I have no interest in such reports myself
--the plot facility is good enough.
Cheers
Phil Hobbs
I'm just the administrator of the truth serum >:-}
Glad you're a happy camper. Without a noise report (device-level) optimizing an amplifier would be a bitch.
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
It's what you learn, after you know it all, that counts.
Yes. A typical opamp circuit will get you :
Component Noise Report at Frequency = 10Hz
"Rank" "Ref Des" "Noise (V/sqrtHz)" "Contribution"
1 r2 40.7136n 31.4283 % 2 r:X1:c2 20.8671n 7.2192 % 3 r:X1:c1 20.8671n 7.2192 % 4 q:X1:1 14.7515n 3.5402 % 5 q:X1:1_ic 14.7353n 3.53227 % 6 q:X1:2 14.7277n 3.52854 % 7 q:X1:2_ic 14.7277n 3.52854 % 8 r1 12.8748n 2.68501 % 9 q:X1:1_ib 692.029p 7.65353m % 10 r:X1:e1 104.023p 172.923u % 11 r:X1:e2 104.023p 172.923u % 12 d:X1:ln_id 6.15178p 604.782n % 13 d:X1:ln 6.15178p 604.782n % 14 d:X1:lp_id 6.15178p 604.781n % 15 d:X1:lp 6.15178p 604.781n % 16 d:X1:e_id 2.39867p 91.947n % 17 d:X1:e 2.39867p 91.947n % 18 d:X1:c_id 2.39857p 91.9395n % 19 d:X1:c 2.39857p 91.9395n % 20 r:X1:2 728.675f 8.48526n % 21 r:X1:ee 85.7994f 117.65p % 22 q:X1:2_ib 46.2129f 34.1283p % 23 r:X1:o1 14.4329f 3.33067p % 24 r:X1:o2 4.72999f 355.271f %The ordered list is really useful in knowing where the main problems are. Note that there is an option to chose what frequency that the order is done for.
Someday I might rationalise the X naming convention, as it's shit as is.
-- Kevin Aylward
ADA4528: noise peak at 200 kHz but otherwise well behaved. 2.2-5.5V supply.
I'm also using an LT6655-2.5 as a (DAC) reference - seems to have the similar no 1/f with a noise peak characteristic. 6-8 uF on the output flattens the noise nicely.
-- Grizzly H.
That depends on the gain control mechanism. In general Wien bridge oscillat ors use gain control elements that are close to linear over the oscillation cycle.
Jim Williams used a FET as his gain adjustment mechanism, and it's resistan ce would stay the same over the oscillation cycle, and you could change the resistance by changing the gate voltage (which was a lot bigger than the sinusoidal voltage at the FET, and you can AC-couple that sinusoidal voltag e into the gate bias voltage if you are feeling perfectionist).
see figure 45 on page 31.
-- Bill Sloman, Sydney
Looks like an interesting reference. How low does that "no 1/f" behaviour go?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Nope. The gain control is not the only active device. For xtal oscillators, there is usually no specific gain limiter. There just limit by voltage or current starvation.
I think you are missing the point. Its not just one device, say operating over an approximate constant resistance noise. All active devices are nonlinear. For example, consider a main amplifying transistor. Its collector current noise is sqrt(2.IC.q) and its base current noise sqrt(2.q.ib). This noise is changing over the whole cycle as the transistor goes from cutoff to full on.
Phase noise tools determine the steady state solution i.e. the PSS Periodic Steady State, and use this solution to calculate the Phase Noise on a point by point bases over the the whole waveform.
It matters.
-- Kevin Aylward
Am 17.02.2018 um 16:56 schrieb Phil Hobbs:
No, not at all generally. It is easy to spoil a lot and the advantage is small in reality.
But I do have a design that works well.
cheers, Gerhard
Don't know for certain. I'm not tooled to measure it directly. It's all part of a control loop to stabilize a magnetic field to ~ 1 ppm (NMR magnetometer). Temperature is the primary driver but our oven wanders around about 0.1C which is also resolution of the system's temperature measurements. We can see doors opening and A/C cycling when the system is in the oven. The measured temps correlate with the correction currents within a ppm or two over hours so there's no evidence that the reference is worse than that.
-- Grizzly H.
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.