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Old 27th February 2008, 08:03 PM   #501
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Default Simulators

Hi Fotios.

If someone lacks the skill to use simulators properly, doesn't mean they are useless.

Cheers.
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Old 27th February 2008, 10:06 PM   #502
fotios is offline fotios  Greece
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Default Re: Simulators

Quote:
Originally posted by Edmond Stuart
Hi Fotios.

If someone lacks the skill to use simulators properly, doesn't mean they are useless.

Cheers.
Hi Edmond and glad to meet you

Of course the simulators aren't uselles. Moreover this evidence their existence from alone. Personally me, i have occupied for 1 to 2 years with these and as i wrote in my post i use these in some measurements to avoid the tiring replacement of resistors untill i have success in my project. My philosophy it is that: For so small size projects such as the audio devices which is the subject of this forum why we need an extensive spice simulation? On the other hand, in big projects such aerodynamics the simulation it is needfull because the cost of materials used is very big for making experiments. For a small thing such an amplifier we can draw the theoretical scheme, we can compute approximatelly the values of resistors and thus the currents, we can make a prototype board and with the aid of an oscilloscope we can finally to finish our project by testing it by changing the values of few resistors and maybe one or two caps. We don't have to discover a new thing. All the topologies are shared in all of people. A big changing can be done only if someone factory of semiconductors discovers a new material with better capabilities from the silicon doppings. Personally i am with you who read books and books and i test everything new because my big curiosity. But i have an objection; a thread started for a discussion and oppinions about a concret subject, it becames (as usually happens in this forum) in exchanges of data between the members - also me am not excluded from such situations - and the debate that placed in the begining J. Curl has lost its mean between so much pages inluding endless lists of spice elements data exchanged via the vast majority of posts. You can understand my place? I had a little long time to read the forum because other obligations and surprisingly i read this thread as permanent with a subject about it i have a view. What can i firstread into this babel of posts?

I ask the comprehension of all the obvious educated persons in this thread

With respect to you and your knoweledge
Fotios Anagnostou
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Old 27th February 2008, 10:29 PM   #503
gootee is offline gootee  United States
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Quote:
Originally posted by anatech

quote (gootee):
We also need to get some magazines, like EDN et al, to write articles that could help convince the manufacturers that having spice models (and good spice models, at that) might _INCREASE SALES_ of their components.


Hi Tom,

Contacting EDN is an excellent idea. Since great expense was expended making the simulators available to the world, some effort in producing models seems reasonable.

This actually sounds like an interesting series of articles for EDN to run, and they are hitting their target audience.

-Chris
Having almost forgotten about this, I finally emailed Ron Mancini, of Texas Instruments, who did an article for EDN about spice models, which is here: http://www.edn.com/article/CA633459.html , giving him the basic idea, and the link for this thread, and asking him whom I should contact, to encourage that this be done, etc etc.

I will let you know, if I receive a reply.
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Old 27th February 2008, 11:05 PM   #504
andy_c is offline andy_c  United States
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Default Re: Re: Simulators

Quote:
Originally posted by fotios
But i have an objection; a thread started for a discussion and oppinions about a concret subject, it becames (as usually happens in this forum) in exchanges of data between the members
Hi Fotios,

Let me try to explain the history of how this thread came about.

A few months ago, several members of the forum found that many of the threads they were participating in kept getting derailed by discussion of various SPICE topics. The idea came up of having a sticky thread devoted to SPICE tips and tricks, SPICE model development, requests for models and general SPICE help. This idea was brought up to one of the moderators, who agreed to make a sticky thread. One (or maybe more) of the moderators removed some SPICE-specific posts from several different threads that were going on at the time, and combined them to form the beginning of this thread. John's post ended up appearing first, so it looks like he started the thread, rather than what really happened.

One unfortunate side effect of this is that the first post sets the tone of the thread, making it look like it was intended as a debate about SPICE. But that was not the reason for this thread's existence at all. Basically the thread begins with an off-topic post - not exactly what someone not familiar with the situation would expect!
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Old 28th February 2008, 09:27 AM   #505
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Default off topic

Quote:
Originally posted by fotios
Hi Edmond and glad to meet you
[snip]
My philosophy it is that: For so small size projects such as the audio devices which is the subject of this forum why we need an extensive spice simulation?
[snip]
For a small thing such an amplifier we can draw the theoretical scheme, we can compute approximatelly the values of resistors and thus the currents, we can make a prototype board and with the aid of an oscilloscope we can finally to finish our project by testing it by changing the values of few resistors and maybe one or two caps. We don't have to discover a new thing. All the topologies are shared in all of people.
[snip]
With respect to you and your knoweledge
Fotios Anagnostou
Hi Fotios,

With all respect, but I disagree with you on several points:

Not all amplifiers are that small. Take for example our PGP amp, some 233 components, auxiliary circuits not counted.

There are new thing to discover. Again, take our our PGP amp: a new nested differential feedback loop (NDFL), a common mode control loop (CMCL) and a nested feedback clamp. All new, never published before. We had to test these new ideas by simulating them first. I dare to say that without a simulator, it was almost impossible to design the PGP amp.

Furthermore, some important details, like the phase and gain margin of a Miller loop, are not easily assessed with hardware. Here, a simulator comes at rescue.

And finally, it's highly recommended to capture the schematic and generate a net-list for the PCB artwork. So, it's quite logical to use the already captured schematic also for simulation. Admittedly, not all design errors will be revealed in this way, but gross errors will certainly be detected, saving you a redesign of the PCB.

BTW, opposed to designing with a solder iron and oscilloscope, designing with a simulator is an art in his own right. You have to develop a feeling when the simulator is lying, about the Early effect for example. So, what to do? Simply eliminate this effect by means of a cascode or bootstrapping.



Cheers, Edmond.

To all, sorry to be off topic.
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Old 28th February 2008, 11:23 AM   #506
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Default Re: off topic

Quote:
Originally posted by Edmond Stuart


Hi Fotios,

With all respect, but I disagree with you on several points:

Not all amplifiers are that small. Take for example our PGP amp, some 233 components, auxiliary circuits not counted.

There are new thing to discover. Again, take our our PGP amp: a new nested differential feedback loop (NDFL), a common mode control loop (CMCL) and a nested feedback clamp. All new, never published before. We had to test these new ideas by simulating them first. I dare to say that without a simulator, it was almost impossible to design the PGP amp.

Furthermore, some important details, like the phase and gain margin of a Miller loop, are not easily assessed with hardware. Here, a simulator comes at rescue.

And finally, it's highly recommended to capture the schematic and generate a net-list for the PCB artwork. So, it's quite logical to use the already captured schematic also for simulation. Admittedly, not all design errors will be revealed in this way, but gross errors will certainly be detected, saving you a redesign of the PCB.

BTW, opposed to designing with a solder iron and oscilloscope, designing with a simulator is an art in his own right. You have to develop a feeling when the simulator is lying, about the Early effect for example. So, what to do? Simply eliminate this effect by means of a cascode or bootstrapping.



Cheers, Edmond.

To all, sorry to be off topic.

Hi Edmond,

I agree completely. The performance of new and sometimes more complex designs would be difficult to evaluate (and optimize) without SPICE. I even find it valuable for smaller designs, especially in cases where the circuit topology is a bit unusual. Although you rightly point out that we have to be careful about what we trust from SPICE and do not trust from it, it can also be very valuable in evaluating the local stability of circuits, especially when we want to insert some speculative wiring inductances.

SPICE is no substitute for building a prototype, measuring it and listening to it, but few if any here have ever suggested that. It is a very valuable tool in a tool box with numerous tools.

Cheers,
Bob
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Old 28th February 2008, 12:04 PM   #507
fotios is offline fotios  Greece
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Default Re: Re: off topic

Quote:
Originally posted by Edmond Stuart


Hi Fotios,

With all respect, but I disagree with you on several points:

Not all amplifiers are that small. Take for example our PGP amp, some 233 components, auxiliary circuits not counted.

There are new thing to discover. Again, take our our PGP amp: a new nested differential feedback loop (NDFL), a common mode control loop (CMCL) and a nested feedback clamp. All new, never published before. We had to test these new ideas by simulating them first. I dare to say that without a simulator, it was almost impossible to design the PGP amp.

Furthermore, some important details, like the phase and gain margin of a Miller loop, are not easily assessed with hardware. Here, a simulator comes at rescue.

And finally, it's highly recommended to capture the schematic and generate a net-list for the PCB artwork. So, it's quite logical to use the already captured schematic also for simulation. Admittedly, not all design errors will be revealed in this way, but gross errors will certainly be detected, saving you a redesign of the PCB.

BTW, opposed to designing with a solder iron and oscilloscope, designing with a simulator is an art in his own right. You have to develop a feeling when the simulator is lying, about the Early effect for example. So, what to do? Simply eliminate this effect by means of a cascode or bootstrapping.



Cheers, Edmond.

To all, sorry to be off topic.

Quote:
Originally posted by Bob Cordell



Hi Edmond,

I agree completely. The performance of new and sometimes more complex designs would be difficult to evaluate (and optimize) without SPICE. I even find it valuable for smaller designs, especially in cases where the circuit topology is a bit unusual. Although you rightly point out that we have to be careful about what we trust from SPICE and do not trust from it, it can also be very valuable in evaluating the local stability of circuits, especially when we want to insert some speculative wiring inductances.

SPICE is no substitute for building a prototype, measuring it and listening to it, but few if any here have ever suggested that. It is a very valuable tool in a tool box with numerous tools.

Cheers,
Bob
To be more comprehensible, how much accurate can be a spice simulation for this circuit:

http://www.diyaudio.com/forums/attac...amp=1173212907

And below it is the spice model of it ready for you:

http://www.diyaudio.com/forums/attac...amp=1173773152
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Old 28th February 2008, 02:18 PM   #508
syn08 is offline syn08  Canada
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Default Re: Re: Re: off topic

Quote:
Originally posted by fotios


To be more comprehensible, how much accurate can be a spice simulation for this circuit:

http://www.diyaudio.com/forums/attac...amp=1173212907

And below it is the spice model of it ready for you:

http://www.diyaudio.com/forums/attac...amp=1173773152
Simulating what?

Don't let the number of trannies fool you. It's essentially a classic circuit, already analyzed to death. Even the THD (if that's what you are looking for) can be estimated by simply inspecting the schematic and having some previous data regarding the open loop THD vs. the output stage bias, for a particular set of output devices.

I think you just hit one of the simulation major traps. Relying on simulations without having some understanding of the circuit functionality is a pretty safe recipe for disaster. Simulation is a tool for the already illuminated - it may deliver (more or less precise) what you are looking for but it won't tell you straight what to look for.
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Old 28th February 2008, 10:13 PM   #509
fotios is offline fotios  Greece
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Default Re: Re: Re: Re: off topic

Quote:
Originally posted by syn08


Simulating what?

Don't let the number of trannies fool you. It's essentially a classic circuit, already analyzed to death. Even the THD (if that's what you are looking for) can be estimated by simply inspecting the schematic and having some previous data regarding the open loop THD vs. the output stage bias, for a particular set of output devices.

I think you just hit one of the simulation major traps. Relying on simulations without having some understanding of the circuit functionality is a pretty safe recipe for disaster. Simulation is a tool for the already illuminated - it may deliver (more or less precise) what you are looking for but it won't tell you straight what to look for.
The concrete circuit it is not of Hi-End classs, as i suppose that you are thinking so i am thinking for it. It is obviously armed for hard working in P.A. applications. On the contrary of your statement that it is for death, it is checked in practice and it works just fine.
In the spice model that i quote, the only that i try to estimate it is the values of static currents (because their correct values are very significant for the exploitation of the plentiful dynamics which offers this amplification arrangement) so don't be harry in your conclusions. You can calculate very easy their values with the aid of voltage drop markers in the different locations. For this purpose the spice gives by 90% correct results for practical use (because the 1% MF resistors used and only for this). Also i don't use the time domain analysis of simulator to estimate something. The only diagram which i take it is the output power level under different loads (and this is indicated satisfactory by simulation because the output load it is supposed clear resistive) so i can set the values of the output VI limitter circuit resistors summing network to place a limit down to 2 Ohms for activating it. Concretely i modify the values of resistors so the current calculated via the voltage drop accross each emitter resistor, does not exceed the 1,5A per output device so it remains into the SOA given from Motorola.
Because as i suspect you are Mosfet fun, by debate this bipolar implementation with any Mosfet (i bet anything you thing that you can get easy from me by eliminating the obstacle of distance of our places) maybe you revise your thoughts for this "paleolithic" amplification circuit "with its one foot already into the grave". In a previous thread i gave a complette documentation with curves from DSO. You can search it in the forum or in my web page. I refer only that its rise time vary between 1,3ýsec up to 100W/8┘ and 2,3ýsec up to 350W/8┘ with the Miller pole strongly compensated (limitting thus its bandwidth up to 100KHz). My experience showed me that the big power projects of class AB can beat easy each Mosfet or class A project due to its dynamics. This project it is not a toy of 2X100W.
This project also it is not a copy (a CLONE as you like to say in this forum) of the design of anyone. It is the result of my research for many years and the implementation of different topologies in one design for my concrette demands.
Finally this project because the extremely high supply voltage used (up to 170Vpp) i suggested in my thread only in skill full persons because any accidental shorting during setup can causes a big BANG! with catastrophic results so in the devices as in the PCB.

I ask your forgiveness if this reply it is off topic of the concrete thread


Fotios Anagnostou
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Old 28th February 2008, 11:19 PM   #510
fotios is offline fotios  Greece
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Default Re: Re: Re: Re: off topic

Quote:
Originally posted by syn08


Simulating what?

Don't let the number of trannies fool you. It's essentially a classic circuit, already analyzed to death.
Hi syn08

I ask your forgiveness if i misinterpreted your phrase "already analyzed to death". I translated it as "already analyzed FOR death". I don't know English very well. If the sense of your phrasing it is indeed as i supposed, then my previous reply it is in effect.
However, many times a person state his phrase in a wrong way. So, i can suppose also that the sense of your phrase it is "already analyzed UP TO death" or "already analyzed UNTIL death". You can see that only and only one wrong word can cause a whole debate, and you can't reproach me if this is true.
In our country, we are very careful when we speak or when we write because the complexity of our language and the decuple lot of words which contains from each other language, which drive many times in ambiguous meanings. Be careful to not involved with a Greek lawyer or law!!!
From the other hand (in Greek language we say the same as "from the other side" always and this is correct; what relation has a hand with the phrasing of a phrase?) i think also that my post #507 it is not out of the topic because indeed presents a spice simulation process named "Initial Voltages Guess" if i remembered well from my EDSpice simulator.

With each respect to you, but unhesitating also for each debate with you.

Fotios Anagnostou
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