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Re: Need help to design a transimpedance amplifier

 

I design a lot of TIA type of amp. I don't know what kind of speed you are looking for. But your requirement is very easy, the lowest is 200nA. Any opamp with bias current of less than 10nA will work good enough.

I use LTC6268 for my design. It is likely to be way over kill for you. Check out other opamp from LT. A tip for you, I tested out a lot of opamps from Ti and Maxim. Most don't quite meet the spec on the noise even the spec say so. LT6268 really produce the result according to the spec.

Contact Glen Brisebois in LT linear opamp application group. He is very knowledgeable and helpful. I visited him in the head quarters once and he showed me a lot of tricks.
Re: Need help to design a transimpedance amplifier

 

¿ªÔÆÌåÓý

I tried to answer a couple of days ago, but it didn't come through, so I'll write it again:

The noise you observe compes from the fact that you have these big 100k resistors in the non-inverting inputs. The OPA2846 has a very high NOISE CURRENT; it is designed for low-impedance sources. There should be no resistor in the non-inverting inputs, or very low (similar to the APD's equivalent resistance); if used, this resistor should be bypassed by a capacitor, for near-zero impedance within the circuit's BW. That's VLN 101.


Le 04/08/2016 ¨¤ 09:31, t.obulesu@... [LTspice] a ¨¦crit?:
?

Let me say why am looking for new design..
We are currently using the receiver module which has three stages:
1. Trans Impedance stage
2. High Pass filter (HPF) stage
3. Unity gain amplifier (just for inverting the output of the HPF)

Well...we used LM2662 as a -5V supply..
Here on we could see the hell noise below 100kHz..
I couldn't get rid of this noise by using bypass caps..but I could just reduced it..
Yet there is a lot of noise all across the circuit ranging from few kHz to hundreds of MHz...









are the links where I have uploaded couple of documents..

I really don't know what sort of noise it is and from where it is coming...



L'absence de virus dans ce courrier ¨¦lectronique a ¨¦t¨¦ v¨¦rifi¨¦e par le logiciel antivirus Avast.


Re: "4 GROUP.zip" upload

 

I am sorry.
.MODEL BS250P ....

Bordodynov.


05.08.2016, 09:35, "§¡§Ý§Ö§Ü§ã§Ñ§ß§Õ§â §¢§à§â§Õ§à§Õ§í§ß§à§Ó BordodunovAlex@... [LTspice]" <ltspice@...>:

Hi.
.model BS170 VDMOS VTO=1.824 RG=270 RS=1.572 RD=1.436 RB=.768 KP=.1233 Cgdmax=20p Cgdmin=3p CGS=28p Cjo=35p Rds=1.2E8 IS=5p Bv=60 Ibv=10u Tt=161.6n
.MODEL BS250 VDMOS pchan Rg=160 VTO=-3.193 RS=2.041 RD=0.697 IS=2E-13 KP=0.277 Cjo=105p PB=1 LAMBDA=1.2E-2 RB=0.309 Rds=1.2E8 Cgdmax=57p Cgdmin=5p CGS=47p TT=86.56n BV=45 IBV=10u

Bordodynov.

05.08.2016, 08:56, "Andy ai.egrps@... [LTspice]" <ltspice@...>:
Jeff asked:

? ?"Is there an easy or a standard way to make a model for these transistors that can be included in LIB/cmp/standard.mos?"

For the?BS250P and BS170?transistor models you used, no, there isn't.? Those particular models are .SUBCKTs.? You can't have a subcircuit model in the "standard.mos" file.? That file is only for transistor models that use just the .MODEL syntax; it's not for subcircuits.

But aside from that .. this is a touchy question.

Aside from MS-Windows, there is nothing stopping you from editing your lib&#92;cmp&#92;standard.mos file, and adding your own MOSFET models to it if they are .MODEL models.? In fact, the LTspice Help pages even recommend it (Help: F.A.Q. -> MOSFET Models), so Mike Engelhardt thought it was OK.? Many people here in this group recommend against editing that file, but you can.

Windows might require you to be the Administrator, when you edit the file.

Of the lib&#92;cmp&#92;standard.* files, these ones are text files and could be edited directly:

standard.bjt
standard.dio
standard.jft
standard.mos

(The others are binary.)

The format is ordinary SPICE Netlist format, and should be just a .MODEL statement for each diode or transistor.? Obviously, device names must not clash, and standard SPICE rules apply about continuation lines.? Also, use only a decent text editor that does not add stray binary bytes here and there.? Notepad is best avoided.

Indeed there are enhanced versions of the standard.* files with many more transistors in them, which people have contributed to the LTspice user community.? They can be found in a few places in this group's Files area, and on the LTwiki website (ltwiki.org).

One of the problems with editing your standard.mos file (rather than pasting .MODEL statements on your schematic or having them in a separate file), is that you may forget that other LTspice users don't have those same transistors in their LTspice installation.? Then when you send them your schematic that uses one of those transistors, the schematic cannot be run.? Having those .MODEL statements separate, makes it more likely for you to send the .MODELs along with your schematic.

Regards,
Andy
Re: "4 GROUP.zip" upload

 

Hi.
.model BS170 VDMOS VTO=1.824 RG=270 RS=1.572 RD=1.436 RB=.768 KP=.1233 Cgdmax=20p Cgdmin=3p CGS=28p Cjo=35p Rds=1.2E8 IS=5p Bv=60 Ibv=10u Tt=161.6n
.MODEL BS250 VDMOS pchan Rg=160 VTO=-3.193 RS=2.041 RD=0.697 IS=2E-13 KP=0.277 Cjo=105p PB=1 LAMBDA=1.2E-2 RB=0.309 Rds=1.2E8 Cgdmax=57p Cgdmin=5p CGS=47p TT=86.56n BV=45 IBV=10u

Bordodynov.

05.08.2016, 08:56, "Andy ai.egrps@... [LTspice]" <ltspice@...>:

Jeff asked:

? ?"Is there an easy or a standard way to make a model for these transistors that can be included in LIB/cmp/standard.mos?"

For the?BS250P and BS170?transistor models you used, no, there isn't.? Those particular models are .SUBCKTs.? You can't have a subcircuit model in the "standard.mos" file.? That file is only for transistor models that use just the .MODEL syntax; it's not for subcircuits.

But aside from that .. this is a touchy question.

Aside from MS-Windows, there is nothing stopping you from editing your lib&#92;cmp&#92;standard.mos file, and adding your own MOSFET models to it if they are .MODEL models.? In fact, the LTspice Help pages even recommend it (Help: F.A.Q. -> MOSFET Models), so Mike Engelhardt thought it was OK.? Many people here in this group recommend against editing that file, but you can.

Windows might require you to be the Administrator, when you edit the file.

Of the lib&#92;cmp&#92;standard.* files, these ones are text files and could be edited directly:

standard.bjt
standard.dio
standard.jft
standard.mos

(The others are binary.)

The format is ordinary SPICE Netlist format, and should be just a .MODEL statement for each diode or transistor.? Obviously, device names must not clash, and standard SPICE rules apply about continuation lines.? Also, use only a decent text editor that does not add stray binary bytes here and there.? Notepad is best avoided.

Indeed there are enhanced versions of the standard.* files with many more transistors in them, which people have contributed to the LTspice user community.? They can be found in a few places in this group's Files area, and on the LTwiki website (ltwiki.org).

One of the problems with editing your standard.mos file (rather than pasting .MODEL statements on your schematic or having them in a separate file), is that you may forget that other LTspice users don't have those same transistors in their LTspice installation.? Then when you send them your schematic that uses one of those transistors, the schematic cannot be run.? Having those .MODEL statements separate, makes it more likely for you to send the .MODELs along with your schematic.

Regards,
Andy
Re: PWL TRIGGER syntax

 

> does somebody have problem with this syntax? PWL (0 0 1m 1 2m 1 3m 0) TRIGGER V(n003)>1
> the error msg I receieve is Unknown parameter "trigger"

Without knowing what you have, if you're using the "trigger" keyword with current sources, it doesn't work, only for voltage sources.

Vlad
______________________
-- holding, among others:
a universal analog/digital filter, block-level models
for power electronics (and not only), math blocks
with a more stream-lined approach, some digital
ADC, DAC, (synchronous-)counter, JKflop, etc.
Re: BS250 & BS170 SIM

 

Jeff wrote:

? ?"they look like they should work, but the don't, how can I add them to my CMP folder, that is what is the correct model layout."

I just noticed you sent this question two days ago.? It finally went through Yahoo's servers!? It got held up that long.

I think you already have the answer to this question.

Andy
Re: Sub circuit heat dissipation not showing

 

Brad wrote:

? ?"I hit SEND but it isn't here ?? I don't understand. Humm.."

Yup.? Yahoo was having major problems yesterday.? Hopefully that is over.? File uploads/downloads seemed to be unaffected, but messages were not.? I got a tip from elsewhere, that the larger your message, the more likely it was to get stuck, for 24 hours or more.

? ?"Basically I said I uploaded the TIP142 sub circuit?..."

I am not seeing that.? It's not in "Temp", and there is no file upload listed for you from the last two days (or ever).? Are you sure you uploaded it to this group?? File uploads didn't get delayed, so if you uploaded it and did not get an error message right away, it would be here.

It would be good to see the simulation you have that has this problem.

I am a bit confused about your references to the formula versus the value.? Are you looking for a graph of power dissipation versus time?? To graph power, LTspice uses a formula of pin currents and voltages.? You will see that formula at the top of the plot window, but you should also see the plot, from that formula, within the plot window.? There is a separate action to integrate the area under a plot.? Did you do that?

Help page: Waveform Viewer -> Data Trace Selection
... and then look about half-way down that page.

? ?"BTW. What is the Poll button about??"

Yahoo!Groups allow group-wide polls, or votes, where members get to "cast their ballot" by choosing one or more choices.? They are not particularly useful here.? I do not recommend them.? If you have a specific idea in mind, please first send them in an email to the group's Moderators (ltspice-owner @ ).

? ?"Also how do I get emails just on this conversation and not all the others in the LT Spice group."

Sorry, it's all or nothing.? Yahoo doesn't filter what it sends you.

But you have the perfect email service (Gmail) where you can do the filtering on your end.

You can direct all the messages from this group to somewhere other than your Inbox ("Archive" them), and then they won't clutter your Inbox anymore.

The other option you have is to select Daily Digest emails instead of Individual Emails.

Andy
Re: LTspice IV (NOT RESPONDING)

 

There is one thing I can do with LTspice on my home computer that causes Windows to think it is not responding.? If I turn on Mark Data Points in the waveform display, and if the density of points is high enough, LTspice takes a VERY long time re-drawing the screen over and over and over again (infinite loop?).? I guess it might be an interaction with the display driver, and maybe LTspice times out and starts over, repeatedly.? When this happens, I can sometimes stop it, but most of the time the only thing I can do is go to the Windows Task Manager and kill LTspice.

So I hesitate to call this just a Windows thing.

Andy

?
Re: PWL TRIGGER syntax

 

Hello,

The 32 bit version of LTspiceXVII had a problem with PWL in early versions.
Do you use the 32 bit version LTspiceXVII.exe(x86)??

Please update LTspiceXVII to the latest version.

Tools > Sync release

Best regards,
Helmut
Re: "4 GROUP.zip" upload

 

Jeff asked:

? ?"Is there an easy or a standard way to make a model for these transistors that can be included in LIB/cmp/standard.mos?"

For the?BS250P and BS170?transistor models you used, no, there isn't.? Those particular models are .SUBCKTs.? You can't have a subcircuit model in the "standard.mos" file.? That file is only for transistor models that use just the .MODEL syntax; it's not for subcircuits.

But aside from that .. this is a touchy question.

Aside from MS-Windows, there is nothing stopping you from editing your lib\cmp\standard.mos file, and adding your own MOSFET models to it if they are .MODEL models.? In fact, the LTspice Help pages even recommend it (Help: F.A.Q. -> MOSFET Models), so Mike Engelhardt thought it was OK.? Many people here in this group recommend against editing that file, but you can.

Windows might require you to be the Administrator, when you edit the file.

Of the lib\cmp\standard.* files, these ones are text files and could be edited directly:

standard.bjt
standard.dio
standard.jft
standard.mos

(The others are binary.)

The format is ordinary SPICE Netlist format, and should be just a .MODEL statement for each diode or transistor.? Obviously, device names must not clash, and standard SPICE rules apply about continuation lines.? Also, use only a decent text editor that does not add stray binary bytes here and there.? Notepad is best avoided.

Indeed there are enhanced versions of the standard.* files with many more transistors in them, which people have contributed to the LTspice user community.? They can be found in a few places in this group's Files area, and on the LTwiki website ().

One of the problems with editing your standard.mos file (rather than pasting .MODEL statements on your schematic or having them in a separate file), is that you may forget that other LTspice users don't have those same transistors in their LTspice installation.? Then when you send them your schematic that uses one of those transistors, the schematic cannot be run.? Having those .MODEL statements separate, makes it more likely for you to send the .MODELs along with your schematic.

Regards,
Andy
Re: high frequency MHz and GHz range BJTtransistor or Mosfet

 

The major problem with tuned RF design is you don't know where the optimize point is for minimum reflection and maximum power transfer. You have 3 variables, L, R and C and you have more than one optimized point depends on what is the other requirements. Smith Chart show you in graph every single point so you can choose the RLC values at the same time. It can get very complicated to vary 3 values in LTSpice.

In another words, LTSpice is good if you know the values and see what is the outcome. But it is not good if you are searching for the optimize values of 3 components or more.

Now, for wide band circuits, Smith Chart is useless. I think that's where LTSpice shines.

Bottom line, I think it's the "iteration" thing that's where Smith Chart simulation is strong.
Re: high frequency MHz and GHz range BJTtransistor or Mosfet

John Woodgate
 

¿ªÔÆÌåÓý

LTspice is good up to frequencies where you need to use distributed elements, which I suppose is about 1 GHz. It's not intended to be an optimiser. Is there anything a Smith chart can do that LTspice matrix methods cannot?

?

With best wishes DESIGN IT IN! OOO ¨C Own Opinions Only

J M Woodgate and Associates Rayleigh England

?

Sylvae in aeternum manent.

?

From: LTspice@... [mailto:LTspice@...]
Sent: Thursday, August 4, 2016 5:34 PM
To: LTspice@...
Subject: [LTspice] Re: high frequency MHz and GHz range BJTtransistor or Mosfet

?

?

This is not exactly relate to the original question. My question is how useful is LTSpice for RF design? I was an RF engineer, we use Microwave Office and using Smith Chart for matching and gain. I don't see LTSpice can help much in designing RF circuits(tuned circuit). Particularly when use start using distributed elements ( using stripline or microstrip to simulate inductors and capacitors).

I am sure LTSpice can give you the answer if you fill in the values of the L R C, but it will not help you in optimizing the circuit which is the key for RF circuit. But you cannot guess the values.

I use LTSpice for RF transistors only for wide band circuits where smith chart is not particularly useful.
Re: high frequency MHz and GHz range BJTtransistor or Mosfet

 

This is not exactly relate to the original question. My question is how useful is LTSpice for RF design? I was an RF engineer, we use Microwave Office and using Smith Chart for matching and gain. I don't see LTSpice can help much in designing RF circuits(tuned circuit). Particularly when use start using distributed elements ( using stripline or microstrip to simulate inductors and capacitors).

I am sure LTSpice can give you the answer if you fill in the values of the L R C, but it will not help you in optimizing the circuit which is the key for RF circuit. But you cannot guess the values.

I use LTSpice for RF transistors only for wide band circuits where smith chart is not particularly useful.
Re: high frequency MHz and GHz range BJTtransistor or Mosfet

 

....for those of you new to "BJT land", I found this little tidbit* on youtube:






No Helmut they didn't have the German version (that I could locate anyway).


W. Warren

*( figured this website would appreciate this stuff, other sites I might have posted this on would have
??? barred me for spamming ; )

?
Re: high frequency MHz and GHz range BJTtransistor or Mosfet

 

¿ªÔÆÌåÓý

yes, but that¡¯s the can.

The mmbt918 in sot23 is in stock @ 4?@3k.? Much better deal than ?4.

?

?

?

From: LTspice@... [mailto:LTspice@...]
Sent: Wednesday, August 03, 2016 11:47 PM
To: LTspice@...
Subject: Re: [LTspice] high frequency MHz and GHz range BJTtransistor or Mosfet

?

?

Frank Mead wrote:

"The 2n918, 2n5179, and the 2n2857 are still alive and well in Mouser database...

they are still used..."

?

Indeed they are listed. But did you check the prices and availability? At ?4 each for a 2N918, nobody's going to design it into anything; these are for maintenance only - mostly for military, and Central Semi are not the original manufacturer. They buy rights to old devices when discontinued by their originators. They're obsolete in the same sense as KT66s. [Stands back and awaits flames. ?:-) ?]

?

Regards,

Tony

?
Re: Sub circuit heat dissipation not showing

 

Hello,

>?Helmut thanks for your answer. Much appreciated. Unfortunately, last night I replied with a detailed answer. I hit SEND but it isn't here ?? I don't understand. Humm..

I also miss two of my messages regarding AD830 from last night. They are still not there. It seems Yahoo had a problem last night.?


>?BTW. What is the Poll button about??

There was a new poll a few days ago. I have deleted this poll, because it looked useless.
There were two other polls which I had deleted before, because I read somewhere that the problem with list by "topics" could have to do with polls. Finally I found this is not true. The topics problem?is independent

Best regards,
Helmut
?
Re: "4 GROUP.zip" upload

 

PERFECT ANSWER!!! (shouted)?I appreciate the explanations, I will copy and save it for periodic reference I when screw up again.
I'm sure I typed my message, but not sure I sent it or I did and yahoo went weird on me. Maybe my shout was loud enough in the upload to be heard in messages :) no!! ? You did very good by me ?and I thank you.
Is there an easy or a standard way to make a model for these transistors that can be included in LIB/cmp/standard.mos?
Jeff
Re: Sub circuit heat dissipation not showing

 

Helmut thanks for your answer. Much appreciated. Unfortunately, last night I replied with a detailed answer. I hit SEND but it isn't here ?? I don't understand. Humm..

Basically I said I uploaded the TIP142 sub circuit and I get a dissipation plot but not the power dissipation value. For that matter R2 doesn't even have dissipation value. I think in my original post I point out that the value (not the only the formula) is what I was looking for.

Very frustrating that I typed such a detailed answer last night but it's not here! I'm at work so that about all the time I have.

BTW. What is the Poll button about??

Also how do I get emails just on this conversation and not all the others in the LT Spice group. I must admit this group is very informative though. I just didn't want to fill up my mailbox.

Thanks Again, Brad
PS) hopefully this post will make it through!!


---In LTspice@..., <helmutsennewald@...> wrote :

Hello,

The power dissipation of the TIP142 from our Files section will be correctly displayed.
TIP_142_test.zip

??

Here are a few more examples. Their power will be displayed too.


All the Darlington transistors in my examples correctly plot power.?

In therory there are subcircuits possible where LTspice doesn't plot the power due to special combinations of sources internally connected to the pins of a subcircuit.

You should upload your files for a test.

Best regards,
Helmut

?

?
Re: Henry's current transformer problem

[email protected]
 

Andy and analogspiceman

Thank you for your replies.

Actually, I am not sure what I was thinking for the path length = Ie!

It should of course be Pi * D where D = (Internal Diameter + External Diameter)/2.

Hence for my figures it is about 71.47mm, so Lm is 71.47m.

Also I now realise that LTSpice has Hc specified in A/m and the Information I found for typical ferrites was 0.2 Oesteds which is about 15.9 A/m. So Hc for LTSpice = 15.9.

I appreciate that there is a lot of variation in ferrite materials, but I am just trying to use a typical one that could be used for a Current Transformer, as I do not know which specific one has been used.

Having clarified the above, I have one more question.

Do you have any knowledge of how the actual VA of the Burden Resistor used versus the VA rating of a Current Transformer affects the accracy of the resuting Voltage?

My thinking is that the higher the VA through the Burden and hence the Current Transformer's secondary coil, the hotter it gets and hence this affects the resulting Voltage as the core's magnetic properties dictate.

Would that be correct or can you offer any more insights and/or provide any links to sources of information about this topic?

Thanks and Regards
Henry Kafeman

---In LTspice@..., <ai.egrps@...> wrote :

Henry wrote:

? ?"I now believe the core of the CT is "ferrite"."

?FYI -- ferrites encompass a whole class of materials, with a widely varying range of magnetic characteristics.? Ferrites are often used as cores for "ferrite beads", chokes, and transformers, and there are many ferrite materials (or "mixes") to choose from.

Andy
Re: Need spice model for IR TX and RX

 

...best* I can do Dhanabal:

?? <---data sheet

? <--SPICE and related modeling software at site


W. Warren

*(See if there is a usable model already in LTSPICE similar to those devices, then "substitute values",

or ask around here for help with 'maybe a PSPICE model?? You could always send the manufacturer

an email request.)
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