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 OpAmp Simulation in Cadence Spectre 

Last post Mon, Apr 7 2014 4:44 AM by HamidKhatibi. 19 replies.
Started by Shahnaf 03 Nov 2011 08:49 AM. Topic has 19 replies and 9615 views
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  • Thu, Nov 3 2011 8:49 AM

    • Shahnaf
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    • Joined on Mon, Aug 29 2011
    • Posts 14
    • Points 265
    OpAmp Simulation in Cadence Spectre Reply
    Hi, I have used OpAmp symbol from Solutions library (default library of cadence). As an initial step, I have simulated a basic circuit in Op Amp. But I am not getting the desired output. Moreover, I have checked the cadence simulation manual for Op Amp. I found something difference in the symbol (from Solutions library) to that of the Cadence manual. Can you please let me know where I am wrong and what needs to be corrected? Thanks, Shahnaz
    • Post Points: 35
  • Thu, Nov 3 2011 11:38 AM

    Re: OpAmp Simulation in Cadence Spectre Reply

    Shahnaz,

    Please read the Forum Guidelines.  There are so many things that are undefined, that it's hard for anyone to answer:

    1. Which "Solutions" library? The only library I can find is in <ICinstDir>/tools/dfII/samples/artist/solutions (note it's in lower case). This contains a cell called ampTest but it doesn't look the same as the one you posted a picture of (hard to tell, because it's rather a small bitmap).
    2. Which version are you using?
    3. Which "Cadence simulation manual" are you talking about. I can't find any reference to this. Is it a Cadence manual, or one from some University course?
    4. You're not getting the desired output - what is your desired output, and what did you actually get?
    5. I'm not sure what you mean by "As an initial step, I have simulated a basic circuit in Op Amp". What does "simulating a basic circuit in Op Amp" mean?

    If you don't ask clear and precise questions, it's unlikely you'll get a clear and precise answer, unfortunately. I'd love to be able to help you, but hard to with insufficient information!

    Best Regards,

    Andrew.

    • Post Points: 35
  • Thu, Nov 3 2011 10:44 PM

    • Shahnaf
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    • Posts 14
    • Points 265
    Re: OpAmp Simulation in Cadence Spectre Reply

     Hi Andrew,

    I am using Cadence Virtuoso version 6.1.5. In this version, I still find "Solutions" library which is the default library given by cadence.

    I have attached the snapshot of the Solutions library which is the first menu of the Library manager.

    The desired output for the attached circuit is V0 = (R2/R1) *  V1. 

    Since R2 is 1K ohm and R1 is 100 ohm, the expected output is 10 times the input. But I got some different output.

    My intention is to use the Opamp as a linear multiplier. I had n't used Opamp in my earlier designs and this is the first time i had used.

    So, I started with the basic circuit of Opamp as a voltage amplifier.

    I am unable to attach the snapshots or image here. I will mail you to your id.

     

    Thanks!

     


    • Post Points: 5
  • Fri, Nov 4 2011 12:29 AM

    • Shahnaf
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    • Posts 14
    • Points 265
    Re: OpAmp Simulation in Cadence Spectre Reply

     Hi Andrew,

    I have attached the snapshots of the "Solutions" library which is the default library from Cadence.
    I am using Cadence version 6.1.5.

    I found op_amp schematic in Solutions library with differential amplifier and CS amplifier as blocks.
    Then I got to see the schematic of the differential amplifier and CS amplifier in the "Solutions" folder.

    I have attached the circuit I have used. My intention is to use OpAmp as linear multiplier for ASK modulation. But I had never used Opamp in my design. Moreover, I had never used any symbols from "Solutions" library. In order to test whether the symbol suits to my application, I had simulated a simple voltage amplifier circuit which amplifies the input signal by 10 times.

    The last two are the sample circuit I simulated and the plot I got. But the expected plot is 10 times the input signal.

    Hope you understand my point now.

    Please let me know where I was wrong and how to correct the same.

    Thanks,
    Shahnaz.

    • Post Points: 20
  • Fri, Nov 4 2011 1:34 AM

    Re: OpAmp Simulation in Cadence Spectre Reply

    Shahnaz,

    That library is not (as far as I know) anything from Cadence. Go to the Library Manager, and over the name of the "Solutions" library in the Library column, do Right Mouse->Properties. In the resulting popup, you should see a readPath. Can you post that?

    You also didn't mention which "Cadence simulation manual" you were referring to earlier.

    In your last post you say you've attached the circuit you have used, but there's no attachment.

    Regards,

    Andrew. 

    • Post Points: 20
  • Fri, Nov 4 2011 2:21 AM

    • Shahnaf
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    • Joined on Mon, Aug 29 2011
    • Posts 14
    • Points 265
    Re: OpAmp Simulation in Cadence Spectre Reply

     Hi Andrew,

     

    I am unable to upload attachments from here.

    I will mail you. 

     

    Thanks!

    • Post Points: 20
  • Fri, Nov 4 2011 2:26 AM

    Re: OpAmp Simulation in Cadence Spectre Reply

    Really? Can't you go to the Options tab when posting, and specify the attachment there?

    Emailing me doesn't help others to help out - if this library is nothing to do with us, somebody else might recognize it.

    Also, to give the path, you should be able  to cut and paste the text from the form, rather than showing a screenshot.

    Andrew.

    • Post Points: 20
  • Fri, Nov 4 2011 2:40 AM

    • Shahnaf
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    • Joined on Mon, Aug 29 2011
    • Posts 14
    • Points 265
    Re: OpAmp Simulation in Cadence Spectre Reply

     Andrew,

    Through the options tab, I am able to do only one attachment but not multiple :-(

    When I tried to add second one, the first one gets removed automatically.

    I tried that option.

    Below is the path:

    /Application/cadence/Cadence_db/cadence_ms_labs_613/cds.lib

    I opened the cds.lib file and found that the Solutions library is defined in it.

    I have attached the snapshot of the same. When I try to upload attachments through cadence online forum, I am unable to attach them. So, I am sending mail to you.

     

    Regarding the manual, its not a cadence manual. Its the manual done by University of Mexico.

     

    I have attached the snapshots of the "Solutions" library which is the default library from Cadence.
    I am using Cadence version 6.1.5.

    I found op_amp schematic in Solutions library with differential amplifier and CS amplifier as blocks.

    Then I got to see the schematic of the differential amplifier and CS amplifier in the "Solutions" folder.

     

    My intention is to use OpAmp as linear multiplier for ASK modulation. But I had never used Opamp in my design. Moreover, I had never used any symbols from "Solutions" library. In order to test whether the symbol suits to my application, I had simulated a simple voltage amplifier circuit which amplifies the input signal by 10 times.


    Hope you understand my point now.

    Please let me know where I was wrong and how to correct the same.

     

    Thanks,

    Shahnaz

     


     

    • Post Points: 20
  • Fri, Nov 4 2011 2:54 AM

    Re: OpAmp Simulation in Cadence Spectre Reply

    Well, you didn't answer my question about the path to the Solutions library, but the cds.lib is not a "default" cds.lib but one that you have in that particular directory, and is not something provided by Cadence. Similarly any manual provided by the University of Mexico is unlikely to be something that I would be familiar with. Maybe this Solutions library was provide by the University of Mexico too?

    Since the Solutions library nor the manual you are referring to are anything I have ever seen before, nor something I have access to, I'm afraid there is nothing I can do to help. I would suggest that you contact the University of Mexico since the manual (and quite possibly the library) is from them.

    I'm slightly mystified as to how you thought anyone could help you with data which we can't see, especially if you knew that the manual you were referring to was from a University.

    Also shows the benefit of providing sufficient information at the beginning. A lot of time has been wasted here trying to track down what your actual issue is. Remember this is a community forum, and is answered by people in their own time (including me - it is not part of my job at Cadence to respond on this forum).

    Regards,

    Andrew.

    • Post Points: 20
  • Fri, Nov 4 2011 3:30 AM

    • Shahnaf
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    • Joined on Mon, Aug 29 2011
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    • Points 265
    Re: OpAmp Simulation in Cadence Spectre Reply

     Andrew,

     

    I am not from University of Mexico. While googling, I found the Opamp symbol and tried to do some analogy between the two as the symbol looks same. Nothing is related to me and cadence manual designed by Mexico University. The biggest mistake from my end was to tell that its a cadence manual. After your reply, again i searched in google to find the same. Moreover, I was not allowed to attach more files. I am not sure of the reason.

    When I do right click on the Solutions library of main Library, the high lighted part is going off and so I checked the library path which I have sent you in my ealier mail.

    I am unable to upload more attachments to show my problem. 

    Since Solutions library is the default one and not created by us, I have posted this in the forum, so that I can get anykind of help. Since, you may understand the problem as you had been responding, I have asked you to reply through mail atleast so that I can send you the attachments.

     Anyway, I too have wasted my time by replying and responding.

    A big SORRY!! Thanks a lot.

    • Post Points: 20
  • Fri, Nov 4 2011 4:56 AM

    Re: OpAmp Simulation in Cadence Spectre Reply

    Shahnaf,

    I'm not sure what you mean by the "high lighted part is going off" - if you just mean that you can't see the entire path, you should be able to select the whole thing to paste here. 

    Alternatively, type this in the CIW:

    ddGetObj("Solutions")~>readPath

    and it will tell you where the library is located. Hopefully that might give you a clue as to who provided it.

    As you can imagine, I get a very large number of direct emails, and I cannot in general cope with supporting direct requests from customers all over the world, as well as those I cover as part of my job. I prefer discussions to be done on the forum, as then you are not dependent on just me - others can reply. You can attach one attachment to each post - I've no idea why you can't attach a file (maybe a zip file containing multiple pictures, if needed) - I think that's allowed. So that's why I have not followed up via email. 

    Regards,

    Andrew.

    • Post Points: 20
  • Fri, Nov 4 2011 11:04 AM

    • Shahnaf
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    Re: OpAmp Simulation in Cadence Spectre Reply
    Ya....Andrew, I understand your situation. I found op_amp schematic in Solutions library with differential amplifier and CS amplifier as blocks. Then I got to see the schematic of the differential amplifier and CS amplifier in the "Solutions" folder. Screenshot.png and screenshot-6.png shows the Solutions library. Screenshot-1,2,3,4 are the block diagram of the OpAmp and its internal schematic. Screenshot-5 is the OpAmp which I simulated Snapshot.png is the plot I got. I have attached the circuit I have used. My intention is to use OpAmp as linear multiplier for ASK modulation. But I had never used Opamp in my design. Moreover, I had never used any symbols from "Solutions" library. In order to test whether the symbol suits to my application, I had simulated a simple voltage amplifier circuit which amplifies the input signal by 10 times. The last two are the sample circuit I simulated and the plot I got. But the expected plot is 10 times the input signal. I am out of office and so couldn't check the path. Just see whether you can provide any hint based on the attached files. Thanks in advance.
    • Post Points: 20
  • Fri, Nov 4 2011 11:41 AM

    Re: OpAmp Simulation in Cadence Spectre Reply

    Looking at your picture (Screenshot-5.png), you have a sine wave input with 5 volts amplitude. With a gain of 10, you'd have 50V output amplitude, but you only have +/-15V supplies, so clearly it wouldn't be able to generate signals that big. That's one mistake, at least (although don't think it's the only one).

    The Solutions library appears to be in the cadence_ms_labs_613 directory - you probably should try to find out where that came from. Is +/- 15V even suitable supply voltages? That's not exactly typical for modern processes...

    Going into the detail of why this circuit (for which I can't see any more than just some screenshots) is not really something I have time to do; maybe somebody else can spare the time - but the right things to  do are probably either to read a book on analog circuit design, or to contact whoever provided this "lab" database and find out how it is intended to be used, or to look at other configurations in the same library and try similar situations. It's an artificial example anyway, so it's not going to help you unless it's realised for a specific process which is the same as the process you're planning to use.

    Regards,

    Andrew.

    • Post Points: 5
  • Fri, Dec 6 2013 12:48 AM

    • kanth447
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    Re: OpAmp Simulation in Cadence Spectre Reply

    I want to do differential amplifier design and simulation results of  differential ampifier in 180nm technology using cadence virtuoso .So, please help me to simulate on AC analysis.

     

    • Post Points: 20
  • Fri, Dec 6 2013 1:54 AM

    Re: OpAmp Simulation in Cadence Spectre Reply

    Please read the forum guidelines. You didn't really ask a question, at least not a precise question. Also, you posted on the end of a 2 year old thread, which the guidelines ask you not to do.

    Andrew.

    • Post Points: 20
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Started by Shahnaf at 03 Nov 2011 08:49 AM. Topic has 19 replies.