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firsttimedesigning
Joined: 04 Jul 2007
Posts: 96
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 29 Jan 2008 11:52 Measuring an Op-Amp |
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| I would like to measure the characteristics of an Op-Amp such as the DC gain, AC gain, bandwidth, 3 dB frequency... The problem is that if I connect the resistors from outside of the op-amp, there will be parasitic capacitance that could affect the performance of the op-amp significantly. So...how to measure? any idea?
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FvM
Joined: 22 Jan 2008
Posts: 1825
Helped: 332
Location: Bochum, Germany
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| 29 Jan 2008 12:25 Re: Measuring an Op-Amp |
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Hello,
there are more issues you didn't mention. The DUT has to be biased, the probe loads the circuit, generator is non-ideal, network-analyzer or whatever you use has limited resolution, etc. This is common to instrumentation technique.
Analog design literature and manufacturer applications should give some ideas of appropriate test circuits. I prefer to think myself, when a problem is formulated. You also should be able to find an optimal test circuit for each parameter.
Regards,
Frank
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firsttimedesigning
Joined: 04 Jul 2007
Posts: 96
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| 30 Jan 2008 10:54 Re: Measuring an Op-Amp |
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Thank you for replying. But the problem is i have absolutely no idea how to find the optimal circuit for testing the parameter. can you maybe give me an example?
hopefully i can learn from that example and start from there...
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hdmi
Joined: 02 Feb 2008
Posts: 17
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| 02 Feb 2008 2:56 Re: Measuring an Op-Amp |
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I believe you can go to most analog houses and search for the application notes, TI, National Semi, Maxim, Linear Tech etc.,
One example, go to Analog Device website and search for AppNote AN-356 (Op measurement) and AN-253 (noise measurement).
Added after 1 minutes:
I believe you can go to most analog houses and search for the application notes, TI, National Semi, Maxim, Linear Tech etc.,
One example, go to Analog Device website and search for AppNote AN-356 (Op measurement) and AN-253 (noise measurement).
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maninnet
Joined: 25 Oct 2007
Posts: 106
Helped: 2
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| 05 Feb 2008 23:20 Measuring an Op-Amp |
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| try " opamp for every one" from ti site
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rokibulalam
Joined: 07 Jan 2008
Posts: 11
Location: Bangladesh
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| 11 Feb 2008 9:14 Re: Measuring an Op-Amp |
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| firsttimedesigning wrote: |
| I would like to measure the characteristics of an Op-Amp such as the DC gain, AC gain, bandwidth, 3 dB frequency... The problem is that if I connect the resistors from outside of the op-amp, there will be parasitic capacitance that could affect the performance of the op-amp significantly. So...how to measure? any idea? |
Yes it is sure that parasitic capacitance occurs. But if the input signal is not of very high frequecy then I think there will not be any difference.
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remotest
Joined: 12 Feb 2008
Posts: 12
Helped: 2
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| 18 Feb 2008 6:41 Re: Measuring an Op-Amp |
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| for this quary u should refer cmos analog circuit design by allen and holberg.
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armixic
Joined: 09 Mar 2006
Posts: 30
Helped: 2
Location: U.S.A
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| 16 Mar 2008 9:16 Re: Measuring an Op-Amp |
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| operation frequency is the key , when work at low frequency, Cpar won't hurt much
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paley
Joined: 03 Mar 2006
Posts: 88
Helped: 3
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| 21 Mar 2008 11:14 Measuring an Op-Amp |
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| you can use a same mos connect to the another side of res
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luojiexiaojun
Joined: 14 Mar 2008
Posts: 21
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| 21 Mar 2008 16:43 Measuring an Op-Amp |
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| in analog circuit design by allen and holberg,you can get much help
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lxandlj
Joined: 30 Mar 2008
Posts: 7
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| 16 Apr 2008 16:13 Re: Measuring an Op-Amp |
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you think too much .
certainly , what's you say is right .
but , in pratice , some factors can be ingored , which need some experience .
you only in theory , the practice show more sunshine.
for example , parasitic capacitance ,this only in very high frenquency works
when in high frenquency , other parasitic factors must consider too.
it's very complex.
refer to the signal integrality(SI).
good luck .
regards nemo
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yezeg
Joined: 12 Jan 2006
Posts: 15
Helped: 1
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| 26 Apr 2008 14:59 Measuring an Op-Amp |
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Johan H.Huijsing's book Operational Amplifiers Theory and Desin
CH2 2.6 dissguss the OPA's measurement
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northeast1
Joined: 21 Jun 2007
Posts: 145
Helped: 4
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| 28 Apr 2008 5:08 Re: Measuring an Op-Amp |
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| firsttimedesigning wrote: |
| I would like to measure the characteristics of an Op-Amp such as the DC gain, AC gain, bandwidth, 3 dB frequency... The problem is that if I connect the resistors from outside of the op-amp, there will be parasitic capacitance that could affect the performance of the op-amp significantly. So...how to measure? any idea? |
simulation or reality?
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apmrao
Joined: 02 Aug 2006
Posts: 9
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| 29 Apr 2008 9:22 Measuring an Op-Amp |
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| what band of interested frequency?
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melc
Joined: 08 Apr 2005
Posts: 386
Helped: 44
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| 01 May 2008 21:37 Re: Measuring an Op-Amp |
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| apmrao wrote: |
| what band of interested frequency? |
Let say just for talking (because the initiator of this post could be already died) that it's about 800MHz at -3dB.
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naveen223
Joined: 05 May 2008
Posts: 8
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| 05 May 2008 15:58 Measuring an Op-Amp |
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| I am doing project which needs opamps. I need to run them on 5V . please suggest some ics
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ckshivaram
Joined: 21 Apr 2008
Posts: 283
Helped: 19
Location: korea
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| 08 May 2008 7:57 Measuring an Op-Amp |
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| try to use TL084 this will reduce the noise and any stray effect and any other offset that are visible in LM324, OP07, or any other opamp
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northeast1
Joined: 21 Jun 2007
Posts: 145
Helped: 4
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| 09 May 2008 4:02 Re: Measuring an Op-Amp |
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| firsttimedesigning wrote: |
| I would like to measure the characteristics of an Op-Amp such as the DC gain, AC gain, bandwidth, 3 dB frequency... The problem is that if I connect the resistors from outside of the op-amp, there will be parasitic capacitance that could affect the performance of the op-amp significantly. So...how to measure? any idea? |
If the circuit you care is about 20MHz, you can ignore the problem
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