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How to measure the characteristics of an Op-Amp ?

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firsttimedesigning

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Measuring an Op-Amp

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?
 

Re: Measuring an Op-Amp

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
 

Re: Measuring an Op-Amp

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...
 

Re: Measuring an Op-Amp

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).
 

Measuring an Op-Amp

try " opamp for every one" from ti site
 

Re: Measuring an Op-Amp

firsttimedesigning said:
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?
Click to expand...


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.
 

Re: Measuring an Op-Amp

for this quary u should refer cmos analog circuit design by allen and holberg.
 

Re: Measuring an Op-Amp

operation frequency is the key , when work at low frequency, Cpar won't hurt much
 

Measuring an Op-Amp

you can use a same mos connect to the another side of res
 

Measuring an Op-Amp

in analog circuit design by allen and holberg,you can get much help
 

Re: Measuring an Op-Amp

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
 

Measuring an Op-Amp

Johan H.Huijsing's book Operational Amplifiers Theory and Desin
CH2 2.6 dissguss the OPA's measurement
 

Re: Measuring an Op-Amp

firsttimedesigning said:
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?
Click to expand...

simulation or reality?
 

Measuring an Op-Amp

what band of interested frequency?
 

Re: Measuring an Op-Amp

apmrao said:
what band of interested frequency?
Click to expand...

Let say just for talking (because the initiator of this post could be already died) that it's about 800MHz at -3dB.
 

Measuring an Op-Amp

I am doing project which needs opamps. I need to run them on 5V . please suggest some ics
 

Measuring an Op-Amp

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
 

Re: Measuring an Op-Amp

firsttimedesigning said:
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?
Click to expand...

If the circuit you care is about 20MHz, you can ignore the problem
 

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