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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> measuring op amp specs https://designers-guide.org/forum/YaBB.pl?num=1320004411 Message started by mixed_signal on Oct 30th, 2011, 12:53pm |
Title: measuring op amp specs Post by mixed_signal on Oct 30th, 2011, 12:53pm Hi, I have designed a single input single output amplifier for low power applications. It has dynamic biasing and has two phases: biasing phase and amplifying phase and has clocks. I want to measure the slew rate, settling time, input reffered noise, input comon mode range, output common range, offset. How can i measure them systematically. For slew rate measurement, i know that opamp is configured as voltage follower and then step input is given. What should i do in case single input single output case? Should i use any feedback? |
Title: Re: measuring op amp specs Post by raja.cedt on Oct 31st, 2011, 1:26pm What do you mean by dynamic biasing, is bias current chages over the operation? Any how to for all measurements use feedback at least dc -ve fb and may be for ac openloop is ifne. Thanks, raj. |
Title: Re: measuring op amp specs Post by mixed_signal on Nov 1st, 2011, 7:06pm Yes the bias current changes and more important is that the amplifier has a biasing phase where it is switched to biasing circuitry and gets biased. During amplifying phase input is applied and biasing circuit is cut off. There are capacitors to keep it biased. |
Title: Re: measuring op amp specs Post by weber8722 on Nov 17th, 2011, 8:03am BTW, measuring SR as follower is not always sooo good. Image your output is rail-to-rail, but input not. So you will overdrive the input, if this is not the case in your real application you may get inconsistant results. Better always do both standard tests and test very close to the actual application (maybe a 100X-amp, not a unity-gain-buffer). |
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