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31 Threads found on Open Loop Test
Put it inside the classic op amp measurement loop, let it chatter and look for 50% duty (via the integrator threshold). That's how we did it and I believe how it still gets done, on production ATE. open loop DC or triangle wave stimulus can get you close but not any decent accuracy / repeatability.
Stability is usually analyzed with unity gain step response or open loop gain-phase or closed loop gain-phase. Which case did you have in mind?
Hi I'm trying to measure the open loop gain of an opamp in the lab. I'm trying to implement the first circuit in from the pdf below Just want to input on how this circuit works. Is it currently configured to work on a single supply opamp, or do I need to change
A simulation setup does not necessary need load resistors, but it would usually refer to the load conditions intended for the operation of your amplifier. That's a point you need to answer, we can't know. Besides suitable load impedances, a simulation setup has to provide a means to bias the amplifier for open loop gain measurement, that's the same
Check this site: It gives a thorough review how to test open loop gain gain without opening the loop.
To avoid pulling I select offset PLL structure. But at fractional frequency the on-chip PA deteriorates PLL IPN so much, larger power out worse IPN. At integer frequency it's OK. In open loop test the VCO performance doesn't change. If does PA affect N-divider, PFD or CP's linearity? What's the path and mechanism? Thank you.
hello, i need two stage opamp schematic and test bench for open loop gain>70db iam not open loop gain >than 70db i have implemented the opamp in BIQUAD GIC NOTCH FILTER . please help ........
Whatever it is that you are trying to test, I would first simulate it first. If you want to make it simple, start with simulating the system in the open-loop configuration (without a feedback controller). To do this, apply a gating signal to the switching device by using a pulse source with appropriate duty ratio and frequency. You can use (...)
LAW, is it wise to measure the open-loop gain for a device that has a 10kohms output resistance? Such a device can be classified (nearly) as an OTA. Do you intend to measure without any (nominal) load?
Hi,there I have designed a 2-stage amp and used as voltage buffer,the vdd is 1.5v and vss is 0v.I want to test its open-loop gain,so I use the circuit as fig1(open-loop).The input is an diff.pairs,and the Vcm is set to 0.7v,their acm is set to 1v and dc voltage is set to 0v.Then I run AC analysis and sweep (...)
you can run a loop back test to check whether cable is working or not.. open hyper terminal if you done have one you can download for windows7 and configure it.. short pin 2 and pin3 of the rs232 cable output and type a char if its echoes back then cable is ok
I would suggest you look into cmos analog design book by phillip allen ( 2nd edition). it has a chapter which discusses how to design two stage amplifier and the trade offs. do not test your amplifier in open loop, have a closed loop system which a big resistor(1GOhms) between ur output and negative input. this will (...)
Greeting, I would like to test the following specification of Opamp: loop Characterization: 1.1 Differential gain (using .AC) 1.2 Phase Margin 1.3 Output Swing 1.4 Unity Gain Bandwidth 1.5 Current Consumption 1.6 Input offset 2. Close loop Characterization 2.1 THD (using .FFT) (...)
The null opamp test circuit can do the job to find open loop gain of the opamp. And the pdf link above was fail. You can goto read some book to find the way to use this great circuit. Give you some hint, Av=Vo/Vi
about the OPamp psrr measurement , should we test it in 1 openloop like connect the two input , then measure the output variation or 2 close loop : like connect the op as the Opamp buffer then measure the output variation? the two kind of testing have very different result. which one is (...)
I don't think so because these parasitic values are also effective during open loop simulations - if these simulations are performed correctly!!!. It would be best to show the circuit under test as well as the open-loop simulation arrangement.
Theoretically for a single loop you can open it at any node, analyze the phase margin and should get the same results of stability
When measuring the output voltage swing of an opamp, we should use a closed loop configuration. Measuring the opamp swing in open loop configuration does not make sense. Is that right? What is the best closed loop configuration to test the output voltage swing especially a fully differential opamp?
Hi, I want to test the ac analysis of opamp with Bipolar input stages. I used the big R and big C in the feedback loop to open the feedback for AC analysis.This works only for the CMOS input stages. But bipolar input stages need base currents.. Can anyone help me with the test circuit? Thank you..
i have designed a folded cascode fully differential opamp used for pipelined adc(1.5 bit per stage),but there are some problems: when i test it in open loop with ideal cmfb(vcvs source),the GBW is 103M,dc gain is 80 db,-3db bandwidth is about 10khz;however,when i test it in closed loop with sc-cmfb,there (...)