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https://designers-guide.org/forum/YaBB.pl Design >> Analog Design >> Bandwidth, Unity Gain Bandwith, OTA Bandwidth, DC-DC Converter Feedback https://designers-guide.org/forum/YaBB.pl?num=1410960989 Message started by AMSA on Sep 17th, 2014, 6:36am |
Title: Bandwidth, Unity Gain Bandwith, OTA Bandwidth, DC-DC Converter Feedback Post by AMSA on Sep 17th, 2014, 6:36am Hi guys, I am designing a OTA amplifier to work as an error amplifier/compensator in a dc-dc converter. As a first approach, to determine the gm of the input differential pair, I want to use the GBW. Because I am switching at very high frequency (>100MHz) I don't know which value of GBW the OTA must have in order to perform correctly when I close the feedback loop with him there. I'd like to hear from you what is your opinion on this. In which way the GBW (unity gain bandwidth product) influences the compensator performance and the feedback loop. Because I have to select the desired crossover frequency, say, 60MHz, of the closed loop system, the OTA needs a GBW of 100MHz? 120MHz? Thanks in advance. Kind regards. |
Title: Re: Bandwidth, Unity Gain Bandwith, OTA Bandwidth, DC-DC Converter Feedback Post by AnilReddy on Sep 18th, 2014, 5:43am Hi AMSA, It doesn't seem like you are using inductor here, because the switching frequency is very high.. Is it a switched cap dc-dc converter? Bye |
Title: Re: Bandwidth, Unity Gain Bandwith, OTA Bandwidth, DC-DC Converter Feedback Post by AnilReddy on Sep 18th, 2014, 6:08am Hi, I just read your other post (http://www.designers-guide.org/Forum/YaBB.pl?num=1410447504) and it seems similar to this one. The main requirements for error amplifier in dc-dc converter are 1. it's gain need to be high. High enough to overcome the attenuation coming from power stage. High enough to reduce steady state error. 2. it's input offset should be small enough not create any error when referred to the output. 3. it's output voltage swing is as large as possible to accomadate the range of duty cycles you are trying to achieve. 4. it's gm should be as high as possible so that during transient load steps output recovers faster. 5. it's slewing behavior should be good for the same reasoning above. 6. it's power consuption should be low to improve efficiency. 7. it's UGB should be as high as possible so that the compensation zeros you put stay at approximately same location as that of hand calculation. Bye |
Title: Re: Bandwidth, Unity Gain Bandwith, OTA Bandwidth, DC-DC Converter Feedback Post by AMSA on Sep 22nd, 2014, 2:04am Anyone? |
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