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14 Threads found on Current Source Psrr
Hi, I am working in a 28nm process with 1V supply where I need gain and bandwidth. It's not really possible to use cascodes and not fun at all to even use a diff pair because gmro is effectively halfed: first lower VDS due to tail current source and second gain is gm*(ron//rop). Now if I look at this years ISSCC so many designs use just inver
I would like to fill some holes in my op-amp knowledge. I currently have some static noise and slight humming in my recent amplifier design and I'm thinking that the source might be the psrr of the op-amp used, but how do I calculate it? I made this simple circuit that has +/-25V rails with 1V of humming present: 117537
current source on bottom is essential to psrr
hello, i am designing a v to i converter, voltage input range is 0-5v dc, n the output current should range from 0-100ma. Please help me with this. please upload the necessary circuits. which opamp is best suitable for this application.
For manual calculation, it can be done similar to small-signal AC analysis. The difference is the input AC voltage is added to supply. The output is the current output.
With tail current source, the current consumption is limited and known, so the voltage swing is controlled as well. The psrr is high. Without the tail source, the phase noise would be the best. As a compromise a tail resistor is used in many designs.
Please tell me ,thank you Higher impedance means that the current will not change obviously with Supply. So the psrr is better.
i have designed a ptat current source,the Vref=1.239V,TC=10ppm(tt)\38ppm(ff) the change of Vref is 3mV(tt)\7mV(ff) when VDD is 1.62-1.98V; is that ok? how's a good ptat current source?what's the Tc and change rate of Vref with VDD, besides,how to improve the psrr and TC simultaneously?what's the effect (...)
XF is very usefull for CMRR and psrr characterization. Output impedance u are able to easy obtain using AC analysis. Just put AC voltage source (e.g. 1V) with 0V DC in series with output of amplifier. Measure AC voltage at ouput and Ac current flow though output: Zout=Vout/Iout P.S. Generally when you simulate OpAMP u should use (...)
Hi It sets similar VDS for current mirror. please sketch circuit of current source. regards
Hi, It depends. If you use transient simulation (for calculating psrr, which is the proper) for a relatively long time, It MIGHT tell you if the LDO is stable or not. If you use AC simulation, then the answer is NO. The best way to make sure if the LDO is stable is to put a pulse- wave current source in the output of the LDO ( The (...)
John Xu, I agree with you. I think it is a decoupling cap to increase the psrr. it's value depend on current flow on the middle leg of figure!, noise attenuation and frequency which we want to eliminate (eg. 50Hz). Regards, Davood Amerion
connect cap from vdd to gnd or connect cap from current source transistors to vdd or gnd the above way can inrove psrr, thanks
Basically what you want to understand is the effect that the variations in the common mode voltage and the supply voltage have on the differential output current. This can be done using a AC analysis were your AC supply is either connected in series with the supply voltage source or in series with the common-mode voltage source. This (...)