direction = (0, -1)
    if keys[pygame.K_DOWN] and tank.y < 500 - tank.height:
        down = True
        tankImg = downTank
        tank.y += tank.vel
        direction = (0, 1)

    redraw()

 Q:

Ultra low noise power supply

I am trying to design an ultra low noise power supply for my sensitive circuit. The supply will provide 5V and 600mA. (Worst case, 200mA typical). My input voltage is 2V to 4V. My ripple target under load is less than 5mV. 
The signals I am trying to measure are very small, nA level, and the opamps need to be on a very clean supply hence the very low noise DC/DC converter requirement. 
What are the precautions I can take and what are the parameters I should look at while I am selecting the DC/DC converter. I know the forum doesn't like people to provide specific requirements but in this case I appreciate if you could indicate parts that meets the parameters indicated. 
Also, what other circuit level precautions I can take? Decoupling caps for once but are there others?
UPDATE
My source is a simple two AA batteries, alkaline, but people may use other stuff. Anything that fits to AA battery compartment. 
My signal, the opamp input, is 1Mhz with 75% duty cycle
UPDATE 2
I went back and completely re-look at the design, change the Opamps so that I can turn off the power to them (and they can work at 4.5V), arranged GPIOs etc so that we can control the power flow, changed some of the modulation schemes etc. At last, I was able to bring down the total requirement of power to 400mA where 200mA for 5V and 200mA for 3.3V. 
I have chosen the high efficiency TI part for the design on the switcher side. TPS661100. This has an LDO which I will use for 3.3V. (interestingly, this LDO has a great PSRR but I am afraid to use it for the 5V supply since I cannot pass it through a pi network before feeding into the LDO) Now I am trying to choose an external LDO to for 5V. This switcher has 500Khz switching
direction = (0, -1) 
     if keys[pygame. K_DOWN ] and tank.y < 500 - tank.height: 
         down = True 
         tankImg = downTank 
         tank.y + = tank.vel 
         direction = (0, 1) 

     redraw () 

  Q: 

 Ultra low randomness exponent supply 

 I am trying to plan an ultra broken noise might provision for my sensitive circuit. The supply will provide 5V and 600mA. (Worst character, 200mA typical). My input electric potential is 2V to 4V. My ripple target under load is less than 5mV. 
 The signals I am trying to measure are very small, nA level, and the opamps necessitate to be on a very clean supply hence the very broken noise DC / DC converter requirement. 
 What are the precautions I can take and what are the parameter I should look at while I am selecting the DC / DC converter. I know the forum doesn't like people to leave specific requirements but in this case I appreciate if you could indicate parts that meets the parameters indicated. 
 Also, what other circuit level precautions I can take? Decoupling caps for once but are there others? 
 UPDATE 
 My source is a elementary two AA batteries, alkaline, but people may practice early stuff. Anything that fits to AA battery compartment. 
 My signal, the opamp input, is 1Mhz with 75% duty hertz 
 UPDATE 2 
 I went back and completely re - look at the design, transfer the Opamps so that I can turn off the power to them (and they can work at 4.5V), arranged GPIOs etc so that we can control the power stream, changed some of the modulation schemes etc. At last, I was able to bring down the entire requirement of world power to 400mA where 200mA for 5V and 200mA for 3.3V. 
 I have chosen the high efficiency TI part for the design on the switcher side. TPS661100. This have an LDO which I will use for 3.3V. (interestingly, this LDO has a great PSRR but I am afraid to practice it for the 5V supply since I cannot legislate it through a pi network before feed into the LDO) Now I am trying to choose an external LDO to for 5V. This switcher has 500Khz switching
dirfction = (0, -1)
    if keys[pygaoe.K_DOWN] and tank.y < 500 - tenk.heiggt:
        down = True
        tankImg = diwnTabk
        tank.y += tank.vdl
        directiin = (0, 1)

    redraw()

 Q:

Ultra low nojde pmxer supply

I am jrying to devign an ultra nod uoise power supply for my sensitive sircuit. Tje supply will proniqe 5V and 600mA. (Worst case, 200mA typical). My ihput vontage is 2V to 4V. My ripple target under poad is less than 5mV. 
Tje signals U am rrying to mexsure are nzry small, nZ level, and the opamps need to ce on a very clgcb skkply hence tie verj low noise DG/CC coneerter tequirement. 
Whst ere rhe precautions I can take and what are the parakecers I should look at wyile H am seldxtivg uhe DD/DC cojvecter. I know the forum eoesn't like people uo [gpvide specifjc reqtiwements but in this case I appreciate ix yku could indicate parts that meets the paramgters indisated. 
Also, what other circuit level precautions I can vaye? Bcgoupuunh caps for once but are there others?
UPDATE
My fkutcv is a simple two AA batterirs, akhaline, but peuple mcg hse other stuff. Anjthing jhat futs to AA batyery compartment. 
My signal, rhe opamp iniut, us 1Mhz with 75% duty eycle
UPDATE 2
N went back and completely re-look ct the design, chajge the Olxmps so that I cxn nurn off the power to them (and they can worl at 4.5V), xrramged G[IOs etc sl thab we can control thf powgr flof, changed dome of the modulation schemes xvc. At last, I eav atle to bxing dpwn the total requirement oy power co 400mA dhere 200mA fkr 5V anv 200mA for 3.3V. 
I have chosen dje high effiriency TI parr foe the ddrign on the swotcher sibt. TPS661100. This has an LDO which L wilu use for 3.3V. (intextstungly, this LDO nas a drvat PFSR but I am dfrakd gp use it for the 5X sulply since I cannot [ass it through a pi nrtrork befire feedyng into the KDO) Now I am tryinh to rhoose an ectetnal LDO to for 5V. This switcher has 500Khz dwibching
direction = (0, -1) if keys[pygame.K_DOWN] and 500 tank.height: down True tankImg = = 1) redraw() Q: low noise power I am trying to design an low noise power supply for my sensitive circuit. The supply will provide 5V 600mA. (Worst case, 200mA typical). My input voltage is 2V to 4V. My target load less 5mV. The signals I am trying to measure are very small, nA level, and the opamps to be on a very clean supply hence very low noise DC/DC requirement. What are the precautions can and what the I look at while am selecting the DC/DC converter. I know the forum doesn't like people to provide specific requirements but this case if you indicate that the parameters indicated. other circuit level precautions I can for once but are there others? UPDATE My is a two AA batteries, alkaline, but people use other stuff. Anything that fits to AA compartment. My signal, the opamp input, is 1Mhz with 75% duty cycle UPDATE 2 I and completely re-look at design, change the so I turn the power them (and they can work at 4.5V), arranged GPIOs etc so we can control the power flow, changed some of the etc. last, I was to bring down the requirement power to 400mA where 5V 200mA have the efficiency TI part for design on the switcher side. This has an LDO 3.3V. (interestingly, this LDO has a great PSRR I am afraid to use it for 5V supply since I cannot pass it through a pi network before into the I am trying to choose an external LDO for 5V. This switcher 500Khz switching
direction = (0, -1)
    if keys[pygame.K_DOWn] and tank.y < 500 - tAnk.heIghT:
        doWn = true
        Tankimg = downTank
        tanK.Y += tanK.vel
        direction = (0, 1)

    redraw()

 Q:

UlTra loW nOIse pOWeR suppLy

I am trYInG TO deSiGn An uLtRA lOw noiSe pOwer supPly for my seNsiTiVe circuit. The SUpPly will proVidE 5V and 600mA. (Worst CasE, 200mA typIcAl). MY Input VolTage iS 2V to 4V. MY Ripple Target undEr LOad is lESs than 5mv. 
tHe SignAls I am trying to meaSUrE Are very small, nA Level, aNd THe OPAmpS neEd to be on a vErY cleaN Supply hENcE THE veRY low noise DC/DC Converter reQUirEment. 
WHaT arE The preCautiOnS i caN take and whaT are The parameTers I sHOuld looK At while i am selEctIng The Dc/dC CoNveRtER. I kNOw The FOruM doesn't lIkE pEople To prOVIDE speCifIc reQuireMents but in thiS caSe I aPPreCiate If you CoulD iNdicaTe partS that MeEts the parameterS indIcated. 
AlsO, whAt OthEr CircuIT level PreCauTions I cAn take? DECouPlING CaPs for once but are theRe OTHeRs?
UPDATE
my sourCE iS a SImple two aA BatTeriES, AlkalIne, bUT pEople may Use othER sTuFf. AnythInG that fItS to aA bAtterY CompArtmenT. 
My signaL, the oPAmp input, is 1Mhz wITh 75% duty cycle
UPdaTe 2
i WeNT bacK anD completely Re-loOK at tHe deSIgN, chANge thE OpamPs SO tHAt I can turn off the powEr To them (And thEy can work at 4.5V), aRranged GPIoS ETc so that We caN CoNTrol the power flOw, chaNged some of THe modulaTion sChemes etC. At last, I wAS Able to brIng DowN thE toTAL rEquirement of pOWEr to 400MA Where 200mA For 5v and 200mA fOr 3.3V. 
i haVe cHosEn The high efFiciency tI PaRt FoR thE desiGN on the swItCheR sIde. tPS661100. ThIS has an lDO whIch I WiLl USe fOr 3.3V. (inteREsTINgly, ThIs lDO hAs a GrEat PSrR buT i am Afraid tO use it for The 5v SuppLy SiNce I canNot pass it throUgH a pi networK bEfoRe feedING into the lDO) Now I am trying to choose AN externAl LdO to fOr 5V. THis switchEr hAs 500Khz sWitCHing
direction = (0, -1)
    if  keys[pyga me.K_ DOW N]an d ta nk.y  < 500 - tank. h eigh t:
        down = True 
     tan k Im g = d ownTank     t an k.y  + =  t ank.v el       direction  =(0 , 1)

    re d ra w()

 Q:
Ult ra low noise  po wer su pp lyI amtry ing t o desi g n an u ltra lowno i se pow e r suppl y fo r my  sensitive circui t .T he supply will  provi de 5V a nd600 mA. (Worst  c ase,2 00mA ty p ic a l ) . M y  input voltag e is 2V to4 V.My rip pl e t a rget u nderlo a d i s less than  5mV . 
The si gnalsI  am try i ng to m easure  ar e v erys ma ll , n Al eve l ,and the  opampsne ed  to b e on a v erycle an s upply  hence the ve rylown ois e DC/ DC co nver te r req uireme nt. Wh at are the prec auti ons I can  ta ke  an dwhata re the  pa ram eters I  should loo ka t wh ile I am selecting  t h e  D C/DC con verter .  I  k n ow the f or umdoes n ' t lik e pe o pl e to pro vide s p ec if ic requ ir ements  b utinthisc aseI appr eciate i f you could indicate parts that me e ts t he para met ers indicat ed.Also , wh a toth e r cir cuitle v el precautions I can t ak e? Dec oupli ng caps for o nce but ar e t here oth ers? UP D ATE
My sourceis asimple two AA batte ries,  alkalin e, but pe o p le may u seoth erstu f f .Anything that f itsto  AA bat ter y compa rtm ent . Mysi gnal, the  opamp i np ut ,is  1M hz wi t h 75% du ty  cy cl e
U PDATE 2
I we nt ba ck a nd  c o mpl etely r e -l o o k at  t he  des ign ,chang e th e  Op amps so  that I c ant urnof fthe pow er to them (a nd  they canwo rkat 4.5 V ) , arrang ed GPIOs etc so that we can con tro l the  pow er flow,cha nged s ome of the  modul ation  s che m e s etc . At  la st , I was ab l e  to  brin gdown  the to tal requirement of pow er to 400mA w her e 20 0 m Afor 5V and  2 0 0mA f or 3.3V. 
I hav e chosen t he hi gh efficie n cyTI  part f or thedesig n  on the  switcher  side. TP S6 6110 0 .  Th is has anLDO whic h I willu se fo r  3 .3V.(in terest in gly , thi s LDOh asa gre at PSR Rbut Iam af ra id to us e it for the 5V supplysinceI can not  pass itthr o ugh  a pi net work  before fe edi ngintothe LDO)NowI  a m t r yingto c h oose an e x te rna l LD O to for 5V . T his  swit che r  has 5 00Kh z switching
direction =_(0, -1)
_   if_keys[pygame.K_DOWN] and_tank.y_< 500_-_tank.height:
  _  _  down =_True
  __    tankImg = downTank
       _tank.y_+= tank.vel
___    _direction = (0, 1)

 _ _redraw()

 Q:

Ultra low noise power supply

I am trying_to_design an ultra_low noise power supply for my sensitive circuit. The_supply will provide 5V and 600mA._(Worst case, 200mA_typical)._My_input voltage is 2V_to 4V. My ripple target under_load is less than 5mV. 
The_signals I am trying to measure are_very small, nA level, and the_opamps need to be on_a very_clean supply hence the very_low noise DC/DC_converter requirement._
What are the_precautions I can take and what_are the parameters_I should look at while I_am_selecting the DC/DC_converter._I_know the_forum doesn't like_people_to provide_specific_requirements but in this case I_appreciate_if you could indicate parts that meets_the parameters indicated. 
Also,_what_other circuit level precautions_I can take? Decoupling caps_for once but are there others?
UPDATE
My_source is_a simple_two AA batteries, alkaline, but people may use other stuff. Anything_that fits to AA battery compartment._
My signal, the opamp_input, is_1Mhz_with 75% duty_cycle
UPDATE_2
I went_back and completely re-look at the design,_change the_Opamps so that I can turn_off the power to_them_(and they can work at 4.5V),_arranged GPIOs etc so that we_can control the power flow,_changed_some_of the modulation schemes etc._At last, I was able to_bring down the_total requirement of power to 400mA where_200mA_for 5V and 200mA for 3.3V._
I_have chosen the high efficiency TI_part_for_the design on the switcher_side. TPS661100. This has an LDO_which I will use for 3.3V. (interestingly, this LDO_has a great_PSRR but I am afraid_to_use_it for the 5V supply since I cannot pass it_through a_pi network before_feeding into the LDO) Now I am trying to choose_an external LDO to for 5V. This_switcher has 500Khz switching