c-multiplier, real life
in [Design]
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From: John Larkin on 4 Jun 2010 17:08 On Sat, 05 Jun 2010 06:46:26 +1000, Grant <omg(a)grrr.id.au> wrote: >On Fri, 04 Jun 2010 08:11:34 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Fri, 04 Jun 2010 09:10:03 GMT, Jan Panteltje >><pNaonStpealmtje(a)yahoo.com> wrote: >> >>>On a sunny day (Thu, 03 Jun 2010 18:37:42 -0400) it happened Jamie >>><jamie_ka1lpa_not_valid_after_ka1lpa_(a)charter.net> wrote in >>><S4WNn.36246$rU6.2337(a)newsfe10.iad>: >>> >>>>Jan Panteltje wrote: >>>> >>>>> On a sunny day (Wed, 02 Jun 2010 17:02:45 -0700) it happened John Larkin >>>>> <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote in >>>>> <tjrd06hpdgiafmof0hq05devdqebcecd06(a)4ax.com>: >>>>> >>>>> >>>>>>I think I did all this right... >>>>>> >>>>>>ftp://jjlarkin.lmi.net/C-mult_bb.JPG >>>>>> >>>>>>ftp://jjlarkin.lmi.net/C-mult_BCX70.JPG >>>>>> >>>>>> >>>>>>John >>>>>> >>>>> >>>>> >>>>> LM317 has > 60 Db ripple rejection? >>>>> Why bother with all this? >>>>> >>>>Head room ? >>> >>>Yes head room is better with an emittor follower, >>>but I think he had free choice of input voltage (a wallwart). >>> >> >>I'm using a 15-volt wart that we stock, and going to a 24-volt one >>would push up the dissipation on other regulators. So I want a >>super-low-noise, low-power LDO. >> >>This is what I did: >> >>ftp://jjlarkin.lmi.net/P14_reg.gif >> >>which is maybe not too bad. The opamp has PSRR rejection better than >>the Early feedthrough of an NPN, and the 15 ohm resistor makes a lower >>corner with the output caps than would 2 ohms of Re. And it regulates >>and current limits. >> >>A 2-stage c-mult might be better in other situations, or maybe an LDO >>followed by one c-mult. > >My eyes would burn, trying to work with that colour set ;) Especially >the black background, the stuff would be floating, drifting in space >for me after a while. > >Grant. That's historical around here, don't know why. We're used to it. Anybody can change it if they like, easy in PADS. John
From: dagmargoodboat on 4 Jun 2010 20:32
On Jun 4, 10:11 am, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Fri, 04 Jun 2010 09:10:03 GMT, Jan Panteltje > > > > <pNaonStpealm...(a)yahoo.com> wrote: > >On a sunny day (Thu, 03 Jun 2010 18:37:42 -0400) it happened Jamie > ><jamie_ka1lpa_not_valid_after_ka1l...(a)charter.net> wrote in > ><S4WNn.36246$rU6.2...(a)newsfe10.iad>: > > >>Jan Panteltje wrote: > > >>> On a sunny day (Wed, 02 Jun 2010 17:02:45 -0700) it happened John Larkin > >>> <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote in > >>> <tjrd06hpdgiafmof0hq05devdqebcec...(a)4ax.com>: > > >>>>I think I did all this right... > > >>>>ftp://jjlarkin.lmi.net/C-mult_bb.JPG > > >>>>ftp://jjlarkin.lmi.net/C-mult_BCX70.JPG > > >>>>John > > >>> LM317 has > 60 Db ripple rejection? > >>> Why bother with all this? > > >>Head room ? > > >Yes head room is better with an emittor follower, > >but I think he had free choice of input voltage (a wallwart). > > I'm using a 15-volt wart that we stock, and going to a 24-volt one > would push up the dissipation on other regulators. So I want a > super-low-noise, low-power LDO. > > This is what I did: > > ftp://jjlarkin.lmi.net/P14_reg.gif > > which is maybe not too bad. The opamp has PSRR rejection better than > the Early feedthrough of an NPN, and the 15 ohm resistor makes a lower > corner with the output caps than would 2 ohms of Re. And it regulates > and current limits. > > A 2-stage c-mult might be better in other situations, or maybe an LDO > followed by one c-mult. > > John Or a c-mult front-end to your L(arkin)LDO. 1k+10uF attenuates 1kHz 50:1, says LTSpice, at the cost of 0.8v. That makes everything easy. James |