C-multiplier again
in [Design]
|
Prev: Futuristic weapon question: Anti-matter-gun, would it have a signature ?
Next: EEVblog Live Event
From: John Larkin on 26 May 2010 16:53 On Wed, 26 May 2010 13:03:33 -0700 (PDT), dagmargoodboat(a)yahoo.com wrote: >On May 26, 10:57�am, Mike <s...(a)me.not> wrote: >> Winfield Hill �<Winfield_mem...(a)newsguy.com> wrote: >> >> [...] >> >> >> >> > �I see your idea, not bad. �It's a nice simplification of this, >> > �incorporating the current-sinking transistor into the opamp. >> >> > �+15V >--+--------+--------+----/\/\--+-----> Vout 14.8v >> > � � � � �| � � � �| � � � �| � �4.7R �| >> > � � � � �| � � � R3 � � � �| � � � � �| >> > � � � � �| � � �2.7M � � � | � � � � �| >> > � � � � �} � � � �| � � � _| � � � � �| >> > � � � � �| � C1 � +------| �\ � � � |/ >> > � � � � �'---||---+ � � �| � >------| >> > � � � � � � 10uF �| � ,--|__/ � � � |\V >> > � � � � � � � � � | � | � �| � � � � �| >> > � � � � � � � � �R7 � '--- |----------+ >> > � � � � � � � � TBD � � � �| � � � � �| >> > � � � � � � � � �27k � � � | � � � � R4 >> > � � � � � � � � � | � � � �| � � � � 4.7R >> > � � � � � � � � � | � � � �| � � � � �| >> > � � � � � � � � --+--------+----------+---- >> >> > �This scheme is DC regulating as well. �The class-A current >> > �is set by R3 and R7, so the dc voltage drop is fixed. >> >> Cancellation schemes give a 6dB/octave drop to a notch frequency, then a >> 6dB/octave rise. The depth of the notch is extremely sensitive to the >> emitter resistance and probably the temperature of the transistor. Some >> examples may show large amounts of second harmonic distortion on the >> output. This does not appear on the frequency analysis plot. >> >> In this example, the notch frequency is about 2KHz with a depth of -92dB. >> Try changing the emitter resistance to get an idea of how critical it is. >> >> I don't think you want to rely on this method for any more than a minor >> amount of cancellation, say 20 dB or thereabouts. >> >> Mike > ><snip LTSpice model> > >20dB sounds about right. The advantages of this approach are low drop- >out voltage and superior low-frequency noise cancellation (compared to >practical passive equivalents). > >A big part of the dynamic limitation is the f.f. network rolling off. >If you change C1 to 100uF, and tack 100uF on the output to cover the >high-end, overall performance is much improved--nearly as good as a >passive version using 10,000uF caps, and a lot smaller. > >For super massive attenuation of input noise and ripple, other >approaches are better. > >If John could knock down that 50mV switcher ripple with an LC at the >input, that's a bonus. But he won't--The Brat would kill him. No, I survived. The Gerbered board had... Wall wart connector Polyfuse Transzorb 10 uF ceramic 47 uH inductor two 10 uF ceramics and one 120 uF polymer aluminum to make "+15 volts." That's 12 dB/octave starting at about 2 KHz. Then the LM8261 low-noise LDO reg, which has its own 15 ohms + 2x10uF + 120uF at its output. I also use two Hobbsonian c-multipliers in other supplies that don't need LDO or regulation. Paranoia, groveling for nanovolts. But I really need to measure some actual c-multiplier circuits to see what the Early slopes are like. Could be that LT Spice is grossly pessimistic. I note here that everyone, including myself, would rather sit in a swivel chair and simulate and theorize, than get up and solder and measure. John
From: Spehro Pefhany on 26 May 2010 17:17 On Wed, 26 May 2010 13:53:55 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Wed, 26 May 2010 13:03:33 -0700 (PDT), dagmargoodboat(a)yahoo.com >wrote: > >>On May 26, 10:57�am, Mike <s...(a)me.not> wrote: >>> Winfield Hill �<Winfield_mem...(a)newsguy.com> wrote: >>> >>> [...] >>> >>> >>> >>> > �I see your idea, not bad. �It's a nice simplification of this, >>> > �incorporating the current-sinking transistor into the opamp. >>> >>> > �+15V >--+--------+--------+----/\/\--+-----> Vout 14.8v >>> > � � � � �| � � � �| � � � �| � �4.7R �| >>> > � � � � �| � � � R3 � � � �| � � � � �| >>> > � � � � �| � � �2.7M � � � | � � � � �| >>> > � � � � �} � � � �| � � � _| � � � � �| >>> > � � � � �| � C1 � +------| �\ � � � |/ >>> > � � � � �'---||---+ � � �| � >------| >>> > � � � � � � 10uF �| � ,--|__/ � � � |\V >>> > � � � � � � � � � | � | � �| � � � � �| >>> > � � � � � � � � �R7 � '--- |----------+ >>> > � � � � � � � � TBD � � � �| � � � � �| >>> > � � � � � � � � �27k � � � | � � � � R4 >>> > � � � � � � � � � | � � � �| � � � � 4.7R >>> > � � � � � � � � � | � � � �| � � � � �| >>> > � � � � � � � � --+--------+----------+---- >>> >>> > �This scheme is DC regulating as well. �The class-A current >>> > �is set by R3 and R7, so the dc voltage drop is fixed. >>> >>> Cancellation schemes give a 6dB/octave drop to a notch frequency, then a >>> 6dB/octave rise. The depth of the notch is extremely sensitive to the >>> emitter resistance and probably the temperature of the transistor. Some >>> examples may show large amounts of second harmonic distortion on the >>> output. This does not appear on the frequency analysis plot. >>> >>> In this example, the notch frequency is about 2KHz with a depth of -92dB. >>> Try changing the emitter resistance to get an idea of how critical it is. >>> >>> I don't think you want to rely on this method for any more than a minor >>> amount of cancellation, say 20 dB or thereabouts. >>> >>> Mike >> >><snip LTSpice model> >> >>20dB sounds about right. The advantages of this approach are low drop- >>out voltage and superior low-frequency noise cancellation (compared to >>practical passive equivalents). >> >>A big part of the dynamic limitation is the f.f. network rolling off. >>If you change C1 to 100uF, and tack 100uF on the output to cover the >>high-end, overall performance is much improved--nearly as good as a >>passive version using 10,000uF caps, and a lot smaller. >> >>For super massive attenuation of input noise and ripple, other >>approaches are better. >> >>If John could knock down that 50mV switcher ripple with an LC at the >>input, that's a bonus. But he won't--The Brat would kill him. > >No, I survived. The Gerbered board had... > >Wall wart connector > >Polyfuse > >Transzorb > >10 uF ceramic > >47 uH inductor > >two 10 uF ceramics and one 120 uF polymer aluminum to make "+15 >volts." That's 12 dB/octave starting at about 2 KHz. > >Then the LM8261 low-noise LDO reg, which has its own 15 ohms + 2x10uF >+ 120uF at its output. Using an LM8261 op-amp to make an LDO?
From: John Larkin on 26 May 2010 17:27 On Wed, 26 May 2010 17:17:32 -0400, Spehro Pefhany <speffSNIP(a)interlogDOTyou.knowwhat> wrote: >On Wed, 26 May 2010 13:53:55 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Wed, 26 May 2010 13:03:33 -0700 (PDT), dagmargoodboat(a)yahoo.com >>wrote: >> >>>On May 26, 10:57�am, Mike <s...(a)me.not> wrote: >>>> Winfield Hill �<Winfield_mem...(a)newsguy.com> wrote: >>>> >>>> [...] >>>> >>>> >>>> >>>> > �I see your idea, not bad. �It's a nice simplification of this, >>>> > �incorporating the current-sinking transistor into the opamp. >>>> >>>> > �+15V >--+--------+--------+----/\/\--+-----> Vout 14.8v >>>> > � � � � �| � � � �| � � � �| � �4.7R �| >>>> > � � � � �| � � � R3 � � � �| � � � � �| >>>> > � � � � �| � � �2.7M � � � | � � � � �| >>>> > � � � � �} � � � �| � � � _| � � � � �| >>>> > � � � � �| � C1 � +------| �\ � � � |/ >>>> > � � � � �'---||---+ � � �| � >------| >>>> > � � � � � � 10uF �| � ,--|__/ � � � |\V >>>> > � � � � � � � � � | � | � �| � � � � �| >>>> > � � � � � � � � �R7 � '--- |----------+ >>>> > � � � � � � � � TBD � � � �| � � � � �| >>>> > � � � � � � � � �27k � � � | � � � � R4 >>>> > � � � � � � � � � | � � � �| � � � � 4.7R >>>> > � � � � � � � � � | � � � �| � � � � �| >>>> > � � � � � � � � --+--------+----------+---- >>>> >>>> > �This scheme is DC regulating as well. �The class-A current >>>> > �is set by R3 and R7, so the dc voltage drop is fixed. >>>> >>>> Cancellation schemes give a 6dB/octave drop to a notch frequency, then a >>>> 6dB/octave rise. The depth of the notch is extremely sensitive to the >>>> emitter resistance and probably the temperature of the transistor. Some >>>> examples may show large amounts of second harmonic distortion on the >>>> output. This does not appear on the frequency analysis plot. >>>> >>>> In this example, the notch frequency is about 2KHz with a depth of -92dB. >>>> Try changing the emitter resistance to get an idea of how critical it is. >>>> >>>> I don't think you want to rely on this method for any more than a minor >>>> amount of cancellation, say 20 dB or thereabouts. >>>> >>>> Mike >>> >>><snip LTSpice model> >>> >>>20dB sounds about right. The advantages of this approach are low drop- >>>out voltage and superior low-frequency noise cancellation (compared to >>>practical passive equivalents). >>> >>>A big part of the dynamic limitation is the f.f. network rolling off. >>>If you change C1 to 100uF, and tack 100uF on the output to cover the >>>high-end, overall performance is much improved--nearly as good as a >>>passive version using 10,000uF caps, and a lot smaller. >>> >>>For super massive attenuation of input noise and ripple, other >>>approaches are better. >>> >>>If John could knock down that 50mV switcher ripple with an LC at the >>>input, that's a bonus. But he won't--The Brat would kill him. >> >>No, I survived. The Gerbered board had... >> >>Wall wart connector >> >>Polyfuse >> >>Transzorb >> >>10 uF ceramic >> >>47 uH inductor >> >>two 10 uF ceramics and one 120 uF polymer aluminum to make "+15 >>volts." That's 12 dB/octave starting at about 2 KHz. >> >>Then the LM8261 low-noise LDO reg, which has its own 15 ohms + 2x10uF >>+ 120uF at its output. > >Using an LM8261 op-amp to make an LDO? Yup, it's this one: ftp://jjlarkin.lmi.net/P14_reg.gif (hope you can see it; some people are reporting trouble accessing my FTP files) The LM8261 is a great part. Pretty good RRIO opamp, 32 volts, 21 MHz, tons of current drive, stable into any capacitive load. John
From: Michael A. Terrell on 26 May 2010 20:29 John Larkin wrote: > > On Wed, 26 May 2010 07:30:39 -0700 (PDT), dagmargoodboat(a)yahoo.com > wrote: > > >On May 26, 10:02 am, John Larkin wrote: > >> On Wed, 26 May 2010 06:56:18 -0700 (PDT), dagmargoodb...(a)yahoo.com > >> wrote: > >> > >> > >> > >> >On May 26, 8:26�am, Winfield Hill <Winfield_mem...(a)newsguy.com> > >> >wrote: > >> >> John Larkin wrote... > >> > >> ><snip> > >> > >> >> > How about an opamp powered from Vout, with a resistor from the opamp > >> >> > output to ground? Let the opamp supply current fight the output > >> >> > ripple. That's thermally stable, simple, high gain, and tunable. > >> > >> >> > (except I need regulation, too) > >> > >> +15V >--+--------+--/\/\--+-----> Vout 14.8v > >> | | 4.7R | > >> | R3 | > >> | 2.7M | > >> } | _| > >> | C1 +------| \ > >> '---||---+ | >--+---, > >> 10uF | ,--|__/ | | > >> | | | | | > >> R7 '--- |----' R4 > >> TBD 27k | 4.7R > >> | | | > >> --+--------+--------+---- > > > >> I see your idea, not bad. It's a nice simplification of this, > >> incorporating the current-sinking transistor into the opamp. > > > >> +15V >--+--------+--------+----/\/\--+-----> Vout 14.8v > >> | | | 4.7R | > >> | R3 | | > >> | 2.7M | | > >> } | _| | > >> | C1 +------| \ |/ > >> '---||---+ | >------| > >> 10uF | ,--|__/ |\V > >> | | | | > >> R7 '--- |----------+ > >> TBD | | > >> 27k | R4 > >> | | 4.7R > >> | | | > >> --+--------+----------+---- > > > >> >> This scheme is DC regulating as well. The class-A current > >> >> is set by R3 and R7, so the dc voltage drop is fixed. > >> > >> >Both give line regulation, true. John's problem seems to be that he > >> >needs(?) load regulation too. > >> > >> If there's no voltage reference, there's no regulation. > > > >The +15v is the reference. So, maybe more accurately, these circuits > >don't regulate, but they preserve the +15v input's line regulation. > >rOut = 5 ohms, load regulation = zip. > > > > > >> >The multi-pole BJT C-mult looks great for feather-weight and constant > >> >loads. If the ultra-clean part of the load is separable, I'd do that. > >> > >> >If John really needs low-dropout, 15mA, tight load regulation, and low > >> >noise, my best shot so far is to bootstrap the op-amp's supplies on > >> >the Gerber'd "filtered-reference feeding a R-R op-amp" thing he linked > >> >to, to circumvent the op amp's CMRR / PSRR feeding thru. > >> > >> >Or, I guess, feed the op amp with a steady voltage, e.g., to make an > >> >ultra-clean supply, start with an ultra-clean supply... > >> > >> >Or cascade a couple such op-amp stages, each feeding the next, each > >> >stage improving PSRR by whatever it can muster. 50-60dB? (I don't > >> >really trust op amps to have low noise and amazing PSRRs and CMRRs > >> >over frequency, but then I've not looked at all the latest and > >> >greatest.) > >> > >> All I want is a SOT-23 LDO regulator with 1 nv/rthz noise, 140 dB PSRR > >> to 1 MHz, and not made by Maxim. > > > >Heathen. > > If you don't mind, I prefer "barbarian." I thought you preferred 'Mary'? :) -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge.
From: MooseFET on 26 May 2010 21:06
On May 26, 7:02 am, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Wed, 26 May 2010 06:56:18 -0700 (PDT), dagmargoodb...(a)yahoo.com > wrote: > > > > >On May 26, 8:26 am, Winfield Hill <Winfield_mem...(a)newsguy.com> > >wrote: > >> John Larkin wrote... > > ><snip> > > >> > How about an opamp powered from Vout, with a resistor from the opamp > >> > output to ground? Let the opamp supply current fight the output > >> > ripple. That's thermally stable, simple, high gain, and tunable. > > >> > (except I need regulation, too) > > >> +15V >--+--------+--/\/\--+-----> Vout 14.8v > >> | | 4.7R | > >> | R3 | > >> | 2.7M | > >> } | _| > >> | C1 +------| \ > >> '---||---+ | >--+---, > >> 10uF | ,--|__/ | | > >> | | | | | > >> R7 '--- |----' R4 > >> TBD 27k | 4.7R > >> | | | > >> --+--------+--------+---- > > >> I see your idea, not bad. It's a nice simplification of this, > >> incorporating the current-sinking transistor into the opamp. > > >> +15V >--+--------+--------+----/\/\--+-----> Vout 14.8v > >> | | | 4.7R | > >> | R3 | | > >> | 2.7M | | > >> } | _| | > >> | C1 +------| \ |/ > >> '---||---+ | >------| > >> 10uF | ,--|__/ |\V > >> | | | | > >> R7 '--- |----------+ > >> TBD | | > >> 27k | R4 > >> | | 4.7R > >> | | | > >> --+--------+----------+---- > > >> This scheme is DC regulating as well. The class-A current > >> is set by R3 and R7, so the dc voltage drop is fixed. > > >Both give line regulation, true. John's problem seems to be that he > >needs(?) load regulation too. > > If there's no voltage reference, there's no regulation. > > > > > > >The multi-pole BJT C-mult looks great for feather-weight and constant > >loads. If the ultra-clean part of the load is separable, I'd do that. > > >If John really needs low-dropout, 15mA, tight load regulation, and low > >noise, my best shot so far is to bootstrap the op-amp's supplies on > >the Gerber'd "filtered-reference feeding a R-R op-amp" thing he linked > >to, to circumvent the op amp's CMRR / PSRR feeding thru. > > >Or, I guess, feed the op amp with a steady voltage, e.g., to make an > >ultra-clean supply, start with an ultra-clean supply... > > >Or cascade a couple such op-amp stages, each feeding the next, each > >stage improving PSRR by whatever it can muster. 50-60dB? (I don't > >really trust op amps to have low noise and amazing PSRRs and CMRRs > >over frequency, but then I've not looked at all the latest and > >greatest.) > > All I want is a SOT-23 LDO regulator with 1 nv/rthz noise, 140 dB PSRR > to 1 MHz, and not made by Maxim. I have an interesting idea. How about a blue LED as the reference. It is a forward biased diode so it may be low noise. > > John |