Bitrex wrote:> The idea is that the amplified output of the second differential pair > will be approximately the _derivative_ of the tanh function with respect > to the reference voltage, or sec^2h(vid), or tanh^2(vid) - 1, which is > also inverted to get -tanh^2(vid) + 1. Then it's added in the > multiplier to cancel the tanh^2 terms and get 1, or a voltage that's > stable with respect to variations in the reference. In practice I'm not > getting 100mv out as I expected but the multiplier does seem to put out > a stable voltage, with 1V P-P at 1000 Hz bouncing on the supply a FFT on > the output shows the first harmonic down -115 dB, which is about the > PSRR of the output op amp. >I meant the derivative is 1 - tanh^2....I think in the circuit however things are added up the correct way. I'll have to check again!
C-multiplier again
Started by ●May 22, 2010
Reply by ●May 25, 20102010-05-25
Reply by ●May 26, 20102010-05-26
Bitrex wrote:> Bitrex wrote: > >> The idea is that the amplified output of the second differential pair >> will be approximately the _derivative_ of the tanh function with >> respect to the reference voltage, or sec^2h(vid), or tanh^2(vid) - 1, >> which is also inverted to get -tanh^2(vid) + 1. Then it's added in >> the multiplier to cancel the tanh^2 terms and get 1, or a voltage >> that's stable with respect to variations in the reference. In >> practice I'm not getting 100mv out as I expected but the multiplier >> does seem to put out a stable voltage, with 1V P-P at 1000 Hz bouncing >> on the supply a FFT on the output shows the first harmonic down -115 >> dB, which is about the PSRR of the output op amp. >> > > I meant the derivative is 1 - tanh^2....I think in the circuit however > things are added up the correct way. I'll have to check again!Eh, the idea doesn't seem to be working out - the output is actually better without the multiplier in the cicuit! It looked good on paper, oh well. :(
Reply by ●May 26, 20102010-05-26
"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message news:90lov5d1lvqrrhqihs9gehltl79h9920at@4ax.com...> I do this occasionally, with transistors or fets: > > <snip>Durr... I've even been known to do it with tubes. ;-) Tim -- Deep Friar: a very philosophical monk. Website: http://webpages.charter.net/dawill/tmoranwms
Reply by ●May 26, 20102010-05-26
John Larkin <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:> On Tue, 25 May 2010 21:48:13 GMT, Mike <spam@me.not> wrote: > >>> I did about the same, similar results. >>> >>> ftp://jjlarkin.lmi.net/C-multiplier.gif >> >>Phil mentioned many spice programs don't handle this very well. Using >>the data from his later post showed the results with LTspice are not >>usable. >> >>Mike > > The question is whether the Early voltage slope is realistic. I don't > know. I suppose I should breadboard some parts but... the Gerbers are > gone!> JohnYou could do a quick test. Use the grounded base circuit you just posted, with the base lead soldered to copperclad. Apply appropriate bias and signal, and measure the result. I modeled the MPSA14. It took a 20MEG in parallel with 5nF, in series with 800pF in parallel with 100k. I then compared a single 2N4401 with the P. Hobbs model. The results with LTspice are completely unrealistic. The files are archived in 3CBA32DC.ZIP, posted to abse with the title "More E-F Ripple Filter Simulations". Mike
Reply by ●May 26, 20102010-05-26
John Larkin wrote...> >On 23 May 2010 16:54:54 -0700, Winfield Hill ><Winfield_member@newsguy.com> wrote: > >>dagmargoodboat@yahoo.com wrote... >>> >>> This shunt filter only needs 200mV headroom: >>> >>> FIG. 2 >>> R1 >>>+15V >--+------------------/\/\/\--------+--> Vout 14.8v >>> | 5 | >>> | | >>> | .-------+------+--------+ >>> | | | | | >>> | | | R6 | >>> | | | 1k | >>> | R3 R5 | |<' Q3 >>> | 2.7M 10K +------| 2n3906 >>> | | | | |\ >>> | | | |/ Q2 | >>> | | +----| 2n3904 | >>> | | | |>. | >>> | C1 | |<' | | >>> '---||---+----| Q1 '--------+ >>> 10uF |\ 2n3906 | >>> | R4 >>> | 4.7R >>> | | >>> ------+----------------+---- >> >> Nice ASCII art. Is fig 2 from your feverish brain? >> >> I see your idea, invert the ripple and subtract it out. >> Good. To do that the cancellation amplifier needs to >> be biased class A, so it can work over the entire ripple >> range. It should continuously draw current from the >> supply through R1, and superimpose the inverted ripple >> signal on top of that. R4 can be trimmed to optimize. >> The new R7 should be sized to handle the p-p ripple. >> >> Then John's delicate C-multiplier filter can follower, >> with all the heavy lifting having been done. >> >> +15V >--+-----------------/\/\/\--------+--> Vout 14.8v >> | 5 | >> | | >> | .------+------+--------+ >> | | | | | >> | | | R6 | >> | | | 1k | >> | R3 R5 | |<' Q3 >> | 2.7M 10K +------| 2n4403 >> | | | | |\ >> | | | |/ Q2 | >> | C1 | +----| 2n3904 | >> '---||---+ | |>. | >> 10uF | |<' | | >> +----| Q1 '--------+ >> | |\ 2n3906 | >> R7 | R4 >> TBD 27k | 4.7R >> | | | >> --+------+---------------+---- > > > 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. -- Thanks, - Win
Reply by ●May 26, 20102010-05-26
On May 26, 8:26=A0am, Winfield Hill <Winfield_mem...@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) > > =A0+15V >--+--------+--/\/\--+-----> Vout 14.8v > =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0| =A04.7R =A0| > =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 R3 =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A02.7M =A0 =A0 =A0 | > =A0 =A0 =A0 =A0 =A0} =A0 =A0 =A0 =A0| =A0 =A0 =A0 _| > =A0 =A0 =A0 =A0 =A0| =A0 C1 =A0 +------| =A0\ =A0 =A0 =A0 > =A0 =A0 =A0 =A0 =A0'---||---+ =A0 =A0 =A0| =A0 >--+---, > =A0 =A0 =A0 =A0 =A0 =A0 10uF =A0| =A0 ,--|__/ =A0 | =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 | =A0 =A0| =A0 =A0| =A0 | > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0R7 =A0 '--- |----' =A0R4 > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0TBD 27k =A0 =A0 | =A0 =A0 =A0 4.7R > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 --+--------+--------+---- > > =A0I see your idea, not bad. =A0It's a nice simplification of this, > =A0incorporating the current-sinking transistor into the opamp. > > =A0+15V >--+--------+--------+----/\/\--+-----> Vout 14.8v > =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0| =A0 =A04.7R =A0| > =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A0 R3 =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0 =A0| =A0 =A0 =A02.7M =A0 =A0 =A0 | =A0 =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0 =A0} =A0 =A0 =A0 =A0| =A0 =A0 =A0 _| =A0 =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0 =A0| =A0 C1 =A0 +------| =A0\ =A0 =A0 =A0 |/ > =A0 =A0 =A0 =A0 =A0'---||---+ =A0 =A0 =A0| =A0 >------| > =A0 =A0 =A0 =A0 =A0 =A0 10uF =A0| =A0 ,--|__/ =A0 =A0 =A0 |\V > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 | =A0 =A0| =A0 =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0R7 =A0 '--- |----------+ > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 TBD =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 =A0| > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A027k =A0 =A0 =A0 | =A0 =A0 =A0 =A0 R4 > =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 4.=7R> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A0 =A0 =A0| =A0 =A0 =A0 =A0 ==A0|> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 --+--------+----------+---- > > =A0This scheme is DC regulating as well. =A0The class-A current > =A0is 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. 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.) -- Cheers, James Arthur
Reply by ●May 26, 20102010-05-26
On Wed, 26 May 2010 06:56:18 -0700 (PDT), dagmargoodboat@yahoo.com wrote:>On May 26, 8:26�am, Winfield Hill <Winfield_mem...@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. John
Reply by ●May 26, 20102010-05-26
On May 26, 10:02=A0am, John Larkin wrote:> On Wed, 26 May 2010 06:56:18 -0700 (PDT), dagmargoodb...@yahoo.com > wrote: > > > > >On May 26, 8:26=EF=BF=BDam, Winfield Hill =A0<Winfield_mem...@newsguy.co=m>> >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. =A0John'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 =3D 5 ohms, load regulation =3D zip.> >The multi-pole BJT C-mult looks great for feather-weight and constant > >loads. =A0If 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? =A0(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. -- Cheers, James Arthur
Reply by ●May 26, 20102010-05-26
On Wed, 26 May 2010 07:30:39 -0700 (PDT), dagmargoodboat@yahoo.com wrote:>On May 26, 10:02�am, John Larkin wrote: >> On Wed, 26 May 2010 06:56:18 -0700 (PDT), dagmargoodb...@yahoo.com >> wrote: >> >> >> >> >On May 26, 8:26�am, Winfield Hill �<Winfield_mem...@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." John
Reply by ●May 26, 20102010-05-26
John Larkin a �crit :> On Wed, 26 May 2010 06:56:18 -0700 (PDT), dagmargoodboat@yahoo.com > wrote: >...> 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. >And a gmail account? -- Thanks, Fred.
