It wouldn't work the same. As the load on the circuit increases, the
base current also increases, so the voltage drops both due to the
overall voltage drop, and also due to the increases base drive.
Hopefully keeping the transistor from dropping out (and letting ripple
through).

If you used a MOSFET, you could get gobs of ripple reduction (the
resistor can be much larger), more than with a BJT. But as you increase
the load, the output voltage only tracks the voltage drop, not the
increased load current.

A 78xx regulator would need the ground lead to be less than the output,
unlike a BJT or MOSFET. So you'd need to use a voltage divider (off the
input, to ground). It would track the input voltage, but due to the
voltage divider, to a lesser extent than a BJT or MOSFET.

Friendly regards, Bob

On Thu, Mar 5, 2015, at 07:25 PM, Ryan O'Connor wrote:
> Does it have to be a BJT? What about a mosfet or a 78xx regulator with a
> cap on its adjust pin?
>=20
> Ryan
> On 6/03/2015 4:17 PM, "Bob Blick" <bobblick@ftml.net> wrote:
>=20
> > Hi Ryan,
> > You are right! It does not increase the storage of the filter capacitor=
..
> > If you have an unregulated power supply with a filter capacitor (an
> > old-school DC wall-wart, for example) there will be ripple under load.
> > The greater the load, the greater the ripple. What the described circui=
t
> > can do (with appropriate transistor/resistor/capacitor choices) is
> > maintain the output voltage a little under the lowest peak of the
> > ripple. The ripple on the output is less than, but follows, a multiple
> > of the circuit's capacitor. The nice thing about it is that the output
> > voltage drops with load, so it almost tracks the lower ripple peak,
> > something a 78xx regulator can't do. It also has less insertion loss.
> > Cheerful regards, Bob
> >
> > On Thu, Mar 5, 2015, at 06:50 PM, Ryan O'Connor wrote:
> > > That page is really informative. However, I'm left wondering about th=
e
> > > physics. How can a capacitor which stores charge possibly be "multipl=
ied"
> > > without any additional storage?
> > >
> > > Ryan
> > >
> > > On 6 March 2015 at 02:46, Adam Field <adam@badtech.org> wrote:
> > >
> > > > On Wed, Mar 4, 2015 at 12:17 PM, Bob Blick <bobblick@ftml.net> wrot=
e:
> > > > > Hi Joe,
> > > > > You could use a one transistor pass element to multiply a capacit=
or.
> > Let
> > > > > me see if I can find an example on the web... nope. here's napkin
> > art.
> > > > >
> > > > > Bob
> > > >
> > > > ESP has a good page on the concept:
> > > >
> > > > http://sound.westhost.com/project15.htm

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