Hello Dave, Harold, Barry et all,

    thank you very much for the marvellous explanations.

>If you are referring to the figure titled "1.5V to 5V Bootstrapped
>Step-Up Converter", the term is used to mean that the LT1073 starts up
>from the 1.5V battery, but once it begins to develop the regulated 5V
>output, it draws its internal operating power from the generated 5V
>output rather than from the battery.

    Yes, I'm trying to make this circuit to work but I don't have the right
inductors. The cheap inductors doesn't work very well and I only have
"professional" (:^) inductors of 100uH.

    By target is a circuit to obtain 5V @ 100-150mA from two alkaline (2 x
1.5V) or 2 NiMH (2 x 1.2V) cells. I'm trying with the LT1173-5 and various
inductors/caps/resistors, but can't suck more than 80mA when the input drops
bellow 2.5V. :(

    Sugestions? Maybe another thread...

    Best regards,

    Brusque

-----------------------------------
Edson Brusque
Research and Development
C.I.Tronics Lighting Designers Ltda
Blumenau  -  SC  -  Brazil
www.citronics.com.br
-----------------------------------


"Bootstrap" is one of those poorly-defined electronic "slang" terms that
has its roots in ancient history; it probably goes back at least to the
1930's.  In general it is used to denote a method of circuit operation
in which a generated output, of whatever sort, is used to assist, in
some way, the generation process.

Example: in a transistor circuit sometimes called a "bootstrapped
emitter follower", the output of an emitter follower (i.e., common
collector) amplifier stage is fed back via a coupling capacitor to the
base-bias resistor network, which has the effect of raising the input
impedance of the stage.

Another example: in some audio power amplifier designs, the amplifier
output is sometimes fed back via a coupling capacitor to the bias
network which supplies pull-up drive to the output stage.  This kind of
"bootstrapping" allows the stage drive to momentarily exceed the (+)
rail voltage on positive output swings, allowing the transistor in the
output stage to be driven closer to saturation; this gives a higher
maximum power output for a given power supply voltage.

Hope this helps a bit...

Dave

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