On Tue, 05 Aug 2008 08:20:52 -0400, John Popelish
wrote:

I have been building spice models to explore some of the
early linear devices shown in this old data book (back when
National was so proud of their new stuff that they showed
you how they did it). Many do not work by just dropping
generic parts into the schematic, without doing some device
scaling (that is not always shown). But the LM78xx positive
voltage regulator worked fine with no such fiddling.

I am trying to understand how the temperature compensated
voltage reference and error amplifier works. It is not a
structure I recognize as a combination of text book
sections, but does quite a lot with a few devices. I have
attached a screen capture of the schematic (slightly
rearranged from the data book picture , to help me see
function), and the LTspice .asc file.

The part that has captured my attention is Q8,9,11,13 that I
think makes up the heart of the reference voltage generator
and error amplifier, all nicely temperature compensated.

Does anyone recognize a particular designer's tricks, here?
I think this is pretty elegant, if not so obvious.

Splitting hairs, but the Nat Semi original regulator part numbers were
LM104 (204, 304), LM105 (205, 305), 109, 117, 120 etc. The 78xx
nomenclature (and pinout) were Eairchild (uA78xx).

You're refering to the 'Widlar diode' that was developed and employed
in these parts (inventor Robert Widlar). There should be plenty of
stuff out there, as it's in most integrated circuit design course
notes. Check some of Robert Pease's articles - he assumed the role of
'emperor' or policeman of band-gap' reference implimentation at Nat
Semi.

The published schematics were never intended to be anything more than
conceptual, as the cell device characterisrics and scaling are part of
basic reference function and temperature compensation.

RL