Re: Reference Voltage Schematic

On Feb 17, 2:15 pm, Gibbo <g...@xxxxxxxxxxxxxxxx> wrote:
James Arthur wrote:
On Feb 17, 10:00 am, Gibbo <g...@xxxxxxxxxxxxxxxx> wrote:

[snip]


Why does the National data *** show Q1 as being either Si or Ge then?

It doesn't, at least not in my copy. Seehttp://www.national.com/ds/LM/LM111.pdf

You're right it doesn't (I was working from memory). It't the TI one
that shows both Qs as Si.

http://focus.ti.com/lit/ds/symlink/lm111.pdf

And the circuit does indeed work with both Qs as Si but with (obviously)
a much lower voltage as FB details.

--
Gibbo

We agree the circuit works per Fred's description when Q1 is
silicon, and we agree the output voltages are quite different for
silicon versus germanium Q1. I measure Uo = 18.18mV with Q2=PN2222a,
Q1=KTC3198, with drift of roughly 0.3% / C, line regulation = 0.9% /
V. With Q1=2n5772, Uo = 6.88mV.

However, the application circuits then make no sense, as this
massive a change in reference voltage would obviously have a huge
impact on the "Low Voltage Adjustable Reference Supply" and the
precision waveform squarer I identified earlier. The reference
voltage would then be only a few times the comparator's offset
voltage, for one thing, and massively dependent on Vbe matching, for
another.

Since the LM311 was originally a National Semiconductor design
("LMxxx," after all) I conclude T.I. copied National's data***, that
some helpful T.I. app engineer noticed the obsolete transistor, and
erred in recommending a substitute Q1. Perhaps he's the same fellow
who left the "dot" off the precision squarer circuit?, which, as
drawn, produces no useful output!

Cheers,
James Arthur

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