Using 1N4001 as Zener Diode

[Ross Mac]

Looks like a reverse blocking 11.4V Zener to me.

I agree...It kind of looks like a custom zener!....Ross

 

[Ross Mac]

I tried to simulate it in Spice and the computer started to smoke

You know Baphomet, a bunch of us may end up in the garage tonight simulating
this damm thing...it should be simple....famous last words!.....Ross

 

[Jim Thompson]

On Mon, 17 Nov 2003 23:21:31 GMT, "Ross Mac"

[snip]

You have to wonder why they did not use an 11 volt zener instead of a 10
volt and 2 1N4004's, unless the additional .2 to .4 volts were
important....which I can't see right now....I don't have a data sheet on
that SCR but perhaps it needed a little more voltage....guess I will have to
study this one a bit more too....Ross

Could be for TC reasons. Zeners above 5V have a positive TC, diodes
have a negative TC.

...Jim Thompson

 

[Ross Mac]

On Mon, 17 Nov 2003 23:21:31 GMT, "Ross Mac"

[snip]

You have to wonder why they did not use an 11 volt zener instead of a 10
volt and 2 1N4004's, unless the additional .2 to .4 volts were
important....which I can't see right now....I don't have a data sheet on
that SCR but perhaps it needed a little more voltage....guess I will have to
study this one a bit more too....Ross

Could be for TC reasons. Zeners above 5V have a positive TC, diodes
have a negative TC.

...Jim Thompson

It sounds to me like you hit the nail on the head Jim....since this device
most probably gets pretty warm under heavy use it makes a lot of sense. And
hey, I found it for 18 bucks at a camera shop. I also found a link that
somewhat speaks exactly to your comment.....good one...that one went right
past me....here is the link... http://www.microsemi.com/micnotes/205.pdf
And hey, I like to cook with wine too....on mushrooms
especially....yummmm.....Ross

 

[Jim Thompson]

On Mon, 17 Nov 2003 23:21:31 GMT, "Ross Mac"

[snip]

You have to wonder why they did not use an 11 volt zener instead of a 10
volt and 2 1N4004's, unless the additional .2 to .4 volts were
important....which I can't see right now....I don't have a data sheet on
that SCR but perhaps it needed a little more voltage....guess I will have to
study this one a bit more too....Ross

Could be for TC reasons. Zeners above 5V have a positive TC, diodes
have a negative TC.

...Jim Thompson

[snip]
It sounds to me like you hit the nail on the head Jim....since this device
most probably gets pretty warm under heavy use it makes a lot of sense. And
hey, I found it for 18 bucks at a camera shop. I also found a link that
somewhat speaks exactly to your comment.....good one...that one went right
past me....here is the link... http://www.microsemi.com/micnotes/205.pdf
And hey, I like to cook with wine too....on mushrooms
especially....yummmm.....Ross

My rule-of-thumb for zeners, while not perfect, is fairly close:

TCz = (Vz-5)mV/°C

for diodes:

TCd = -2mV/°C

I have a *little* experience in that area: At Motorola, in the '60's,
my nickname was vBE-Thompson, since I fixed everything with diodes. I
even have some patents on TC-ing alternator regulators.

Mushrooms in wine sauce over filet = To Die For ;-)

...Jim Thompson

 

[Ross Mac]

On Mon, 17 Nov 2003 23:21:31 GMT, "Ross Mac"

[snip]

You have to wonder why they did not use an 11 volt zener instead of a 10
volt and 2 1N4004's, unless the additional .2 to .4 volts were
important....which I can't see right now....I don't have a data sheet on
that SCR but perhaps it needed a little more voltage....guess I will

have
to

study this one a bit more too....Ross


Could be for TC reasons. Zeners above 5V have a positive TC, diodes
have a negative TC.

...Jim Thompson

[snip]
It sounds to me like you hit the nail on the head Jim....since this device
most probably gets pretty warm under heavy use it makes a lot of sense. And
hey, I found it for 18 bucks at a camera shop. I also found a link that
somewhat speaks exactly to your comment.....good one...that one went right
past me....here is the link... http://www.microsemi.com/micnotes/205.pdf
And hey, I like to cook with wine too....on mushrooms
especially....yummmm.....Ross

My rule-of-thumb for zeners, while not perfect, is fairly close:

TCz = (Vz-5)mV/°C

for diodes:

TCd = -2mV/°C

I have a *little* experience in that area: At Motorola, in the '60's,
my nickname was vBE-Thompson, since I fixed everything with diodes. I
even have some patents on TC-ing alternator regulators.

Mushrooms in wine sauce over filet = To Die For ;-)

...Jim Thompson

Thanks for the formulas, I figured you must be the diode man to know them so
intimately....
......and hey...mushrooms in wine and butter sauce spread over a
filet...can't argue that formula either....I better put the potatoes on now!
I guess I will be off to the kitchen to prepare a meal for the football game
tonight....thanks for the tips Jim, Ross

 

[Jim Weir]

Jim...

We went through a long song and dance to show that the crossover from -tc to +tc
was just a bit above 6 volts (in 1966). Have things dropped to 5 volts now?

Jim


Jim Thompson <[email protected]>
shared these priceless pearls of wisdom:


->
->Could be for TC reasons. Zeners above 5V have a positive TC, diodes
->have a negative TC.
->
-> ...Jim Thompson

 

[Jim Thompson]

Jim...

We went through a long song and dance to show that the crossover from -tc to +tc
was just a bit above 6 volts (in 1966). Have things dropped to 5 volts now?

Jim


Jim Thompson <[email protected]>
shared these priceless pearls of wisdom:


->
->Could be for TC reasons. Zeners above 5V have a positive TC, diodes
->have a negative TC.
->
-> ...Jim Thompson

That's just my old rule-of-thumb. 6V works even better with the OP's
circuit ;-)

...Jim Thompson

 

[Bob Parker]

That approach is now glorified with the name, "evolutionary design".

I thought it was called "empirical clairvoyance"....

Bob

 

[Rich Grise]

[old news, stupid sigs, and angle bracket pyramids, left behind by
string of
bottom-feeder^H^H^H^H^H^Hposters, snipped]

The 1N4001s are there to temperature-compensate the zener. They have
opposite
temperature coefficients, but WAGing from the circuit, I'd say that the
zeners TC is probalby closer to -2x the 1N4001's than -1x. And what the
transistor's for is to amplify current. And the diodes NEVER have more
than
a forward diode drop across them in the forward direction (albeit that
drop
might get up to some volts before the diode explodes) until they open.
The
whole string conducts. I'll have to look at the circuit more to say any
more;
I didn't memorize it yet! ;-D

Cheers!
Rich