Zener diode modeling

"Popcorn" noise.... I remember "back in th good old daze" when every maker of analog op amps was plagued with that and all sorts of ideas as to cause, etc was floating around to no avail. Someone finally found a cure, and if i remember correctly, it was chemical PURITY and CLEANLINESS, especially related to the surface.

To refute someone's statement about zener application (and theory to boot), here is an exact quote from the first page of the Motorola Zener Diode Handbook May 1967:

INTRODUCTION

Product advances and widespread use have converted zener diodes from the exotic components of only a few years ago into ubiquitous elements of engineering practice. In addition to significant advances in zener capability, a host of zener-like devices have joined the designer's arsenal. Temperature compensated diodes, reference diodes, current regulators, and zener transient suppressors provide capabilities not previously available.

Motorola's new Zener Diode Handbook is designed to provide the circuit designer with all of the information necessary for efficient use of zener components. Since the very diversity of zener application precludes a comprehensive index of applications, the Handbook emphasis is on designing with zeners. Proven basic circuits provide a springboard for the designer's own requirements.

In addition to detailed analysis of zener characteristics and their response to electrical and environmental stimuli, the Zener Diode Handbook is a major source of device data. The cross reference, specification, and selection information in Chapter X will greatly aid the designer in his choice of zener components.

** end quote **

I got a little curious and decided to make more current measurements.

• 2N2219, Signetics circa 1980's: about 7.6V E-B, slightly negative slope 0-200uA, sharp knee, no oscillations seen to a few mA. E-C (base open) however, shows those (random) bursts that Win mentioned around 6V, more frequent as the voltage is slowly increased.

• 2N3053, TI circa 1980's: about 7.3V E-B, similar only at lower current

0-100uA. E-C has definite negative slope 700uA to 5mA; no oscillations seen.

• 2N2369A, ST Micro, an RF type as in smallest can made: about 5.3V E-B,

0-200uA rather rounded knee. E-C 5-20uA region definitely negative slope and noisy; no oscillation seen.

These were quick and dirty observations just out of curiosity. However the results make it clear that when the B-C junction is used as an added forward biased junction, that the characteristic of the transistor takes on a whole new character which might be called beta multiplication and enhancement.

From the "Undocumented LTSpice" section of the LT Wiki:

"Bipolar CB avalanche breakdown is modeled in the LTspice Gummel-Poon device:

• BVcbo: C-B breakdown voltage. * nBVcbo: breakdown emission coefficient ; default value = 1? * TBVcbo1: linear temperature coefficient of breakdown voltage. * TBVcbo2: quadratic temperature coefficient of breakdown voltage.

Bipolar BE breakdown is also in the LTspice Gummel-Poon device:

• BVbe: B-E breakdown voltage. * IBVbe: breakdown current at breakdown voltage. * nBVbe: breakdown emission coefficient. "

I haven't tried it (yet).

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

A typical small 10-volt zener has a region where it will make noisy sawtooth oscillations, 50 uA maybe from my memory. As current goes up, you get the asymmetric erratic pulsing thing, decreasing in amplitude as current increases. By the time you get to a few mA, it's nearly symmetrical almost Gaussian wideband noise, a few hundred nV per root Hz.

If you want predictable noise with decent statistics and wideband quality, keep the current up, 5 or 10 mA for a typical 1N758 type.

John

I don't think that's truly avalanche.

And that ain't Gummel-Poon... it's LTspice... just like their "diode" model. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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Hi John, Yeah I guess I was looking for repeatabliity. (I don't want to have to sort diodes...) I've got exactly the pulse into RC in the schematic I posted.

Adding two back to back gives this RC-interuptus signal. Randomly spaced RC's going in both directions.

George H.

That makes lots of signal, but it won't be repeatable and will have rotten statistics. At higher currents, you get lower amplitude but better noise. 300 nv/rthz is easy to amplify... it's hard to find an opamp anywhere that bad.

John

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Hmm, I don't know why, but the circuit seems to be very repeatable. We've sold ~150 units with this noise source in them and looking over my numbers I see rms voltages from 2.5 to 2.0 volts... with most of them at 2.2 Vrms.

I have no idea of the 'physics' behind the numbers... or why other zeners vary so much.

George H.

Well, I've had a quick play, and I guess you're right:-(

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

LTspice has a lot of "finagles" that work _most_of_the_time_ when you're analyzing only switchers, but often give flaky results in analog or device-level applications.

Since PSpice supports Mextram models, avalanching transistors, maybe I can figure out a ordinary Spice subcircuit match-up.

It would be useful to have a model properly model BVceo breakdown. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

Zetex have a few models, ZTX415, FMMT415, etc.that don't come anywhere near datasheet performance, in LTSpice, at any rate. They might go in PSpice, I dunno,

Convoluted designs involving "zener" models :-(

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

They work great. You can get a clean 25 kilowatt pulse out of a SOT-23. But don't expect a Spice model to be useful. Just try them.

Good project for Sloman.

John

I have those models... rather complex for a zener. What do they do in LTspice? ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

What does it do in the real world? In PSpice, I did a sweep of VCE, with floating base, and measured IC... breaks down/jumps up to about

700A at VCE=300V, then becomes resistive at about 40mOhms. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

.wine/On Wed, 04 Jan 2012 11:31:41 -0700, Jim Thompson wrote:

That's more or less what I see, using LTspice. I'm presently trying to reconcile performance with published figures.

Breakdown at Ib=0 thru 3mA is horrible - 700mA vertical step before it goes negative slope - down to D_D5 in the subcircuit. Breakdown at Ib>3mA looks more like the proper shape.

Simulated curve trace posted to a. b. s. e.

I haven't had chance to get some and look at the "real world" performance, yet, but I don't suppose they'll have that step.

As an exercise, I drew the subcircuit out. Here it is:

Version 4 SHEET 1 1348 680 WIRE 1040 -304 1040 -400 WIRE 1104 -304 1104 -400 WIRE 1184 -304 1184 -400 WIRE -288 -208 -432 -208 WIRE -192 -208 -288 -208 WIRE -112 -208 -192 -208 WIRE 400 -208 -112 -208 WIRE 480 -208 400 -208 WIRE 592 -208 480 -208 WIRE 704 -208 592 -208 WIRE 880 -208 704 -208 WIRE 1040 -208 1040 -224 WIRE 1040 -208 880 -208 WIRE 1344 -208 1040 -208 WIRE -192 -176 -192 -208 WIRE 592 -176 592 -208 WIRE -288 -160 -288 -208 WIRE -112 -160 -112 -208 WIRE 400 -144 400 -208 WIRE 480 -128 480 -208 WIRE 480 -128 448 -128 WIRE 464 -80 448 -80 WIRE -288 -48 -288 -96 WIRE 176 -48 -288 -48 WIRE 192 -48 176 -48 WIRE 208 -48 192 -48 WIRE 304 -48 288 -48 WIRE 400 -48 400 -64 WIRE 400 -48 304 -48 WIRE 592 -48 592 -96 WIRE -432 -32 -432 -208 WIRE 1184 -32 1184 -224 WIRE 1184 -32 768 -32 WIRE 464 -16 464 -80 WIRE 592 -16 592 -48 WIRE 592 -16 464 -16 WIRE -192 0 -192 -96 WIRE -112 0 -112 -96 WIRE -112 0 -192 0 WIRE -32 0 -112 0 WIRE -16 0 -32 0 WIRE 64 0 48 0 WIRE 80 0 64 0 WIRE 176 0 176 -48 WIRE 176 0 160 0 WIRE -192 16 -192 0 WIRE 1184 16 1184 -32 WIRE 768 32 768 -32 WIRE 1184 32 1184 16 WIRE 1280 32 1184 32 WIRE 704 48 704 -208 WIRE 720 48 704 48 WIRE 1184 48 1184 32 WIRE 1280 64 1280 32 WIRE -32 96 -32 0 WIRE 720 96 -32 96 WIRE 880 96 880 -208 WIRE 992 96 880 96 WIRE 1104 96 1104 -224 WIRE 1104 96 1072 96 WIRE 1120 96 1104 96 WIRE -192 112 -192 80 WIRE -192 144 -192 112 WIRE 768 144 768 112 WIRE 704 160 704 48 WIRE 1008 160 1008 144 WIRE 1008 160 704 160 WIRE 1184 176 1184 144 WIRE 1280 176 1280 128 WIRE 1280 176 1184 176 WIRE 768 192 768 144 WIRE -32 208 -32 96 WIRE 720 208 -32 208 WIRE 1184 208 1184 176 WIRE 1184 224 1184 208 WIRE 1280 224 1280 208 WIRE -432 240 -432 32 WIRE -400 240 -432 240 WIRE -192 240 -192 224 WIRE -192 240 -400 240 WIRE -432 256 -432 240 WIRE 704 256 704 160 WIRE 720 256 704 256 WIRE 592 272 592 -16 WIRE 768 272 592 272 WIRE 1344 304 1344 -208 WIRE 1344 304 1184 304 WIRE 704 368 704 256 WIRE 1056 368 1056 144 WIRE 1056 368 704 368 WIRE -432 384 -432 336 WIRE -432 416 -432 384 WIRE 1184 416 1184 384 WIRE 1184 416 -432 416 FLAG 1184 16 9 FLAG 1072 96 8 FLAG 1184 208 7 FLAG -432 240 5 FLAG -432 384 6 FLAG -192 112 4 FLAG 304 -48 12 FLAG 192 -48 3 FLAG -112 -208 10 FLAG -192 0 2 FLAG 592 -48 11 FLAG 768 144 13 FLAG 1184 -400 16 IOPIN 1184 -400 Out FLAG 1104 -400 15 IOPIN 1104 -400 In FLAG 1040 -400 14 IOPIN 1040 -400 BiDir FLAG -400 240 5 FLAG 64 0 1 SYMBOL npn 1120 48 R0 SYMATTR InstName Q_Q1 SYMATTR Value Qmod1 SYMBOL res -448 240 R0 SYMATTR InstName R_R1 SYMATTR Value 100 SYMBOL res -176 240 R180 WINDOW 0 36 76 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName R_R2 SYMATTR Value 100 SYMBOL res 304 -64 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R_R3 SYMATTR Value 100 SYMBOL res 176 -16 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R_R4 SYMATTR Value 500 SYMBOL res -208 -192 R0 SYMATTR InstName R_R5 SYMATTR Value 2k SYMBOL res 576 -192 R0 SYMATTR InstName R_R6 SYMATTR Value 2 SYMBOL diode -448 -32 R0 SYMATTR InstName D_D1 SYMATTR Value DZ20 SYMBOL diode -176 80 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D_D2 SYMATTR Value DZ500 SYMBOL diode -304 -160 R0 SYMATTR InstName D_D3 SYMATTR Value DZ200 SYMBOL diode 48 -16 R90 WINDOW 0 0 32 VBottom 2 WINDOW 3 32 32 VTop 2 SYMATTR InstName D_D4 SYMATTR Value DZ500 SYMBOL diode 1296 128 R180 WINDOW 0 24 64 Left 2 WINDOW 3 24 0 Left 2 SYMATTR InstName D_D5 SYMATTR Value DZ300 SYMBOL cap -128 -160 R0 SYMATTR InstName C_C1 SYMATTR Value 20p SYMBOL sw 768 288 M180 SYMATTR InstName S_S1 SYMATTR Value Smod1 SYMBOL sw 768 16 R0 SYMATTR InstName S_S2 SYMATTR Value Smod2 SYMBOL sw 1088 96 M270 SYMATTR InstName S_S3 SYMATTR Value Smod3 SYMBOL voltage 1184 208 R0 WINDOW 123 0 0 Left 2 WINDOW 39 24 106 Left 2 SYMATTR SpiceLine Rser=0 SYMATTR InstName V_H1 SYMATTR Value 0 SYMBOL h 1184 400 R180 WINDOW 0 24 96 Left 2 WINDOW 3 24 16 Left 2 SYMATTR InstName H1 SYMATTR Value V_H1 50 SYMBOL e 400 -48 R180 SYMATTR InstName E1 SYMATTR Value 10 SYMBOL ind 1168 -208 M180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L_L1 SYMATTR Value 1n SYMBOL ind 1088 -320 R0 SYMATTR InstName L_L2 SYMATTR Value 2n SYMBOL ind 1024 -208 M180 WINDOW 0 36 80 Left 2 WINDOW 3 36 40 Left 2 SYMATTR InstName L_L3 SYMATTR Value 2n TEXT -88 496 Left 2 !.MODEL Qmod1 NPN IS=3E-14 NF=1 BF=110 IKF=0.4\n+VAF=1900 ISE=1E-12 NE=1.6 NR=1 BR=7 IKR=0.2 VAR=75\n+ISC=1E-10 NC=1.9 RB=0.4 RE=0.1 RC=0.1 CJC=10.9E-12\n+MJC=0.347 VJC=0.476 CJE=82.6E-12 TF=1.3E-9 TR=2.3E-7\n.MODEL DZ20 D IS=1E-15 BV=20 IBV=100u\n.MODEL DZ200 D IS=1E-15 BV=200 IBV=100u\n.MODEL DZ300 D IS=1E-15 RS=0.1 BV=300 IBV=100u\n.MODEL DZ500 D IS=1E-15 N=10 BV=500 IBV=100u\n.MODEL Smod1 VSWITCH ROFF=1e10 RON=0.1 VOFF=4.3 VON=4.6\n.MODEL Smod2 VSWITCH ROFF=1e3 RON=1.0 VOFF=4.5 VON=9\n.MODEL Smod3 VSWITCH ROFF=1e10 RON=0.1 VOFF=20 VON=25 TEXT -80 464 Left 2 !.model ideal D (Ron=1n Roff=1T Vfwd=in)

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)