Spice Diode Modeling of Forward Overshoot & Reverse Recovery

I posted this previously:

That's a 1N914 from the middle of a 50-ohm transmission line to ground. You can see the pulse drive level on the P400 display; that's the unloaded generator output voltage... divide by 2 for the 50 ohm load.

The diode is effectively driven by 25 ohms.

Generator rise time is about 1 ns.

In that last pic, you can see the diode holding up the falling edge of the pulse for a couple of ns until it runs out of stored charge.

I wouldn't expect various "1N914" parts to be super similar.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

What is the voltage step? That's not clear to me.

I know :-( Been down that path many times ;-) Had to one time ban the purchase of Motorola LM324's due to severe cross-over distortion not seen in other vendor's parts. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

     Thinking outside the box... producing elegant solutions.

It's half the numbers seen on the P400 display. VH is pulse Vhigh, VL is baseline Vlow. The VH is the unloaded pulse voltage, and the generator is 50 ohms.

genVH(50r)-------------+---------------50R scope | A 1N914 K | gnd

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

Thanks! ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

     Thinking outside the box... producing elegant solutions.

What's the mechanism for forward overshoot? All those electrons and holes are trying to decide between Uber and Lyft?

--
Tim Wescott 
Control systems, embedded software and circuit design 
I'm looking for work!  See my website if you're interested 
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Probably ;-}

Actually it _is_ diffusion as Phil points out.

However that doesn't mean it's not modelable with Spice... as he WRONGLY asserts. ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

     Thinking outside the box... producing elegant solutions.

Those graphs only show the resistive dimension of the impulses. There will be a varying capacitance associated won't there, which would change the shape of the impulse depending on the impedance that the diode sees...?

Clifford Heath.

The P400 and the attenuator+scope are both clean 50 ohm things. The diode is in the middle of a longish 50 ohm line, so it sees a very ohmic 25 ohms.

The diode itself has a C-V curve, of course. And a little inductance.

Someone with more patience than me could do a more extensive exploration of the 1N914 behavior.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Caught them napping.

We built a 2KV pulse generator that uses a silicon diode in Grehkov/DSRD mode.

We applied 48 volts in the forward direction, and waited for the diode to conduct. The current rose linearly to about 100 amps in maybe 80 ns, still at +48. Then we applied -400 through a small inductor. The diode reverse conducted, basically shorted, for 50 ns or so as the reverse current increased, then suddenly opened, when the stored charge was depleted. The voltage twanged to -1KV for 2 or 3 ns, and we doubled that with a transmission line.

The trick here is to forward bias the diode briefly, before the carriers drift all over the place and pollute the junction. The HP1430 sampler (a 12 GHz oscilloscope in 1965) used a similar trick: forward bias a step-recovery diode for a few ns to make the reverse snap faster.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Yes. But even repeating the experiment with 2pF, or 2pF+ some R parallel, would at least give some indication of the dynamic impedance.

Clifford Heath.

John,

Could you repeat the experiment at different risetimes?

The theory (and gut) says the peak drops and "unsharpens" at slower risetimes and eventually goes away...the rate at which it does this is a measure of charge storage.

Thanks! ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

     Thinking outside the box... producing elegant solutions.

All of my Motorola experiences have been bad. Small signal transistors in audio stuff I was building in the '70s. A problem just waiting to happen. Arcade video games in the '80s. Mostly TTL chips. Highest failure of all brands. Often a quick fix was to replace any Motorola chips in the troubled area. Their 555 timer was notorious for that. I found some poor bonding from the die lead to the output pins on some TO-3 devices in the power supply. This was on some high end military stuff. Their RF comm stuff quality was generally fairly decent.

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Their microprocessors were great. 6800, 6802, 6803, 68K.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Here is a first-pass model without a whole lot of data...

for various rise/fall times...

** Analysis setup ** .tran 200ns 200ns 0 10ps .STEP PARAM TRF LIST

• 100ps 1ns 10ns 20ns 50ns ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

     Thinking outside the box... producing elegant solutions.

That's not a model, it's a screenshot of some waveforms. As usual.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

You and Phil need to grow up and cut the crap... I'm not going to divulge what's in the model... unless you want to pay for a model >:-} I'll post an encrypted model as soon as I figure out how to get a DOS prompt in Win7 !@#$%^&* ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

     Thinking outside the box... producing elegant solutions.

On Mon, 30 Jan 2017 17:37:44 -0700, Jim Thompson wrote:

A first pass LTspice model:

Include everything that follows (except the sig) into a file named D1N4148_FO_RR.lib...

• LTspice Encrypted File

*

• This encrypted file has been supplied by a 3rd

• party vendor that does not wish to publicize

• the technology used to implement this library.

*

• Permission is granted to use this file for

• simulations but not to reverse engineer its

• contents.

* *********************************************************************************** **** SPICE MODELING by JIM THOMPSON,

***********************************************************************************

** Model is a first pass on modeling a 1N4148 diode forward overshoot ** based on limited datapoints ** Subcircuit Instantiation Node Order is: ** Anode Cathode ** Call as: Xyz Anode Cathode D1N4148_FO_RR *****

• Begin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

• End 2231672352 423449410

...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| STV, Queen Creek, AZ 85142    Skype: skypeanalog |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 

     Thinking outside the box... producing elegant solutions.

That's your prerogative of course.

But the disagreement could easily be avoided by not calling it a model in the first place.

If you're not going to share what you know, all you are doing is bragging about how smart you are, with no proof.

Encrypted model? Sounds paranoid to me.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com