LTSpice zener diode 3V model

Thread Starter

hhsting

Joined Apr 25, 2024
167
cannot find any models for LTspice for Zener diode breakdown voltage of 3 V. I need Zener diode because I am trying to get simple voltage stabilizer and my load cannot handle more than 3 V. I cannot use voltage divider because many of these load and my power source supplies this and another 5 V DC load and 10 V DC loads. I do not want IC as I want to build my own voltage regulation. I also googled but didnt find any. Does anyone know where I can find model for LTspice?
 

ericgibbs

Joined Jan 29, 2010
19,115
hi hh,
A close match.
Insert this line in your standard.dio located in the cmp folder.
Adjust BV to suit

.MODEL GP3V0 D(IS=1E-11 RS=11.84 N=1.27 TT=5E-8 CJO=5.076E-10 VJ=0.75 M=0.33 BV=3.00 IBV=0.01 Vpk=3.9 mfg=Motorola type=zener)

E
 

Alec_t

Joined Sep 17, 2013
14,409
If you don't want to edit the standard.dio file you can get a reasonable 3V zener model thus :-
Place a diode symbol on your schematic.
Click 'Pick new diode'.
Click on an arbitrary low voltage zener diode.
Copy the highlighted text.
Paste it as a command on your schematic.
Edit the BV value to 3.0.

Bear in mind that a real-world 3V zener diode doesn't have a very sharp voltage knee.
 

Audioguru again

Joined Oct 21, 2019
6,783
Many 3.0V zener diodes have a tolerance of 5% (2.85V to 3.15V at their rated current and rated temperature).
There are a few 3V zener diode part numbers. Some are 3V when they have a current of only 50uA and others 5mA and others at 20mA. The voltage regulation is not perfect since the voltage changes when the load current changes.
 

Thread Starter

hhsting

Joined Apr 25, 2024
167
Many 3.0V zener diodes have a tolerance of 5% (2.85V to 3.15V at their rated current and rated temperature).
There are a few 3V zener diode part numbers. Some are 3V when they have a current of only 50uA and others 5mA and others at 20mA. The voltage regulation is not perfect since the voltage changes when the load current changes.
So what can one use besides ICs etc just basic components like resistor diodes leds etc to regulate voltage at 3V?
 

Thread Starter

hhsting

Joined Apr 25, 2024
167
Use the low-cost TL431 programmable Zener.
You can adjust it for a any voltage from 2.5V on up, and it's very stable.
That is not a diode thats shint regulators. I dont want to use that since I want to learn how to build my own shunt regulators using basic components like transistor, diodes, resistors and no ICs.
 
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Thread Starter

hhsting

Joined Apr 25, 2024
167
hi hh,
A close match.
Insert this line in your standard.dio located in the cmp folder.
Adjust BV to suit

.MODEL GP3V0 D(IS=1E-11 RS=11.84 N=1.27 TT=5E-8 CJO=5.076E-10 VJ=0.75 M=0.33 BV=3.00 IBV=0.01 Vpk=3.9 mfg=Motorola type=zener)

E
I did edit standard dio as shown above but its not showing up when i select pick diode??? What manufacturer zener diode and model name is that for real world application?
 
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BobTPH

Joined Jun 5, 2013
9,278
That is not a diode thats shint regulators. I dont want to use that since I want to learn how to build my own shunt regulators using basic components like transistor, diodes, resistors and no ICs.
A blue or white LED with a Vf it close to 3V could work. Use it forward biased where you would use a Zener reverse biased. It can also serve as a power on indicator!

Or put 4 or 5 regular diodes in series, again, forward biased.

How much current are we talking about? Anything more than a few 10’s of mA is probably not reasonable unless you use a transistor to increase the current.
 

Thread Starter

hhsting

Joined Apr 25, 2024
167
hi,
You have to Close LTSpice and then reopen LTSpice to register the change.
E

Test run.
View attachment 323201
I did many times. This time i restarted the computer and it is still not showing. I made changes to standard dio in my documents folder only. One in c drive program files LT and ltspicexiv doesnt let me change it.

what could the problem be? Why not showing up?
 

Thread Starter

hhsting

Joined Apr 25, 2024
167
A blue or white LED with a Vf it close to 3V could work. Use it forward biased where you would use a Zener reverse biased. It can also serve as a power on indicator!

Or put 4 or 5 regular diodes in series, again, forward biased.

How much current are we talking about? Anything more than a few 10’s of mA is probably not reasonable unless you use a transistor to increase the current.
My voltage supply varies from 5vdc to 12vdc. My liad uses max 3vdc . So i need something stable.

will blue led work vf to 3vdc with that varying supply? If not then what diodes work??
 
Look the datasheet of tl431 how a bandgap refference can be performed with transistors. But be ready for very hard study and matching transistors, another words you probably don’t get it.

Building a precise reference is a big topic. Once I reached 1% at 3V output (not a bangap type) and it was true challenge.

Most easy is supply a zener with constant current. You should reach about 2% accuracy at varying Vin voltage (5-12V), but not a temperature compensation:
 

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Thread Starter

hhsting

Joined Apr 25, 2024
167
Look the datasheet of tl431 how a bandgap refference can be performed with transistors. But be ready for very hard study and matching transistors, another words you probably don’t get it.

Building a precise reference is a big topic. Once I reached 1% at 3V output (not a bangap type) and it was true challenge.

Most easy is supply a zener with constant current. You should reach about 2% accuracy at varying Vin voltage (5-12V), but not a temperature compensation:
Can you please explain how your circuit works? What is difference between your circuit and just supplying zener diode with series resistance and take vout at zener diode? Also what model zener diode to use? Ant LTSpice zener diode model 3V?
 
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Zener voltage changes (let’s say 2.8-3.2V) because of current thru zener change. So if you supply a zener with relatively constant current the zener voltage will be more precise(3-3.1V).

Note: two diodes and transistor forms a 5mA current regulator, so zener is supplied always with about 5mA no matter what the Vin voltage is.
If you change 100ohm resistor to 47ohm the current thru zener will be 10mA. The 1k resistor for supplying two 1n4148 affects almost anything.

Suppling the zener with just resistor causes too much current change. Example, with 220ohm resistor and 3V zener, at 5V Vcc the current is 9mA and at 10V a 32mA.
 
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Thread Starter

hhsting

Joined Apr 25, 2024
167
Zener voltage changes (let’s say 2.8-3.2V) because of current thru zener change. So if you supply a zener with relatively constant current the zener voltage will be more precise(3-3.1V).

Note: two diodes and transistor forms a 5mA current regulator, so zener is supplied always with about 5mA no matter what the Vin voltage is.
If you change 100ohm resistor to 47ohm the current thru zener will be 10mA. The 1k resistor for supplying two 1n4148 affects almost anything.

Suppling the zener with just resistor causes too much current change. Example, with 220ohm resistor and 3V zener, at 5V Vcc the current is 9mA and at 10V a 32mA.
I dont understand how two diodes and transistor forms a 5mA current regulator, so zener is supplied always with about 5mA no matter what the Vin voltage is. If cange to 470 ohms its 10ma. can you go thru logic and calculation? How?
 
Voltage across 100ohm resistor is always 0.6V. So current thru 100ohms is 0.6/100=6mA. The same current flows thru zener.
If you change 100ohm to 47ohm the current will be 0.6/47=12mA.
So by picking this resistor you can set the current thru zener.
 
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