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Questions tagged [zener]

Zener is an effect in semiconductors, the name of a diode that uses that effect and more generally any diode that has similar characteristics to a Zener diode.

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Can I put schottky diodes in I2C line to prevent LTC2944 from powering my circuit through SDA and SCL?

I am using a LTC2944 connected to a battery that fluctuates between 11V and 14.4V. SDA and SCL lines go to a microcontroller and other peripherals (also connected to 3V3 via 10k resistors). I can read ...
Tomás Arturo Herrera Castro's user avatar
4 votes
1 answer
277 views

Zener instead of resistor divider on dc-dc converter feedback pin

This dc-dc converter steps up voltage from 3.1V to 7.5V. I'm curious about the unusual D2 zener + R3 resistor to set the output voltage, instead of the traditional resistor based voltage divider. I ...
Isacco's user avatar
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6 votes
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Will this over-voltage protection circuit work?

I am designing a PCBA that is powered from an AC adapter supplying + 19 VDC to the circuit. I want to add a protection against over-voltage, let's say up until + 24 VDC. I came up with the following ...
uz3il's user avatar
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2 votes
1 answer
512 views

Zener behaving strangely

I have recently put together a trivial low-voltage interlock circuit to prevent over-discharge of a 9v battery pack. I use a Potential divider of 1600 / 5600 ohm to produce 4.7v when Vcc is 7.2. I ...
mbdmbd's user avatar
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1 answer
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Identify Zener Diode with label of SF on an Antminer S21 hashboard

I have the following Zener Diode I need to replace, but I'm not sure how to identify it as there are 100s of diodes out there. The only marking I see is SF. How does one go about identifying this ...
Patoshi パトシ's user avatar
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1 answer
38 views

Jump on varistor I/V curve when "passing" through max. leakage current region to max. clamping voltage region?

I'm taking a course on semiconductor physics and another on something like "usage of electronic devices". On both I've come across the I/V curve on a varistor, this is: I cannot find the ...
Vito P.'s user avatar
4 votes
3 answers
317 views

Function of R6 in this voltage reference circuit

I've seen the following precision voltage reference circuit in schematic diagrams of several vintage instruments: I understand how this circuit works in general: it is basically two constant current ...
avian's user avatar
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2 answers
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Zener MOSFET Voltage Limiter

I need an input protection for a DC-DC converter in a 24V automotive system environment. The DC-DC is capable to accept 50V input but I need some sort of protection against load dump pulses which can ...
Emanuel's user avatar
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42 views

Current limit resistor calculation zener diode

I designed an overvoltage protection circuit. My input voltage is 90V, and I need overvoltage protection at 90V. However, I used a 91V zener diode in my circuit. I have a problem calculating the ...
Nitheesh's user avatar
3 votes
2 answers
323 views

How does a "regulating" source follower work?

Can someone explain to me how this circuit works? The output voltage is ~2.4V. The zener diode breakdown is 4.7V. From what I can see the OUT is simply Vgate - Vgs = 4.33V - 1.85V = 2.48V. Is this ...
JoeyB's user avatar
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4 votes
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Why do I get 9V while the figure in the datasheet says I should get ~4V?

How do I get ~4V from Figure 9.1 below, when I simulate it I get around 9V. Am I doing something wrong? The source of the original schematic "Figure 9-1" below is the Texas Instruments ...
JoeyB's user avatar
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Am I using the Zener Diode Correctly?

I am building a custom atmeta328 board that I want to make sure handles the bootloader properly. I have DTR from my FTDI chip going through a .1uF capacitor to the Reset pin on the MCU. I also have ...
Kevin McQuown's user avatar
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0 answers
57 views

Solid state relay switch circuit with Omron G3MB-202P

could somebody explain the use of the Zener diode and capacitor in the schematic of a switch utilizing an Omron G3MB-202P?
user3788160's user avatar
1 vote
1 answer
79 views

Understanding this constant power laser driver circuit

I am trying to reverse engineer a constant power laser driver. Unlike constant current drivers, these use an integrated photodiode which monitors the laser diode output. The photodiode current feeds ...
selene flemming's user avatar
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3 answers
71 views

Calculate resistor value in Zener clipper circuit

I'm trying to build a circuit which drives one of two LEDs from a variable voltage power supply, which can range between -15 to +15 volts. I'd like the LED to hit maximum brightness as early as ...
Ade's user avatar
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1 answer
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What is the quiescent current in a current limiting voltage regulator circuit?

Is the quiescent current simply the current drawn by Q1 and Rin when no load is connected to the output? How would this differ from the supply current?
user998479's user avatar
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2 answers
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Why is this Zener across the collector and emitter of this transistor driving a solenoid coil?

I am trying to understand a vintage (1970s) impact printer circuit. Each of the pins in the printer are driven by a small individual coil driver circuit, that was originally specified to look like ...
BZo's user avatar
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3 votes
2 answers
706 views

Why is this zener in series at the base of transistor, and has something failed?

I am debugging an ancient little impact printer and in my probing have found an unexpected voltage level. I'd like to understand this part of the circuit, why it's constructed as it is, and whether ...
BZo's user avatar
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1 vote
0 answers
26 views

Arrangement of isolated variable DC input

I design isolated DC input for industrial applications that can possibly work from 12 to 24 V. I add a 5.1 V Zener for over-voltage protection, a capacitor for filtering, and TVS for surge production. ...
Hamid s k's user avatar
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2 votes
1 answer
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Art of Electronics - Confused about Zener Diode voltage formula

Working through Art of Electronics and the section on Zener diodes confuses me. There's another question about this section on the site (Art of Electronics - Zener Diode Example), but I'm still ...
Clueless's user avatar
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1 answer
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Help Find Unknown Bad Zener: Digital Volt Amp Meter

This is Digital Volt Amp meter display module. Working voltage was max 30v and I burned the transistor BL P11 NPN (1A) with more input. Replaced with CXT5551 (600mA), operating current for module is ...
Paul's user avatar
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6 votes
2 answers
631 views

BJT B-E Zenering: whither the collector?

So, I'm trying to analyze how the circuit in this question behaves when subject to reverse battery (vs. being driven from OUT to IN), and I'm running into a severe snag in the process, though. It ...
ThreePhaseEel's user avatar
1 vote
3 answers
94 views

Zener Diode Current Explanation

What is the point of Zener Diode Current? I have to replace this BZT52C8V2-7 Zener Diode with the current version BZT52C8V2-7-F and the Zener Current is 700 nA vs the previous 5mA. What effects would ...
Wes Ellgass's user avatar
1 vote
2 answers
70 views

Can you identify this Zener diode?

I am looking for the part number of this Zener. I can't find the AA marking code on st.com.
Paolo's user avatar
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0 answers
34 views

Is it possible to design an over/under AC voltage protection circuit using only diodes and SCRs?

Is it possible to design a circuit using only SCRs and diodes (Zener or otherwise) as a main regulating device to protect a load (220 V, 80 W) from over- and undervoltage? Other passive components (...
Yeal Takian's user avatar
0 votes
1 answer
78 views

Negative Voltage Cutoff

How do I turn off a negative voltage supply using a Zener diode as well as transistors and resistors? Let's say I have -30V supply, but I wanted it to turn off at -15V (using the zener voltage as a ...
HuracanWind's user avatar
0 votes
2 answers
201 views

Zener diode as a switch

I would like to use a Zener and a NPN transistor as a voltage switch to close a 12 VDC relay. My thought was 12 V zener to the base to turn on the transistor and close the relay when supply is above ...
Daniel Hart's user avatar
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2 answers
240 views

Switch a transistor with a Zener diode

I have a source (J1) that varies from 2.0 V to 8.0 V. I'm trying to switch on a NPN transistor (Q2) when the source is above 5.1 V such that it can supply a control line (J3) via a PNP transistor (Q1)....
bluscape's user avatar
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0 answers
50 views

DC Bias network for a LCR meter

I am trying to make a DC bias network for my LCR meter (Scientific SM6023) based on this circuit I found online RD10E has a Zener voltage of about 10V and 1N4004 has a forward voltage of 1V. I have ...
amogh waghmare's user avatar
1 vote
1 answer
133 views

Zener diode on NRST pin of STM32

I am using STM32L476QGI6 in my project. As shown in the following figure, I have placed a 3.6 V Zener diode (ZM4729A-GS08) on the NRST pin of my microcontroller. The problem is that when I connect the ...
Hamid Saneie's user avatar
3 votes
3 answers
135 views

Vbe limit in basic series voltage regulator circuit

An ubiquitous series regulator circuit below sometimes used without any capacitors, but more often has a capacitor on the output as well as one on zener. simulate this circuit – Schematic ...
Maple's user avatar
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0 votes
3 answers
75 views

Voltage Regulation Techniques and BJT Usage in LT4363

There are instances when the input voltage is utilized to power a chip, and the maximum voltage (VCC) allowed on the chip is lower than the input voltage. In such cases, I consistently use a Zener ...
chami's user avatar
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5 votes
2 answers
692 views

What is the maximum frequency for a diode if a superimposed AC sine wave on DC pass through it, and the diode stays always ON due to DC?

How can I determine if a forward biased diode (always ON) can be used to pass the full band of a superimposed AC sine wave on DC? The diode is just used as a protection device against possible reverse ...
Gianluca G's user avatar
3 votes
2 answers
1k views

Zener diode equivalent circuit

When a diode is forward biased it has a voltage drop of 0.7/0.3 volts across it because of the depletion region. Therefore the equivalent circuit of the diode is represented as a battery and a bulk ...
Alex's user avatar
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0 votes
1 answer
77 views

Zener diode - What voltage at the anode at breakdown?

I'm designing a circuit where there is an analog switch that turns a load on. I specifically need the load to turn on only when the voltage is above a certain level. The analog switch takes VCC and ...
Felix Jen's user avatar
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3 votes
2 answers
189 views

Can I replace resistor and zener with voltage reference in basic serial regulator?

The title basically says it all. I wonder if I can use voltage reference like MAX6043 with NPN BJT to get a simple two-component power source? For the context, I have a circuit that should draw very ...
Maple's user avatar
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1 vote
1 answer
85 views

DC-DC converter possible by using Zener breakdown as input to transistor gate?

Suppose you have a DC voltage source that is higher than required, in this example let's assume one wants a 12V voltage source from a 18V source. Would it be possible to have a circuit, where the ...
luksen's user avatar
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0 votes
3 answers
199 views

Eliminating Negative Voltage Pulses (≤ 840 mV)

I have obtained a voltage signal from a Weigand sensor (a sensor that creates a low voltage signal when placed in a rotating alternate magnetic field), which generates a positive pulse of 1.2 V and ...
Taimoor Malik's user avatar
0 votes
1 answer
120 views

LTspice simulation

The Zener diode is an LM385-BZ 2.5. I could not find that SPICE model, so the circuit is running on standard values. The first picture below with Vout = 0-3.3 V is what I am trying to get, but the ...
luffy's user avatar
  • 1
0 votes
1 answer
74 views

Voltage regulator circuit calculations (zener diodes, transistors)

The circuit given in the following Figure is a voltage regulator which is used to supply a constant voltage. It has the following properties: Vin = 20V, Rs = 1 kΩ, R1 = 200 Ω, R2 = 800 Ω, R3 = 2 KΩ, ...
NonComposMentis's user avatar
2 votes
2 answers
634 views

µA723 output Zener diode: why is it as high as 6.2 V?

The µA723 voltage regulator has a 6.2 V Zener diode on its output. I am trying to understand why the Zener voltage is as high as 6.2 V. (LM723 or LM723C are more or less equivalent parts, raising ...
Tony's user avatar
  • 168
0 votes
2 answers
83 views

Current into DC/DC or LDO doubt

I need a circuit that regulate and invert the input signal 0-24V to 0-3.3V of output signal. Also a pullup that produce a low signal when the input is detached. I thought about a schematic like this. ...
Gigapel's user avatar
  • 61
1 vote
1 answer
142 views

How to bypass simple zener diode voltage regulation at low volts?

Is there a simple circuit to automatically bypass zener diode regulation at a voltage lower than its rating? I have a bunch of simple circuit designs that accept 11-15VDC but in the intended industry ...
Ken's user avatar
  • 33
2 votes
2 answers
308 views

What is the purpose of the Zener diode in this voltage smoothing circuit?

I was watching this video and he was explaining that this part of the circuit was to smooth out the voltage to make it stable enough to drive the MOSFETs. Just looking at it, I see it's just an RC low ...
Arthur Prudius's user avatar
0 votes
1 answer
123 views

Self-powered measurement unit for current transformer

A few days ago my friend told me his end-year project about a current transformer that capable of measure current with its own instrumentation. And some concept that we discussed confused me. Let's ...
enis's user avatar
  • 73
0 votes
3 answers
175 views

Use supercapacitor to power microcontroller

simulate this circuit – Schematic created using CircuitLab I try to solar charge a supercapacitor C1. When it's fully charged, I use a Zener diode D2 to the gate of an logic MOSFET M1, which ...
KungPhoo's user avatar
  • 101
1 vote
3 answers
322 views

Why design a clamper circuit with battery in series with a resistor?

I have been trying to design a circuit that clamps the positive peaks of an ac signal to +6 V. We can use batteries, resistors, and capacitors of any value desired in addition to Zener or conventional ...
RK Eshat's user avatar
  • 153
4 votes
3 answers
548 views

Downside/tradeoffs to clamping signals with zener diodes

I have a signal source that sends fast pulsing square waves in the MHz range (encoder pulses from a motor) down a long transmission line to a receiver. I have tried many solutions and different types ...
petemoss0's user avatar
0 votes
2 answers
176 views

Low Voltage Zero-Cross Circuit

I'm trying to read the wind speed with my Raspberry Pi. I have an anemometer that produces between 80mV and 12V AC at 0 to 125Hz (it's basically a wind turbine). I have it hooked up to an Analog-to-...
mgrocketman's user avatar
1 vote
3 answers
101 views

Generating TTL-level signal from an analog fast pulsed high-voltage DC signal

I am exploring feasible ways to design a circuit to generate TTL-level digital signal from an analog pulsed DC voltage output. The voltage range of the pulsed DC signal can be from 0 V to 3 kilovolts ...
Allison's user avatar
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