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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Series resistor and Zener as overvoltage protection for ADC input

I am trying to come up with a simple overvoltage protection circuit for a Teensy's ADC inputs, which can only handle voltages between 0-3.3V. I am studying EE in college, but I haven't yet done much ...
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Ac voltage regulator to keep output voltage constant about 6v using diodes

I'm trying to design a circuit to keep the output voltage constant at 6 VDC for output load resistances between 0.5 to 3 kiloohm. It doesn't matter to have errors about 0.25 VDC on the output. My ...
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Select zener for minimal thermal drift

The voltage of a Zener diode in the Zener breakdown region depends on temperature. Suppose we have 3 Zeners with the following specs: 3.3 V rated Zener voltage at 5 mA 5.1 V rated Zener voltage at 5 ...
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6 votes
2 answers
363 views

Selecting series resistor for a Zener diode

I am currently designing a device that will be powered by eight AA disposable batteries. For reverse polarity protection I am looking to use a P-channel MOSFET in the following configuration: ...
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MOSFET gate-source protection, in selecting a Zener diode, is there any consequence of the forward voltage / current rating?

In a design, I have Zener diode used for the protection of a MOSFET's gate and source as shown in the picture below. I'm comparing two diodes for this purpose, and most of the spec values are equal, ...
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Is there an analytic expression for the avalanche and Zener diode VI curves?

Ordinary diodes obey the Shockley diode equation, but I can't find anything similar for avalanche and Zener diodes. It's easy to find their VI curves, crude piecewise fits and lots of descriptions of ...
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5 answers
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Can I use a normal diode as a Zener/Varistor ? If not, why not? (focus on Varistor use)

When I look at a normal diode graph like that I see the Vz Zener voltage of it looks just like a Zener, so why not using it reverse biased like a Zener? I ask like that because I never saw it being ...
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Zener diode Zener breakdown modelling

The IV curve of a Zener diode inside the Zener breakdown region looks like the IV curve of its forward bias operation. Is there a formula which can give the IV relationship in the Zener breakdown? The ...
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Glass Zener Diode Help

I'm not sure what type of zener diode this is. What I can tell is that it is either w15 or 315. I have 2 photos of the part in question. I have found that the one in question is shorted.
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36 views

Simple short, overvoltage and reverse polarity protection

I am looking for a simple way to protect the 3.3 V power supply to which the MCU and other peripherals are connected. The protection is supposed to be against short circuit, overvoltage and reverse ...
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How can I figure out Vout as a function of Vin?

I am not sure how to solve for when the diodes will be in what mode. Any help is appreciated :).
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3 answers
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Regulating voltage with a zener diode

I need to supply a comparator in a bipolar way, which admits bipolar voltages of up to +-18V, like the LM139 (open collector). In its datasheet it says that the High Level Output Current is 1uA and ...
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1 answer
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OVP with crowbar + TVS?

I'm looking to design an over voltage protection (for > 13-14V situations) on the input of a power supply (the PS is taking input from a 12V vehicle). I was considering only using a crowbar circuit ...
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2 votes
3 answers
200 views

Reverse polarity protection without Zener diode

I find the following reverse polarity protection circuit everywhere online. Reverse polarity protection using PMOS and Zener diode: Can you replace the Zener and resistor with a voltage divider as in ...
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1 vote
3 answers
263 views

Looking for solution to energize a relay ONLY when the alternator is running

I added a DC-DC converter in my truck so that I can charge the Lithium batteries in my RV. To turn on the converter, I am using a relay that ties to upfitter switches in my Ford F350 truck. This all ...
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Is there anything wrong with this SSR circuit?

I am a mechanical engineering student currently interning at a small company. We make solenoid valves and some tests require that we cycle the valves many times. This is a circuit that I came up with ...
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2 answers
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In the below application diagram, what is the point of having the transistor in series with a Zener diode?

This is a follow-up of an earlier question. Does it matter whether I drive the transistor T1 using Vout or Vz? (Keeping the other terminal open.) Don't the Vout and Vz potentials differ by just a ...
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Is there a mistake in datasheet connection?

In the application diagram shown below for LM723H, is the connection from Vout pin missing? Shouldn't be shorted to output? The internal block diagram is as follows: Iam assuming below is the ...
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What is the meaning of the following statement regarding Zener diode addition at the output of a voltage regulator?

What is the need for adding an external diode at the output of a series regulator? What role does it play in the application circuits shown in datasheet ? Following is an excerpt from the datasheet ...
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Decoding SPICE Model for onsemi SZ1SMB5939BT3G 30V Zener

I would like to model using the onsemi 1SMB5936BT3G (30V Zener Diode) SPICE model, but the SPICE model is not acting as I am expecting. Built-in LTspice Zeners clamp the kickback no problem but the ...
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When use Zener Diode and when use Voltage Regulator IC in regulating voltage?

This question maybe general question, but I have my own case like below. I'm planning to make solar cell phone charger. I found 1 solar cell with this specification as follows: ...
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-1 votes
3 answers
96 views

What will be the current flowing through the Zener diode in following circuit?

When Vbat = 18 V, the Zener diode will be operational. Below are two possible scenarios of gate control of the MOSFET. When V2 = 5 V, the MOSFET is OFF and the Zener diode is not biased. When V2 = ...
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1 answer
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SMPS Zener diode value in gate driver

I've got an industrial SMPS for a laboratory optical microscope that failed. When probing to measure for voltages I accidentally destroyed some components. In the attached image I hand traced the ...
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1 vote
3 answers
118 views

Zener diode - Design is not the same as experiment

My design : The experiment result: V_R1 = 1.2 V V_Zener = 2.8V What happened to my circuit?
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1 vote
1 answer
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Please help identify this SOT-23-3 device marked T22 or T2.2

This looks like any other SOT-23 device: But the markings are turning up little. Pin 1 (bottom-left) has something connected to pin 3 (top.) Pin 2 is N/C. So this seems like a zener, except there ...
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Voltage regulation, 5V +10% to 5V

I'm making an isolated communication/power module PCB, and I came across a problem that the B0505 isolated DC-DC converter has poor output regulation (+15% to -7.5% under load), and my HCS-LSP hall ...
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0 votes
3 answers
110 views

Using AC line as DC neutral reference for a microprocessor

I've been trying to repair this espresso machine circuit, but am scratching my head as to their use of the AC mains power seemingly as the DC reference. Any help would be appreciated. In total I have ...
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0 votes
1 answer
83 views

Does a Zener diode cut off immediately?

I want to turn off my micro-controller (Arduino) as soon as the battery reaches a specific low voltage. So, for example, if I have Zener diode with 9.1V Zener voltage, does that mean than as soon as ...
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3 answers
176 views

Multiple diode circuit homework problem

Can you show a step by step explanation as to how to find the current in each resistor? my attempt : I1 = (18V(input voltage ) - 7.5V(Zener voltage)) / 5k(resistance) I2 = (18V(input voltage ) - 24V(...
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3 votes
1 answer
320 views

Is this a correct way to divide and 'clamp' a noisy 10 V signal to 3.3 V?

I need to read a noisy 10 V Hall sensor square wave signal using an STM32 (3.3 V logic). To reduce the voltage I can use a simple resistor voltage divider, however, I'm not certain how to protect the ...
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5 votes
6 answers
938 views

I²C overvoltage protection fail

I have a pogo connector with +8.4 V/GND/SDA/SCL. I would like to protect my microcontroller from overvoltage (+8.4 V could potentially touch SDA/SCL). I tried this circuit: But the thing is: There is ...
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4 votes
2 answers
162 views

How to fix oscillation of an 'over-discharge protection' circuit for a lead acid battery

I've created a circuit to protect my lead acid battery from over-discharging. I used the following circuit diagram. Over-discharge protection circuit for a lead acid battery: For understandable ...
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3 votes
3 answers
359 views

Limit voltage follower output using Zener diode

I created a voltage follower/buffer for a first stage transimpedance amplifier and want to limit its maximum output voltage to roughly 3.3 V to protect the following ADC from voltage spikes. ...
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3 votes
3 answers
407 views

Zener diode and input voltage noise

I want to use a zener diode to clamp the input voltage. Input voltage is 12V with a +-4V noise. I want to know that if the noise in input voltage can affect zener voltage or not? If I have noise in ...
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7 votes
4 answers
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How to distinguish a 1N4148 diode from a Zener diode visually?

The 1N4148 looks like this and a Zener diode looks the same. What is the most recommended way to distinguish or identify them visually?
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-1 votes
2 answers
69 views

Graetz diode bridge with series LC circuit oscillation problem

I am trying to understand a problem I have encountered. I simulated the voltages on a Graetz diode bridge with a step voltage input of 24 volts. The schematic and the voltage signals are given below. ...
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2 votes
0 answers
97 views

Biasing a transistor with a Zener diode (calculate R)

I am trying to have a stable output voltage (12V) for the power supply that is changing between 28 V- 150V: simulate this circuit – Schematic created using CircuitLab I checked the datasheet of ...
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1 answer
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High-power LED Shunt Protection using Zener diodes with constant-current LED Driver

I'm about to build a custom high-power lamp. The lamp will operate a total of 60 high-power LEDs (operating point: 2800mA @3.1V per led) connected in series. The original plan was to have the LEDs ...
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5 votes
4 answers
152 views

"Sharp" transistor switching / minimizing fading effect

I'm trying to build a 9V battery tester with Zener diodes. I am doing tests with an adjustable power supply. With a 3904 transistor to do the switching it works ok, but the LED is fading on too slowly....
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9 votes
2 answers
2k views

Purpose of Zener diode in button

I’d like to understand if this is just iPhones or basically most of buttons have a Zener diode connected in parallel. What is the purpose of the Zener diode in the button here? What does it do in ...
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0 votes
3 answers
184 views

Zener diode in series with load

This may sound like a silly question, but what happens if we place a Zener diode in the reverse direction "in series" at the positive wire of the load without impedances other than the load ...
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3 votes
1 answer
196 views

Why do Zener diodes have a lower breakdown voltage than normal?

Here I do not understand some physics. So for normal diode we have a depletion zone width say Wn, and for Zener diode we have Wz. Then, we know that Wn > Wz. By reverse-biasing we make the ...
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2 answers
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MC33887: Zener diode on output avalanche protection

In the datasheet of the "MC33887 5.0 A H-bridge with load current feedback" there is a section on "Output avalanche protection", in which it is explained that an inductive flyback ...
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1 answer
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How to arrange input protection components?

I want to protect the input of my 5V micro-controller from two types of disasters, I am detecting a low on the input (0V): The input is from a switch. When the switch is on it provides a ground. Over-...
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2 votes
1 answer
246 views

Breakdown voltage in diode and Zener diode, what are the practical differences?

Until now, I've only studied with diodes asuming they are ideal and I could tell the difference between normal diodes and Zener diodes. Now, I started to study non-ideal diodes and I see that this non-...
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5 votes
3 answers
249 views

Zener diode as voltage limiter in a voltage divider?

Can I use a Zener diode to limit the output voltage of a voltage divider? I made a simple voltage divider (shown in the figure) that with 5V input gives me an output voltage of 3.3V. I Want to use ...
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0 votes
2 answers
169 views

Voltage divider plus Zener protection on op-amp input

I am designing a circuit to scale an input voltage to the range of an analog to digital converter pin on a microcontroller, and also provide electrical protection for the pin. I put together the ...
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7 votes
2 answers
770 views

FPGA over-voltage protection for input trigger signal

I don't have much experience with PCB design, but I am currently designing one to connect together several components for a work project. One of these components is connecting an external trigger ...
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0 votes
2 answers
53 views

How to calculate power requirement of Zener diode for specific frequency of operation?

I'm planing to control injector from MCU and this is schematics I came up with. Power supply voltage is 14V, inductance of L1 is 0.0014H, resistance of injector 16.6Ohm, and switching frequency is ...
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11 votes
2 answers
1k views

What is the point of the Zener diode in this schematic?

I looked at DALI application node and stumbled upon this circuit. Everything but the Zener diode D4 makes sense. What is the function of D4?
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