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Questions tagged [diodes]

Diodes are semiconductor components made from a P-type and N-type silicon material, that allows current to only flow in one direction.

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Chromebook power circuit: Surface mounted diode or resistor? [on hold]

I recently enjoyed finding out a mains power short (was working onsite project) has dislodged 2 surface mounted components from my device's motherboard. Thought it would be interesting to repair ( ...
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1answer
90 views

24vac to 24vdc with bridge rectifier BUT

I am needing to power a 24vdc gate motor, it is rated for 24vdc 1A on battery power and 24vdc 4.5A on mains power, i have a laptop charger(AC Adapter) that does 220vac to 24vac and 4.5A but i need the ...
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2answers
47 views

What should be the output resistance of this source with series diode?

Below shows three sources with open terminals: simulate this circuit – Schematic created using CircuitLab In Figure 1 if we want to calculate the output resistance, according to the linear ...
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2answers
40 views

Wha't the difference to use the junction to case thermal resistance instead of the junction to lead thermal resitance?

In case I have a diode, and I want to know it could dissipate the power, I have two values, but I can't choose between them: - Junction to ambient thermal resitance \$R_{ja}\$ - Junction to lead ...
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2answers
50 views

Row Column Matrix Problem with Flyback Diodes

So I had a simple row column matrix which I am driving with mosfets to power solenoid locks like this: GC is ground via 1.5k resistor C is 24V via 1.5k resistor And these are the connectors: ...
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2answers
938 views

Why is there a diode on the RX pin of the Adafruit Ultimate GPS board?

I can't seem to understand why there is a diode at the Rx pin on this Adafruit Ultimate GPS board. If we are sending data to the GPS, why put a diode that prevents current flow into this pin?
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1answer
54 views

Help identifying a diode

I am looking for some help identifying some diodes in the photos in the link below. They are being used in a hacked emergency call system. One of the diodes has some of the following nomenclature. ...
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0answers
13 views

Temperature dependence of pn junction characteristics

What is the difference between reverse saturation current and leakage current?Are both of them temperature dependent?
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2answers
65 views

How is voltage divided between two reverse-biased ideal diodes?

Suppose we have two identical ideal diodes (without any resistance or voltage drop). We connect these two diodes in series, in the same direction, and reverse-bias them with voltage V. Now we have two ...
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3answers
679 views

How do I figure which LED I need?

I need to replace two LED diodes on a TP4056 board (bottom right corner on the picture). The board is going to be in a box and I want to move diodes to the small holes in the box. There are two ...
0
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4answers
62 views

Multiple Buck Converters

I have multiple buck converters, model XL4005 (datasheet ), fed from a 12V battery source to several devices i.e. My motors (require 12V), Arduino (requires 5V) and Transmitter module (require 3.3V). ...
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2answers
61 views

Is it possible to build a simple circuit where one switch controls all bulbs but small switches control individual bulbs?

Putting aside the embarrassment of asking for a 'simple' solution, I will state in advance that I know I could do this with push-to-make switches and MOSFETs. What I am stuck on is whether I am ...
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0answers
43 views

hump on rectified signal and inconsistency on gate signal

Following is the image of my circuit, I am working at the moment. This is not my own circuit but I am trying to understand and work on it. Following is the signal I am getting at Gate2. What could ...
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1answer
43 views

Wide voltage range comparator (with zener diode)

i need to switch the transitor (Vce minimal) when input voltage (0 - 18V) is greater than 6.3V. To achieve sharp edge I use a zener diode D1. However, I also need a protect transistor base, so I use a ...
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2answers
75 views

Find cause of diode destruction from destroyed diode itself

Is it possible to find the cause of power diode destruction, ie. if it was destroyed through: reverse overvoltage spike (reverse breakdown and subsequent thermal destruction due to reverse ...
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2answers
89 views

Please can someone help with a zener diode [closed]

If the rule is with parallel circuits that the voltage is the same across all nodes eg: How does a zener diode regulate a voltage? After the current passes the Rs resistor and we calculate that ...
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4answers
45 views

Lithium ion battery charging problem [closed]

I am making a rechargeable led light My power source is mobile litium ion battery, (3.7)v 1800mah Whenever is use to chrge this battery with the mobile charger 5v... The diode in4007 connected to the ...
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2answers
86 views

Designing a circuit that opens when less than 12 volts are applied and closes when more than 12 are applied

I'm looking to build a circuit where current only flows when there is a potential difference across the entire circuit of more than 12 volts (+- 0.1 V). I also need there to be only a small amount of ...
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2answers
75 views

230vac / 5vdc power supply design

I am making my own basic bench power supply mainly for testing logic gate circuits, relays, flip flops etc, that I can move around to different locations. The circuit of the entire schematic will be ...
0
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1answer
69 views

Diode equation for BJT

For For a BJT why is the diode current Ic and not Ie? Ie = Ic + Ib The base current also passes through the B-e junction modelled diode
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1answer
15 views

ADS Simulation: Schematic to find input impedace

I'm following a paper, using ADS, to find the input impedance of a shunt Schottky diode. The paper's schematic is Fig. 1, and my schematic is Fig. 2. The point is that, I could not get the same result ...
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2answers
33 views

How dopes depletion region decrease in forward bias?

From what I understand is that, electrons from the N region diffuse into the holes in the P region. In doing so, they form a layer of positive and negative ions and thus an electric field. When a ...
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0answers
27 views

Zener diode equation proof (chacteristic curve)

I'm trying to prove this equation(at least I think that's the correct one): which produces this graph: I can prove the one that describes the PN diode but I am not sure what I should do differenly ...
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2answers
86 views

Direct FM generation using varactor diode

I am trying to generate a constant 1 MHz FM carrier wave. I have achieved it via LC parallel resonance circuit. Initially I let the switch B open and switch A closed, in order to charge the capacitor. ...
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1answer
63 views

Is there a variable forward voltage diode-like device or circuit construction?

I need to make a test PCB for an LED drive circuit that can drive a variety of different single LEDs. The forward voltage (Vf) of the LED could be anywhere from ~2.2V up to ~6.5V. I'd like the test ...
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0answers
58 views

PV cells (photovoltaic) I-V curve plot simulation

I am trying to plot the I-V curve using python because that helps me in understanding PV cells / solar panels (and diodes as a general thing). I know the formulas ...
2
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0answers
35 views

How to select a diode for baker clamp?

What are the requirements when selecting a diode for baker clamp circuit? 1- for example, How the reverse leaking current of the diode affects the circuit? can a diode with relatively high reverse ...
4
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4answers
518 views

Use audio frequency to light up multiple LEDs

Need some help here - I need to light up about 20 different LEDs based on the frequency input(200 Hz-20,000 Hz) Eg: The circuit should light up the 1'st LED when the input frequency is between ...
2
votes
1answer
68 views

Forward voltage tolerance on an ordinary diode

If one examines the datasheet of a diode such as the Vishay US1G, there is a graph of the typical voltage vs current such as Figure 3 below (with multiple lines for different temperatures): However, ...
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3answers
32 views

Half wave sine form factor example

Hint: in my calculations below, to make math easier, i assume that the diode = ideal(there is no 0.7 voltage drop across the diode) Vrms = 0.707Vp => Vp = 14.1v, therefore Vp(load) = 14.1v ...
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1answer
45 views

DC Motor Control with PWM and Polarity Switching

I want to be able to rotate the motor both clockwise and counter clockwise while also controlling the speed of rotation of said motor. This is a small dc motor and the whole thing is running on 5V the ...
2
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2answers
116 views

Two LEDs using, probable problem?

I use a simple circuit to notify user the reverse biased voltage to prevent some issues. Vcc can be -18~+18V, and two LEDs have exactly same reverse voltage (5V), but they have different forward ...
2
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1answer
62 views

Help Identifying a component for PCB repair

I'm helping a friend by attempting to repair this display PCB. It uses 24vac input and he accidentally hooked it up to 120vac. I am trying to identify the two components in this picture under the ...
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2answers
91 views

Is diode with forward voltage ~0.15v faulty?

I tested a diode model SB360 PFS which it showed about 0.15 forward voltage. The reverse voltage is zero. Looking the diode specification I read that Vf is 0.49v to 0.68v. So my question is if this ...
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0answers
40 views

Off load voltage in npn transistor as a switch

There is transistor tutorial on sparkfun.com (https://learn.sparkfun.com/tutorials/transistors/all). I am wondering why there is 1.3 V drop depicted across the LED1 on the picture, since when the base ...
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0answers
32 views

What are all the different diode current regions in the forward bias operation?

I know there is the usual drift-diffusion current, the Sah-Noyce-Schockley current and the Mott-Gurney high injection region; all these region governed by their own separate regions. I was wondering ...
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2answers
86 views

Diode forward voltage

Where does forward voltage of diode come from? I thought that forward voltage came from the transistor Vbe voltage (as far as I know, a diode is made of a transistor) : simulate this circuit – ...
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0answers
31 views

Forward bias diode

Can someone explain forward bias in a diode to me ? Here's what I understand up until. When we connect a diode in forward bias , holes and electrons are attracted to the depletion layer and they ...
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3answers
104 views

How to increase current capacity of an ideal diode circuit?

We know ideal diodes doesn't exist but there are circuits that behave similar to ideal diodes.So my question is. Can I add two ideal diode circuits in parallel each with 100 Amp current capacity to ...
2
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1answer
65 views

Noise generator with LM318

I want to build a noise generator from a Zener diode. I designed the above circuit. The noisy voltage from the diode is filtered via a high-pass filter and input into a 92x gain non-inverting ...
4
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2answers
821 views

Cathode to cathode diodes in schematics

I'm trying to understand the following circuits for an MPPT, and I do have some questions: Why there is a capacitor C6 in parallel with R2 for the voltage divider for analog reading, and how was the ...
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0answers
21 views

High voltage current source for TVS testing

I need to build a simple device for TVS diodes testing. For that test, I need to generate an 80V pulse (10 us width I think) with 1 mA current limit. The things that come up to my mind are current ...
2
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2answers
69 views

Trouble understanding this 'simple' circuit

I've been having trouble understanding this circuit, which is used in a larger circuit but this is the section which I can't wrap my head around. Valve7+ is always at +24V and when valve7 is high, ...
0
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2answers
103 views

How does this precision full wave rectifier work?

I am making a VU meter, and I need to rectify the audio signal for the IC comparator chip. I found this circuit in the datasheet, but I am unsure of how it works. I understand that the LF351 op amp ...
1
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0answers
31 views

Source voltage of circuit with diodes when output voltage is given

Tried solving this using KVL, and solving to get the currents for the different parts of the circuit, however got stuck when trying to compute the source voltage especially that I'm unsure if the ...
0
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2answers
85 views

Thevenins theorem + two diodes and a resistor using graphical solution

I've got a homework to solve this circuit by a thevenin's theorem and get a current and tension of the diodes using graph. I've looked all around the Internet and couldn't find one single video that ...
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7answers
180 views

Calculating the voltage drop of two Zener diodes in series? (reverse conducting)

I'm building a circuit powered from a 12V 55mAh (A23 battery). Needless to say that power consumption is a primary concern. The circuit is an ATtiny85 which is driving 13 LED's (in 5 groups). I ...
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0answers
23 views

Issues with calculating the minimum value of the Load Resistance (RL) in this scenario

I am currently in Year 12. I am facing issues with calculating the minimum value of RL before regulation stops in the following circuit: Below are the questions associated with this scenario: ...
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2answers
80 views

Very basic diode question

I was just thinking about diodes recently and I came across this video https://youtu.be/bXEyCf1P0UU?t=35 Minute 0:32 He says the power disspitated by the diode will be the forward voltage drop Vf (0....
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1answer
189 views

TVS bidirectional diode not working

10x bidirectional diodes 1.5KE400CA in series, balanced, then the chain in parallel for DC line protection. Breakdown voltage 400V per diode. Still got 10kV+ voltage spikes (picture below, x100000 ...