Skip to main content

# Questions tagged [junction]

The tag has no usage guidance.

35 questions
Filter by
Sorted by
Tagged with
1 vote
0 answers
48 views

### Junction diode "built-in" voltages

When a PN Junction terminal are left open-circuited, the voltage measured between then is zero. The Junction voltage Vo does not appears. Because similar built in voltages arise at metal semiconductor ...
-1 votes
2 answers
71 views

### Why does the resistor need to be placed before the junction in an RTL NOT Circuit

I am trying to implement a simple inverter using transistors. I am confused why placing the resistor between the junction and the LED will not work, but placing the resistor before the junction does ...
6 votes
3 answers
313 views

### Why is collector current in a diode-connected transistor not subject to the non-ideality of the B-E junction that it must necessarily traverse?

In a recent comment I was asked why a diode-connected transistor behaves as it does. Jonk's answer here addresses this question, and explains that the geometry of the B-E junction in a signal BJT ...
• 38.8k
0 votes
1 answer
73 views

### Estimating GaN HEMT junction temperature

I think it's quite a simple question, but the solution is not so obvious for me. I know the equation Tj=Ptot×Rth+Ta, the thermal resistance Rthj-a and RDSon temperature dependance come from the ...
• 11
1 vote
6 answers
519 views

### No voltage gain in a common-emitter class A amplifier using a 3904 NPN transistor - Ngspice simulation

I am currently trying to build an amplifier for a condenser microphone in order to use it as a way to amplify an acoustic guitar. I am having some trouble to achieve my goals. In order to learn I ...
• 13
11 votes
3 answers
2k views

### What does the 'junction' of a silicon semiconductor look like in real-life?

The P-N junction is a small area within a package where heating is most prominent. Junction temperature is a key parameter we try to track when operating a diode or a transistor. I am wondering what ...
• 749
11 votes
3 answers
1k views

### Can SiC diodes run at higher temperature than common silicon diodes?

For a usual silicon semiconductor, the junction temperature is rated at 150 degree C. That said, for lifespan reasons, the usual limit for junction temperature is around 100 degree C. My question is ...
• 749
0 votes
1 answer
65 views

### Why in the output characteristic graph of BJTs, within the saturation region, is the collector current positive?

It is known that in the saturation region of the BJTs the pn junction is reverse biased. The reason for being reversed biased could be explained as follow: Vce=Vcb+Vbe Therefore Vcb=Vce-Vbe We can see ...
• 91
2 votes
1 answer
121 views

### Why aren't the majority charge carriers attracted by terminals of a battery when the p n junction is reverse biased?

It is clear that when the junction is reverse biased, the free electrons from the n side can not pass the depletion layer and fill the holes in the p side. But why will the free electrons not move ...
• 91
0 votes
1 answer
63 views

### Thermal design propagation calculations for a DCDC converter

So recently I've been doing some design for a DC/DC (this LMR33630) and now I'm doing the thermal design calculations using as a reference this Appnote, also from TI Accurate Thermal Calculations on ...
1 vote
1 answer
549 views

### Case temperature MOSFET

I am going to use a nMOSFET (NTMFS5C670NL) which will a varied power dissipation. The current going from drain to source is determined by a control signal. The maximum power dissipation for the MOSFET ...
1 vote
1 answer
110 views

### Majority Charge carriers and electron holes

Suppose I have an extrinsic semiconductor made of silicon and doped with phosphorous. Now, phosphorous has one more electron than silicon. After replacing one silicon atom, and taking its place, the ...
0 votes
1 answer
53 views

### Schottky barrier at equilibrium

At equilibrium, the barrier for electrons to go from metal to semiconductor is higher than the barrier for electrons to go from semiconductor to metal. Shouldn't that mean there are more electrons ...
• 447
1 vote
1 answer
420 views

### Why is the collector region doped?

As long as within the active region the collector-emitter junction is reverse biased, is there a purpose for which the collector must be doped? Moreover, not only that it is doped, but it is ...
• 113
1 vote
0 answers
85 views

### PN Junction Formation

When a PN junction is formed, free electrons from the N type diffuse into the P type material. Now books say that the same applies for holes, which diffuse from the P type material to the N type one. ...
4 votes
2 answers
142 views

### What prevents the lead attached to a semiconductor from forming Shottky junction

What prevents lead attached to a piece of semiconductor (for example in BJTs and FETs) from forming a Shottky junction?
• 111
1 vote
1 answer
210 views

### Blocking voltage of diodes

What exactly is blocking voltage in relation with Metal-semiconductor junction diodes? Is it related to breakdown voltage?
• 11
0 votes
2 answers
1k views

### MOSFET thermal resistance calculation

I went through the application notes of Infineon and TI. In the datasheet of the MOSFET a junction-to-case thermal resistance is given. Can we use these values to calculate the power dissipation in ...
1 vote
0 answers
340 views

### Calculate the Thermal Resistance (Junction to ambient) from Thermal Resistance (Junction to mounting base)

I have this MOSFET - MOSFET Datasheet I want to calculate the maximum junction temperature of the MOSFET part. I have calculated the power dissipation. In the MOSFET datasheet, there is only Thermal ...
0 votes
2 answers
635 views

### Thermal Resistance, PCB Operating Temperature and PCB Self Heating

I want to understand a few terms. My Questions : What does Maximum PCB operating Temperature for a PCB in general depend upon? Maximum PCB Operating temperature depends on Tg (Glass Transition ...
0 votes
1 answer
49 views

### 3-terminals magnetic tunnel junction

I was wondering if a 3 terminals magnetic tunnel junction can be implemented, as in the Figure. On the bottom I have a normal metal (NM), on the top a magnetic junction (FM = ferromagnet) and I can ...
0 votes
1 answer
1k views

### Thermal resistance Junction - Maximum Power dissipation

I want to understand the real meaning of the parameter 'Thermal Resistance Junction to Air (°C/W) to calculate the power dissipation. So for example if the value of this parameter is 250°C/W, should I ...
• 197
1 vote
3 answers
688 views

### Failed to plot junction capacitance versus reverse voltage in LTspice

The 1N4001 diode's junction capacitance versus reverse voltage plot is given as follows: I guess to measure this capacitance they applied 1MHz 50mV pk-pk sine wave signal as reverse biased and varied ...
• 12.2k
0 votes
4 answers
1k views

### 1N5822 schottky diode heatsinking

Is the cathode for schottky diode hotter than the anode, as is common for most diodes, or is it reverse polarity? A schottky is a metal-semiconductor junction, with the metal at the anode. So it ...
• 2,177
0 votes
1 answer
102 views

### Li-Ion Battery Charging Board Temprature (Junction Temp)

I'm looking for a little help with a simple battery charging project. I've bought a pack of cheap USB charging boards on ebay (link) with the intent of using one to charge a small Li-Ion battery. ...
0 votes
2 answers
7k views

### What does it mean bipolar or unipolar junction in a transistor?

I can't find the definition of unipolar and bipolar junction in a transistor, for example BJTs has a bipolar junction and MOS-FET has a unipolar junction, what does it mean unipolar and bipolar ...
3 votes
2 answers
253 views

### Evaluating junction temperature from thermal imaging data

I have a SOD-123F diode through which a current of ~1A flows, creating a forward voltage drop of around 300mV. The datasheet does not specify Rjc but gives Rja = 200 C/W and Rjl = 70 C/W for a 10cm x ...
• 192
0 votes
1 answer
848 views

### Collector-Emitter short but not Base-Emitter

I have a power amp that blew the pair of transistors(2SD1047 and 2SB817) at the output. The positive side 1047 is totally shorted, all junctions, the negative side 817 is only shorted Collector-...
1 vote
2 answers
221 views

### Relationship between junction area and voltage in forward biasing

What is the relationship between junction area and voltage in forward biasing? My book said that the voltage to establish forward biasing increases with decreasing of junction area. Why? EDIT: The ...
3 votes
1 answer
86 views

### Why can't current go through two voltage source junction?

I crossed out the middle because it felt like it wouldn't make sense. (Mostly because i felt like conservation of current was violated.) But im not sure why it wont go through at that particular ...
1 vote
2 answers
1k views

### Why don't the minority carriers combine with the majority carriers in a PN junction?

I wanted to start this question by giving my understanding of the make up of a PN junction. I do this so that you can pick me up on anything that I may be getting wrong in the lead up to my question. ...
1 vote
2 answers
503 views

### Is there any junction, or branch element for jumper cables?

I would like to create circuits using jumper cables. I have male-female, male-male, and female-female jumper cables too. But I cant find any branching cable on ebay. What should I use, to create ...
• 113
2 votes
1 answer
1k views

### Calculating maximum power dissipation based on contact area between two metal conductors

I am trying to figure out how to properly calculate the minimum contact surface area based on the maximum required power dissipation. Let me explain.. I am creating a custom semi-circular metal tab ...
• 83
0 votes
1 answer
159 views

### IC Thermal shutdown recovery time

Many RS485 transceiver chips have a thermal shutdown when the junction exceeds 150C. Typically they switch back on once the junction temperature drops 15 degrees. How long does that typically take? ...
• 245
10 votes
5 answers
4k views

### Where is the cold junction on the commercial thermocouples?

According to all textbooks and articles, a thermocouple must have a cold junction somewhere on the middle of it. But none of the commercial products have a middle point or a marked spot for ...
• 14.1k