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Questions tagged [npn]

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A type of bipolar transistor comprised of n-type semiconductor in contact with p-type semiconductor which in turn is in contact with a n-type semiconductor -> thus NPN. The transistor has three terminals, the Emitter, Base and the Collector. Current injected into the base controls the flow of current from Emitter to Collector enabling amplification and switching.

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I designed a Gilbert cell for analog multiplication, all the transistors (NPN) are in active region as I checked one by one, however, the result does not seem correct at all. How can I make it better? ...
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I have two different 12 V PNP & NPN proximity sensors. My first design was for each sensor type, having an identical PCB design with a normal optocoupler with a dedicated wiring arrangement. My ...
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I try to replace a sot 23 npn. The only markup is "NV" . It's used to switch a relay. I tested it with two transistor tester. Both of them show me a diode with the npn symbol. I dont know ...
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In my understanding, in an NPN junction for example, an increase in the emitter-collector voltage should widen the depletion layer in the base-collector junction therefore increasing the electric ...
Ilyes Ferchiou's user avatar
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I am trying to use transistor as switch and getting confused with the workings. For a NPN transistor, Collector needs to be connected to +ve and emmiter to -ve. If we look at the schematics below, in ...
Simsons's user avatar
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To understand the NPN current equation derivation, I have been studying my lecture handout and the emitter current equation accordingly is found as : \begin{equation} I_E= q n_i^2 A(\frac{D_p}{N_{dE}...
aziazu's user avatar
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Can somebody please explain in both cases the biasing method? I don't understand the following points: It's OK that we need ~0.7V for PNP and NPN base-emitter voltage, that's why a diode is used for ...
Darko's user avatar
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According to the circuit shown below: If we assume a Vbe of 0.7 V for Q1, the base current of Q1 is (5-0.7)/100 = 43 μA, and assuming a β of 100 for Q1, we have a collector current of around 4.3 mA. ...
Momo's user avatar
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I'm simulating turning an LED on with a transistor switch in LTSpice. To my bewilderment, the current through the LED in Circuit 1 is ~51 mA and the current through the same in Circuit 2 is only ~6 mA....
steelswords's user avatar
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I made a schematic in LTspice like in the first picture and then solved the question in second picture for Rb=100k. I have found Ib=0.03 mA, Ic=4.5 mA and Vce=-0.836 V but when I checked the graphic ...
Mando's user avatar
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I ran the schematic at the first picture but it gave five graphs like in the second picture. Is there a mistake?
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I am trying to get two disparate camera systems to talk to one another, specifically an Arri camera with a Preston system, and specifically to transmit a tally signal when the camera is recording. ...
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I made the schematic that is in the first picture and I wanted to plot Vcc vs. Vce but when I tried to plot, it gives an error like in the second picture. How can I fix the error?
Mando's user avatar
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I can't simulate the circuit in this picture. When I try to run it gives an error for missing I value. Could you help me? Could you tell me what Vce and Vbe are?
Mando's user avatar
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I'm trying to work my way through a pretty simple laser-based communication system (full description here) project I found online, just as a learning experience. I'm having issues understanding the ...
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I've seen many latching circuits through searching and reading some simple circuits. Most use NPN+PNP combination, some bistable ones use two NPNs, some use DPDT relays. Is the following circuit going ...
Elementronics's user avatar
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I am quite new to electronics. I am trying to control three LEDs with an Arduino using a transistor. I was wondering what the base current limiting resistor value should be. I looked around the ...
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I'm trying to build a simple circuit that allows a Raspberry Pi to detect AC voltage in a piece of wire inductively. I have the following circuit which basically uses an antenna wrapped around the ...
Dyverge's user avatar
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I have a circuit where many NPN BJTs are interfacing 3.3 V GPIOs with higher voltage circuitry. Each application has a similar setup to the image below (resistor R422 is what's in question). I did ...
Feynman137's user avatar
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While studying Grob's Basic Electronics chapter 28 I came across this statement, Notice in Fig. 28–2 that the EB depletion layer is narrower than the CB depletion layer. The reason for the different ...
Mohsin Raza's user avatar
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β = current gain I made the circuit of the above picture with LTspice. (A graph of Vce) (A graph of Vbe) And I was able to get 4.2966V for the value of Vce and 0.6543V for the value of Vbe. However, ...
user299980's user avatar
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In his answer to my question about common emitter amplifiers, @glen_geek commented that the RF receiver pre-amp I used as an example (shown in Figure 1) was "too simple" and that "any ...
kene02's user avatar
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I have the attached NPN transistor being switched by an MCU. I've made some measurements and done my calculations as a result of observing that the NPN is not fully switching off (the relay stays on). ...
RoyalAce's user avatar
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I constructed in multisim a common emitter circuit from the following diagram where the lower Keithley is used to supply VBE and the upper Keithley is used to supply VCE. I obtained the IC- VCE ...
Ture's user avatar
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I have an MCU (1.8 V logic levels) driving an NPN transistor to turn an relay on/off. The relay has a 12 V DC coil with resistance of 1028R per datasheet. This would require a current of 12/1028 = 11....
RoyalAce's user avatar
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I posted my original design yesterday and got many comments about my errors. This is revision 1 of my design. I am now pretty sure I have the load resistors calculated correctly, but still unsure ...
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I am new to electronics so I'm not too sure about how I should be calculating the base resistor to use in this circuit. I think the load resistor is calculated correctly (data sheet at bottom for ...
Zach Work's user avatar
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I want to turn a white LED on and off via my microcontroller GPIO. The ESP-01S board that I have uses an ESP8266 chip, which has a limit of 12 mA GPIO output current. However, I want to drive this LED ...
finefoot's user avatar
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According to this screen grab the Collector Base junction must be "reversed biased". I seem to be confused about the meaning of that. I thought that the Collector needed to be at a higher ...
khelms's user avatar
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I've come across a guitar pedal circuit called a "Tube Sound Overdrive". The schematic is shown below. It looks like a typical common emitter transistor circuit with an adjustable bias (RV1),...
Dave H.'s user avatar
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I'm trying to understand this circuit, but I'm having trouble understanding what the second op-amp block does. I understand tha the first one is an oscillator controlled by a trimpot (RL,) but the ...
Guilherme da Costa's user avatar
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I don't understand how we can model an NPN transistor with two diodes with their anodes connected. Shouldn't they be in series, with the base being in-between the diodes? An NPN transistor is in ...
khelms's user avatar
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I have inherited a tachometer signal conditioning circuit. It has an NPN transistor (2N3904) with a Schottky diode (BAT54) between the emitter and the base. It is preceded in the circuit by an LT1017 ...
Michael Nunan's user avatar
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I'm using the Raspberry Pi's GPIO to display some information in a LCD (using I2C) and to enable the usage of a few buttons to navigate through the LCD menus. There's another button, the one I'm ...
dan_soah's user avatar
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Consider this transistor. How do the voltages Vb, Vc and Ve vary as we increase ...
user200783's user avatar
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In my experience, an emitter-follower amplifier is usually AC-coupled to both its input and output: However, I recently came across such an amplifier which is DC-coupled - the capacitors C1 and C2 ...
user200783's user avatar
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I am trying to replace several transistors on my PCBs due to chip shortages. One such unit is a particular NPN transistor datasheet I cannot get my hands on these little guys anymore. But I figured ...
Feynman137's user avatar
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I understand that R1 and R2 make a voltage divider. initially Q1 is not conductive, so is Q2? initially C1 acts as short circuit, so flashes the light L1 for a moment? Please correct me if wrong. ...
Coppers Copernicus's user avatar
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I needed a generalized circuit that would switch on/off any device on the Vcc side with varying voltage (3.3 to 24 V) and current (0 to ~10 A). A P Channel MOSFET is an obvious choice, but I didn't ...
markwkiehl's user avatar
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I have what I thought was a simple relay circuit but the relay is always on. This is the part of the project that is not working Q5 never switches off. To simplify it further I removed the relay and ...
AndrewT's user avatar
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Does anyone know of a website or online tool to help identify a transistor-like component by its markings? For instance, one cracked and from the pieces, I can't be sure what it used to read (partial ...
Marcos's user avatar
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I want to build this FM transmitter that runs on 1.5-3V. I've got 2 questions so far: Can I use a 2N2222A NPN in this application? (I think I can but want to double check.) How can I calculate (or ...
GhostDog98's user avatar
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I'd like to use a P-channel MOSFET as a on/off switch. I can't pull the gate down directly from my controller because the voltage of the load is 12v, thus I have to use another transistor, as far as I ...
php_nub_qq's user avatar
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I am trying to choose a transistor to use in a current mirror to prevent thermal runaway of parallel LEDs (yes I have to connect them in parallel. I know connecting in series or using separate ...
MRB's user avatar
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Imagine we have an NPN transistor and the base voltage Vb = 0V. How can the transistor be in the cut-off region? I've started by assuming it to be in the active region and then calculated the emitter ...
AYUSH MEENA's user avatar
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I have an NPN tachometer sensor. I want to measure the rotation speed of a three phase motor, but the output frequency of the tachometer changes. For example, if the actual value of the motor ...
macrobert's user avatar
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I'm using this online calculator to get -50 gain for a cascode amplifier: https://www.daycounter.com/Calculators/Cascode/BJT-Cascode-Calculator.phtml However, I failed to duplicate the value in ...
Kira Yamato's user avatar
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Circuit simulation is here There are two parts to this circuit. The first part is a switch that is either floating or grounded, controlling a large number of relays via pnp transistors. (Many relays ...
cat pants's user avatar
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Looking at this circuit (first circuit): Choose a value for V2 between 0V and 10V. Then how could we know the IB, IC, IE, VB, VC, VE? Can we solve it by hand (by hand means the value IB, IC, IE, VB, ...
Dat's user avatar
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I am new to electronics. I am reading this book called Practical Electronics for Inventors. This is a portion about bipolar transistors from the book: There are two things I don't get from this: ...
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