Questions tagged [npn]

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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72 views

NPN transistor switch wireless charger module

I am using this module for wireless charging, as a receiver, and i want to switch it on and off, because firstly it consumes about 5mA when idle and secondly i want to power it off when the battery is ...
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61 views

Transistor Input ON Voltage

I have this BCR116 NPN Transistor In the datasheet, they mention as Input ON Voltage instead of Base Emitter voltage like below : But my doubt is, when they say Input ON Voltage is 0.5V minimum, ...
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How can I make my voltage divider work?

I'm trying to read the voltage of the battery so I can simply calculate the battery status. I'm using a 8.4V battery (recharcable PP3) that I've meassured now to 5.57V. The circuit will die long ...
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73 views

High side switch sensitivity

I am trying to build some device that will emulate the operation of some module in my car. The input is the 12V logic signal from the trasmission control module. Basically, the device should take ...
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57 views

Current mirror collector voltage

I'm trying to get the VGS of DMHC4035PMOS. Based on the simulation, I'm supposed to get -5.53V but I'm getting -8.2V on my PCB. Is there anything wrong with the design? What is the collector voltage ...
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48 views

How can I find the power provided by the battery?

simulate this circuit – Schematic created using CircuitLab How can I find the power provided by the battery? I've calculated the operation point: Vce(Q1): 8.12V IC(Q1) = 1.63 mA Vec(Q2): 6.25V ...
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24 views

Microcontroller Vol Maximum Voltage compatibility

I am having this microcontroller - S32K142 64 pins - 5V Core voltage I have the below RESET signal connection which is provided by the MCU to the below transistor (which provides RESET to another ...
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50 views

NPN transistor as switch - does base resistor matter?

I'm a bit confused. I'm trying to use an NPN transistor as a switch to control a simple LED circuit. I assume that if I put it into active mode (emitter to ground, collector to Vcc), it just needs a ...
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46 views

Eliminate effect of VBE in NPN transistor to maintain same gain ratio for a low dc input signal and at all operating voltages

Good day, To monitor the current flowing through a varying resistor load across all supply voltages (8V to 20V DC), I am connecting in series, a small fixed sensing resistor and the drop across this ...
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Need help calculating resistors for a modular model particle accelerator

I foolishly took on a complicated school project of making a model particle accelerator. The idea was to make it a modular system, as in each segment, or "accelerator module" would be ...
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Very low voltage BJT behaivor

I'm interested in very low supply voltage boosting. 20-200mV, the lower the better. Usually such applications use zero threshold MOSFETs, but I'm curious if BJT will do the work too. In the datasheet,...
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2N3904, Power Supply & FuncGen results on strange output on the scope

I was having trouble with a Collpitts oscillator output, it was distorted, so wanted to check if I am indeed in the linear region of the transistor, so I decided to use the func gen to check that. ...
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72 views

Can a transistor send negative voltages when used as a switch?

I have used relays as a switch in order to turn on and off things. This is how I do it: My IC is my integrated circuit call it arduino. With a small current I am able to turn on and off things and I ...
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28 views

NPN BJT NOR gate to drive LED. Base resistance problem

Here's a circuit I'm trying to get working : I have two digital signals (B and C in the diagram) coming from a CD40174 flipflop. I use these to light up two LED's. I also use these as the input for ...
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79 views

Converting a NPN Circuit to PNP

I've got an exact circuit diagram of the circuit in NPN, but I need to convert it to PNP. Could someone help, please? I've got a 2N2907 with me right now and I want to make my High Level trigger into ...
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Half adder with soft latching input buttons

I'm trying to build a half adder with soft-latching buttons as input, using only transistors. I looked up online for some ideas and managed to build a soft-latching input circuit and a half adder ...
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168 views

Why it is preferred to use PNP and PMOS for pull-up, and use NPN and NMOS for pull-down

I have noticed that when I was designing universal logic gates like CMOS NOR gate that uses PMOS for pull-up and NMOS for pull-down. Then I faced it for second time with the H-bridge circuit, but ...
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44 views

Specific transistor for voltage regulating?

In 2SD1047 NPN transistor datasheet described the application for power supplies and the description is: The device is a NPN transistor manufactured using new BiT-LA (Bipolar transistor for ...
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1answer
56 views

BJT NPN Switch not fully turning off under certain conditions

My first post here, I'm relatively new to electronics and this is my first project that I'm trying to accomplish myself. First off, some background of what I'm trying to accomplish. I am trying to ...
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3answers
72 views

Why is the input to output delay time for transistors not provided in the datasheet?

I am using this BC807-40 transistor. My maximum collector current through the transistor is 200mA. I want to calculate the delay time between the transistor input Vbe and output Ic. Is there a way ...
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58 views

Latching circuit latches before pushing the latch button

I am a beginner and I am trying to build a latching circuit. In the diagram below, the LED is on while I expect it to be off. The push button should switch the PNP 2N3906 on, which in turn switches ...
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85 views

Anemometer with opamp

This is related to an earlier question of mine, but I have a different follow-up question that I wanted to make a new post for. I'm trying to understand more about how the below circuit works, ...
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Transistor operating region - push pull & current mirror

While looking at transistor based circuits, I am always trying to understand it with the transistor operating regions. Question 1: While looking at a push pull transistor based circuit, I want to ...
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Diode connected BJT instead of a diode

I have read wikipedia and other websites regarding the purpose of a diode connected BJT. But I am not clear on where should we use a diode connected BJT. My questions : Where is a diode connected ...
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63 views

Transistor - Saturation and Active Regions

I am using this BC817-40 transistor as a switch. In the above image, we can see that inorder to operate my transistor in the saturation region, I need to make sure my Ic/Ib ratio is less than 40. ...
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3answers
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Understanding a simple opto-isolator circuit

I have this circuit that is part of a schematic that I am trying to read. I have some idea, but I am not sure that I am correct. All I want is to figure out the D0 and D0_3V3 values. For example ...
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79 views

NPN transistor to drive a relay and IRF520 by ESP32 digital pin (3.3v)

I'm working on an automatic grow system that use sensors and actuators to keep cultivation in its optimal state, managing growth parameters dynamically. My first prototype was made with ESP8266 (...
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95 views

NPN SMT Transistor with flipped Emitter and Collector

Good day! I have designed a little circuit and got some (5) PCBs printed and assembled in china and unfortunately I made a mistake when I transferred my prototype circuit into my schematic. Even less ...
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35 views

Driving two 7-segment displays with a single shift register and BJT transistors

I'm building a circuit containing 8 switches representing 8 bits in a byte. I have two single digit 7 segment displays to display the two hexadecimal characters that represent the byte value. I'm ...
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4answers
333 views

Calculate output impedance of emitter follower

In AoE's chapter on BJT (specifically section 2.2.3B Input and Output Impedances of Emitter followers), it derives the input and output impedances to be: $$\mathbf{Z}_{in} = (\beta+1)\mathbf{Z}_{load}...
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Determine if a heatsink is required (Darlington TIP120)

I'm planning to switch 1A load at 5V with a TIP120. Looking at it's power derating graph I see that at 5W case can be around 140C, but how can I tell if it will get hotter than that? In the ...
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How to infer these parameter values from the datasheet for this transistor?

The circuit below depicts a continuous saturation state and uses 2N3904: From the above simulation the base current is 11mA, collector current is 14mA and the power is 11mW. I'm trying to compare ...
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Cut Off mode of an NPN transistor with PSPICE

]2 I am trying to model the cutoff mode of an NPN transistor with a switch that is connected to the base. Unfortunately, it shows current going through. I am using ORCAD Capture. Does anyone know ...
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NPN transistor in LTSpice

I just started learning NPN transistor and was trying to replicate Falstad - NPN sample in LTSpice. Somehow I get all base, collector and emitter current in the micro-Amp range while the sample shows ...
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How to amplify 3.3V to 10V by using an NPN transistor? How to select resistor based on current, how does the amplification happen?

I have basic knowledge about NPN transistors and I know how they work: for current gain based on the small input current in the base we are able to drive large amount of current in between collector ...
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157 views

Where does the 1V voltage come from?

I have a four PLC with many digital I/O connected similarly to the schematic below. If I use multi meter and measure the voltage between the two points in the schematic, why is it showing 1V? Isn't it ...
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3answers
250 views

2N2222 as a Switch

I'm pretty close to novice when it comes to tinkering with anything past a few resistors and LEDs, so while we're stuck in this fun thing called quarantine I figured I'd expand my knowledge. I ...
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2answers
184 views

ESP8266 not working to drive relay

I am trying to drive a 5V Relay using ESP8266-01 module. Following image is the circuit diagram i have uploaded. My sketch is about connecting the esp to the mentioned Access Point and controlling ...
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1answer
87 views

How to calculate Ic for a very simple NPN transistor circuit

I built a very simple circuit with an NPN (2N3904) transistor. Then, I swept Vce from 0 to 5V and plotted a Vce vs Ic graph (as shown in the picture). I heard Ic = Is*e^(Vbe/VT), where VT=0.025V, and ...
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58 views

Can't get 2N3904 transistor to allow the collector current I want, when used as a switch

I have a 3.7 V 18650 battery and I want to control a 3 V, 130 mA LED (high power CREE LED). I have calculated the series resistor for the LED (0.7 V/0.130 A) = 5 Ohms (ish) But when I apply any ...
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1answer
62 views

Make shed light come on, if dark outside and door is open (with NPN and hall-effect sensor) [closed]

I recently purchased a new shed with a polycarb roof. At night, when I enter the shed, I'd like a light that comes on (but not during the day!). I'm trying to find a way for the light to switch on, ...
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1answer
162 views

IC linear voltage regulator with NPN transistor

I want to build this circuit using an NPN transistor instead of PNP: I don't know what changes I must make to this circuit. I built the same circuit but using NPN transistors. The current was far ...
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1answer
82 views

Proper use of open collector to switch an output

I'm working with a pre-existing piece of consumer hardware that has an open collector GPIO output, as shown below: The Open Collector is able to source up to 100 mA. I'd like to switch a relay (a ...
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28 views

I can't reach the correct current with a BJT in LTSpice

The diagram above is what was given to me. I have to make: Vce = 1V Ib = 30uA I have two variable components, namely, Vcc (Voltage source from the collector), and Rin(supposed to be a ...
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88 views

Confusion about NPN base connection

I found an over-current protection schematic, but I am confused about how the base of the Q3 is wired. Is it connected to a potentiometer? If so, to what terminal?
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98 views

Linear regulator heats up at 60 volts

MY goal is to design a regulator which could receive (12 V to 60 volts DC as an input) and 5 volt with 60 to 70 mA current as an output. The reason I used three BJT's NPN (Q1, Q2, Q3), so I thought I ...
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40 views

Commute a 12 V siren with an ESP01

I would like to commute a 12V siren with an ESP01. I thought to use NPN or PNP transistors TO-92 that I have since a long time in my drawers. The ESP01 has 3.3V maximum at the output, and the siren ...
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2answers
59 views

Why does this BJT work as a switch in this logical-NOT circuit, no matter how I orient the emitter and collector?

I have built the following circuit (obtained from Electronics All-in-One For Dummies (For Dummies 2nd Edition)) It works quite well. When the the momentary button (normally open) is not pushed the ...
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How to protect my 555 timer against DC motor noise?

I have this circuit: (Sorry for such a bad schematic.) As you can see, there is a DC motor that gets power from 12V source, using a NPN transistor controlled by a 0-5V signal. Please note that ...
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1answer
95 views

How do I connect 24v NPN/PNP device to a Raspberry Pi GPIO without cooking the Pi?

As part of my "detecting the presence of an item on a conveyor" I'm looking at industrial through beam connectors. A lot of them are 3 wire NPN or PNP devices like this (highlighted): I'm wondering ...

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