Episode #125 of the Stack Overflow podcast is here. We talk Tilde Club and mechanical keyboards. Listen now

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.

Filter by
Sorted by
Tagged with
0
votes
1answer
58 views

BJT Low Current Consumption Amplifier

I'm trying to amplify a 20mV ptp signal to something around 1V ptp. I intent on only doing this in one stage and require the amplifier to be very low power consumption (3.3V supply max 1mA for entire ...
1
vote
2answers
65 views

Voltage at Collector of NPN less than Minimum allowed for High

I have connected the collector of a NPN BJT (DTC144EE) to the Power_ON pin of my lte module (HL7588). The pin is internally pulled up by a 100k resistor to 1.8V. The module is powered on by driving ...
1
vote
0answers
46 views

Simulation of an Electric Shock Box

This is the continuity of this: Understanding Electric Shock Box Circuit I really don't understand what is going on, so I was hoping that simulating the circuit in Proteus might help What parameters ...
0
votes
1answer
79 views

BJT Circuit Current

I have a question regarding the circuit below. I am unsure how to calculate the current flowing through the 1k resistor. I think it is reasonable assumption that the collector of the PNP BJT must ...
0
votes
1answer
132 views

NPN common emitter transistor as a switch switches off as the current draw in collector falls

I am trying to switch power to a Pi Zero using an NPN transistor (2N2222) as a switch, as in the following diagram. simulate this circuit – Schematic created using CircuitLab The Ib is around ...
0
votes
1answer
49 views

How to determine transistor specification range for voltage and current (in relation to design requirements)

Attached is my current circuit for using a 5V logic output device to control 24V going to a load with max current draw of 14mA. (Ignore the name for transistor Q1, that is just a random NPN BJT). ...
1
vote
4answers
74 views

Current booster for relay

I have a DC power source which can provide up to 5V, 50mA (LabJack maximum output current, voltage bus-powered) and I want to power my relay (SDT-S-105LMR2,000) with 5V, 100mA. I have an option to use ...
1
vote
1answer
80 views

Driving NPN with Raspberry Pi

When driving an NPN transistor using the GPIO output on a raspberry pi I assume no protection is needed on the GPIO side of the circuit? So nothing would really be needed beyond this to drive the ...
0
votes
1answer
55 views

Do transistors naturally have resistance on base, collector, and emitter?

I'm using a circuit simulation app called EveryCircuit, and for the npn transistor settings it has forward beta, reverse beta, base resistance, collector resistance, and emitter resistance. I'm a bit ...
1
vote
3answers
39 views

Fundamentals of Output Characteristics of a BJT, what is the difference between load line and output characteristics?

In any transistor, we plot the output characteristics, i.e. effect of change in Vce on Ic. Next, we write the KVL equation on the transistor, i.e. Vcc = IcRc + Vce and plot the load line from this ...
3
votes
1answer
67 views

What are the functions of these components in this 15V 500mA power supply?

Hello guys, I want to know what is purpose of the transistor T3 (BC547B) in this circuit. I understand it provides base current to the series pass transistor T5 (2N3055). Also I want to know: What is ...
0
votes
0answers
45 views

BJT Latching Circuit Help

I have build a latching circuit using both a NPN & PNP BJT to turn on and off an LED, as shown below: simulate this circuit – Schematic created using CircuitLab When I built the circuit ...
0
votes
0answers
30 views

Calculating Nmax in loaded bipolar junction transistor inverter

I have tried various methods for calculating N max here, and some have resulted in negative answers while others have resulted in an answer of around 1. Is my method correct? Or am I missing ...
0
votes
2answers
72 views

Bipolar Transistor Inverter Circuit Analysis

I have been trying to understand this question and I'm just not sure what equation to use for the collector current. I'm not sure if I need to be using an output voltage function of time? All I have ...
0
votes
2answers
78 views

Why is current flowing mostly through the base (NPN transistor)

I am currently working to install an NPN photoelectric sensor (retro-reflective dark on: https://www.automationdirect.com/adc/shopping/catalog/sensors_-z-_encoders/photoelectric_sensors/18mm_round_-...
5
votes
2answers
797 views

Basic transistor circuit

I'm playing around with a BD179 transistor, trying to get my LED bulb to light up but without luck. My mistake is probably something very simple but I'm learning so bear with me.
1
vote
2answers
132 views

TL431 / TLV431 supercapacitor voltage clamping circuit

I have a question regarding a circuit I've been working on for some time. The circuit is based around existing supercapacitor protection modules and uses a TL431 (actually a TLV431 lower power ...
0
votes
1answer
81 views

Activating Relay Coil (NPN and MCU)

Circuit primitive in CircuitJS First, I'm having a hard time with transistors, and only recently managed to pass current through a NPN as planned (70-ish mA from 5 V with a 325 hFE 2N3904 with a 10K ...
2
votes
2answers
134 views

NPN Transistors Not Working When Emitter Is Grounded

I'm trying out transistor logic for the first time using PN2222 transistors that came in a kit that I got from Amazon. I've been running into some problems with making a basic NOT Gate (as shown in ...
-1
votes
1answer
80 views

Can I use 13003 transistor in place of 2n2222?

I am working on a project which requires a npn 2n2222a transistor as recommandation. But as of now the transistor is not available to me. Alternatively I have transistor 13003 and c945 available as ...
0
votes
2answers
116 views

Correct way to control 12V relay from a Raspberry Pi

I am working on a project where I need to control a couple of relays from the GPIO header on a Raspberry Pi. I tried getting a PCB with the layout like the right version in the image below, but I ...
-2
votes
1answer
89 views

How many NPN common emitter transistor circuits are there? [closed]

I'm studying for an important exam, solved a lot of common emitter circuits with different unknowns. Most of them them look similar. Can someone give me some examples or exercises of circuits of NPN ...
0
votes
1answer
88 views

Delay circuit with capacitor and transistor doesn't work as expected

I made the following delay circuit. According to the simulation, it should take in the order of seconds for the relay to switch. Instead what I find (even by varying the resistance of the second stage)...
1
vote
2answers
75 views

Modify DPDT push button with an NPN to control with GPIO?

I have an 2-port HDMI switch that swaps inputs using a 6-pin DPDT latching push button. I want to modify it to be controlled by a GPIO pin on my Pi rather than having to push the button. One way that ...
1
vote
1answer
75 views

How can I prove that Vce saturation lies below .2V?

When I try to prove that Vce for saturation is below .2V and I take npn transistor I simply consider emitter to be at 0V and thus base emitter junction being forward biased base gets a voltage of (.7 ...
0
votes
1answer
44 views

NMOS to NPN Circuit Analysis

I am attempting to us a voltage shut off switch with some pre-existing hardware. I do not understand transistors well enough yet and am looking for clarification. I desire for V2 to be able to go to ...
0
votes
1answer
60 views

Use of D3 and D5 in inverting circuit

I have simulated this circuit in Spice and it works as it is supposed to, but I fail to understand the use of diodes D3 and D5. I know it has something to do with T2 transistor. Edit: Correction ...
1
vote
2answers
83 views

How to derive formula for emitter current flowing through Re?

Ie = Ve/Re I was thinking about using that approach but i have been doubting myself if that is the right approach to go with, because then i have to express the emitter current in term of alpha and ...
4
votes
1answer
246 views

Understanding a PNP/NPN LED schematic

I bought and soldered a dirt-cheap flashlight kit from China. I'd like to understand how it works, though - specifically, why it uses a combination of a PNP and an NPN transistor (schematic from the ...
1
vote
2answers
54 views

Switching circuit transistor NPN, load has voltage and current though transistor is off

I am confused about the switching of this circuit. I can control the V1 input line. Output line is R4 load line. My Vbase (V1) is 0V, and Vbe is 0V. Transistor is off and collector should see 0V. That ...
-1
votes
1answer
31 views

electrons of the collector in NPN transistor

What happens to the electrons in the N region of the collector of npn transistor that operates in active mode ? I know that electrons coming from emitter split to base current and collector current ,...
-3
votes
1answer
75 views

Working region of NPN BJT

I have come across the following circuit where a BJT works as switch when I apply 23 volts to base using a 100k resistor. A 3.2 mA constant current source is connected to the collector of the BJT ...
6
votes
4answers
794 views

TIP120 Transistor + Solenoid Failing Randomly

I am using TIP120 transistors (controlled by 74HC595 shift registers) to control 12VDC, normally closed solenoid valves. Everything is working in short-time tests however when left overnight, some ...
3
votes
1answer
210 views

555 IC - Transistor Tester

Why are Pins 7 and 5 floating for this 555 IC and how does an NPN and PNP transistor when connected to E B C act a switch? Without the use of Pin 7 surely the capacitor cannot discharge which would ...
0
votes
0answers
28 views

Selectable sink or source Input

I'm looking for a circuit that I can add to a universal Input board that will be able to handle a 5-24v input PNP or an NPN 0v signal that I can connect to my arduino. I was considering using an ...
0
votes
1answer
39 views

How to activate a solenoid using TSOP4838 IR receiver

I have a TSOP4838 whose output is 5v normally and 2.5v when I press a button on my DVD remote. I wish to activate a solenoid when the DVD remote button is pressed. The circuit is is powered by a 9v ...
2
votes
2answers
168 views

NPN: Not fully sinking to GND

I'm using an NPN to pull a 12v (5mA) signal low from an MCU (logic level). My problem is that when I pull the 12v line low, 7.4v are still present at the 12v side of the line using the circuit below: ...
0
votes
1answer
61 views

555 timer square wave LED flasher

Will this circuit work for the purpose of making a high voltage LED flash on and off at 10kHz? I have a NPN transistor to turn the LED on and off. The pad is where the LED will be soldered into as ...
1
vote
1answer
109 views

Transistor latching circuit

I have made the following circuit from a few online sources, it is very basic but uses two NPN transistors to make a latching circuit that toggles when either push button goes to ground. My Falstad ...
1
vote
2answers
67 views

Using transistor as switch in the “middle” of the circuit

I have an rather complex circuit with button micro-switch in the middle (actually, it's RF remote control with 3 buttons). I would like to be able to simulate the micro-switch click on it with one of ...
0
votes
1answer
64 views

LED cube using 74HC595 and 2N2222

So I'm trying to build an 8x8x8 LED cube according to this Instructables. But I'm using slightly different parts: 74HC595 shift registers instead of 74HC164 2N2222 transistors instead of 2N3904 I'm ...
0
votes
2answers
59 views

ESP8266 GPIO2 - invert logic NPN transisotr

I make big mistake in my design. I connect output to ESP8266 GPIO2 at this pin I got base of NPN transistor to control LED. I test it on breadboard but probably by noise or "universe magic floating ...
0
votes
0answers
56 views

Push-pull transistor - input current spikes and advantage over just an npn transistor

I have simulated the following circuitry in LTSpice: Input Voltage pulse characteristics: Questions: 1. What is the reason for the current spikes on the input resistor R2? Do I need to worry about ...
0
votes
1answer
66 views

NPN transistor won't saturate when Vcc is greater than 7 volts

Am I missing something here? I have an NPN transistor (2N2222) with a 10K resistor from collector to Vcc. Also a 10K resistor from base to input signal. Emitter is grounded. The base input is ...
1
vote
2answers
79 views

Using an analogue multiplexer to control a motor controller?

I am designing a control circuit for a Sabertooth 2x60 motor controller. When this controller is in analog mode, it runs in full reverse (0v control signal) until my software starts and applies 2.5v ...
0
votes
3answers
91 views

NPN inverter alternative that takes up less space on the board

Here I have an NPN inverter circuit which consist of 2 separate NPN transistors and 3 resistors. It does the job, but it takes too much space on the board. Is there any alternative to this circuit ...
0
votes
1answer
552 views

“Normally closed” switch with NPN transistors

Is it possible to have "Normally closed" switch with NPN transistor when the voltage at the base is 0V? So far I only managed to achieve this result with NPN transistor when the base is HIGH. When the ...
1
vote
1answer
80 views

12 V pulses with 100 MHz repetition rate

I have to control an high impedance load (> 25 MΩ) with 12 V pulses with maximum 5 ns of width and a repetition rate of 100 MHz. I can generate the pulses with the required shape using an FPGA ...
3
votes
1answer
198 views

Can a BJT base-collector junction be safely used as a diode?

In a (hobby) project I'm doing, I noticed that the diodes I needed were more expensive than the NPN transistors, which left me wondering if I could substitute the transistors for the diodes. I'm ...
1
vote
1answer
57 views

Question about transitor NPN [ALFA;Strange configuration;Exit characteristic]

first of all thanks for read and for your time, I have a few questions about transistor: 1) I can't understand why my book say: Ic=Icb0+alfa*Ie and not ...