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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1answer
78 views

Constant current limiting circuit

Can someone help me understand the working of this circuit: My questions : Please explain me how this circuit will work in its entire operation range. I am not able to understand the purpose of the ...
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Output transistors on the TL494 [closed]

I am building a SMPS with a TL494 and got stuck on the output transistors to drive the gate drive transformer. I have tried circuits with common emitter and common collector but somehow it doesn't ...
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136 views

NPN circuit (breadboard)

What does this NPN BJT circuit represent, is it a switch or just a PN diode, and what should this plot look like when we sweep the value of Vbe, and why?
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96 views

Can someone explain this part of circuit from BQ500212A?

As the title says, I am struggling to understand what this part of a circuit does. It's part of this evaluation module. Is there any chance the BSS138 transistors will activate without the SNOOZE/...
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LED Controller Circuit Design with BJT

https://www.circuitlab.com/circuit/mthven79a2m6/led-controller/ I designed a LED controller to turn the led on/off. What do u think about my design?
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3answers
392 views

2N2222 low side relay switch not turning off

I've been pulling my hair out over this for weeks and I can not for love nor money work out why it's not working. I have a very standard NPN low side switch setup to turn a relay on/off from a 3.3V ...
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59 views

Why does this 8 step sequencer schematic need two resistors for each output pin?

I've found a schematic online for an 8 step sequencer and built it on a breadboard. Before I start experimenting with it and adding features, I'd like to find out if both 10k resistors are needed for ...
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3answers
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What can I do to get a stable bias on this current sink?

I am still working on trying to get a stable 60 Hz ramp generator with a down-slope, and I am trying to do it from first principles and as simple as possible to understand fully what I'm doing. I got ...
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67 views

Is a resistor compulsory in a NOT gate made from an NPN transistor?

I am making a NOT gate using a BC337/BC547A transistor (tried both) and I have made this circuit (image shown below) using a simulator: This is working properly. However when I remove the resistor R1,...
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My FM transmitter never works, Why? [duplicate]

I'm trying to build a FM transmitter, but without sucess. The current schematic I'm using is this one: The alternating current at the (+) of the op amp is the P2 output of my phone. V3 and V4 are 2 ...
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what kind of transistor is this?

I'm just beginning to understand a bit about transistors and wanted to build my own NOT gate with what i thought was an NPN Transistor. When it didn't work I thought maybe i had the pins mixed up and ...
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How do you get transistor voltage when you only have currents?

β=50 I need to find Vbe and Vce So obviously it is a NPN transistor, the current is flowing in the same direction so it is in active mode. Ie=Ic+Ib 1.2mA=1mA+Ib Ib=0.2mA Vbe should be around 0.7V for ...
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Can a D667A NPN transistor be replaced with a BD139 NPN transistor in this PSU?

I have a PSU that had a D667A NPN transistor that took some damage. I am not 100% sure what its goal is in the circuit, but I have the impression it is used to drive the power transistor mounted on ...
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NPN Transistor problem

I need to find Vce Would this be correct way of solving it? I got 7.551V for Vce
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55 views

BCW71 NPN transistor as a switch

I have a simple circuit using an NPN as a switch using the BCW71 (https://www.mouser.es/datasheet/2/308/BCW71-D-1802620.pdf), as seen in the following picture: My issue is that when I put 3V3 at the ...
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Using a transistor as diode [closed]

What are the advantages of using a transistor as a diode after interconnecting its collector and base?
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How do I connect a NPN transistor so it operates in the saturation region?

I am learning about NPN transistors and I could not find how to connect the transistor so it operates in the saturation region.The circuit that I have made works in the Active region,because when I ...
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125 views

Understanding the 2N2222 transistor, Where is this voltage coming from

I was using Proteus to simulate NPN transistor then I saw this Both Switches are open. Why I see 3.12 Volts
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68 views

Common emitter bandwidth and probing

I am trying to design a simple RF amplifier for a 1MHz AM signal (for low-power transmission). My modulator (JFET-based) outputs ~...
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157 views

Will my 555 timer circuit work the way I want it to?

Essentially, I am trying to implement a safety system for another project of mine. I am running a very high current through a rather large solenoid and want to ensure that a failure in its control ...
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2answers
90 views

Using P-Channel mosfet with arduino

I want to drive a 12v inductive load with arduino (a motor) . This device has 3 wires a common GND and one wire to go in one direction an another one to go on the opposite direction, as it has a ...
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1answer
30 views

Simulation shows mystery leakage

Background: I am trying to design a battery powered gate opener, the basic concept is that if the uC switch is on the relay switches the motor on, but if the actuator gives a low feedback (gate is ...
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79 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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72 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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1answer
56 views

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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1answer
76 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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1answer
62 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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1answer
49 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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30 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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52 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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48 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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1answer
76 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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1answer
31 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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91 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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34 views

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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199 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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46 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
60 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
86 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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2answers
61 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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3answers
102 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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2answers
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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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5answers
1k views

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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1answer
74 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
56 views

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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182 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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118 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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