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.
1
vote
2answers
54 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
45 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
31 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
38 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
57 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
68 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
76 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
78 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
74 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
95 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
53 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 ...
0
votes
1answer
31 views
Half H-bridge using only ntype mosfets or npn transistors
Would the following circuits work? I keep thinking I need a mixture of ptype and ntype mosfet or npn and pnp transistor for a half h-bridge, but I keep seeing schematics with only ntype mosfets or npn ...
0
votes
1answer
101 views
Trouble turning on relay using PNP transistor
I am having problems turning on this relay:
https://omronfs.omron.com/en_US/ecb/products/pdf/en-g6qe.pdf
Using a transistor whose base is connected to a digital signal of an Arduino Nano.
The ...
5
votes
4answers
790 views
Constant Current LED Circuit
In the below circuit, the circuit maintains a constant current on LED.
My question is after the LED there is a voltage of 18V, still, need to be dropped. Will the NPN Transistor heat up while ...
0
votes
0answers
30 views
MCP73831 stat pin current
I'm trying to implement a bi-color LED connected to a Microchip MCP73831 battery charge management controller, so I can switch between red and green LED output. Currently my circuit is mixing them ...
1
vote
0answers
96 views
Why do I have voltage on Collector and Emitter when NPN transistor turns on? How to get rid of it?
I have a 2N3904 NPN transistor. I'm feeding the base 5V. the transistor turns on just fine and it shorts the collector and emitter. However, when I turn my meter on volts, I read around 1- 1.5 volts ...
1
vote
2answers
43 views
Spike in RTL Inverter
I do not understand the cause of this spike which can be observed in an RTL inverter (but also in a CMOS inverter). In the following image it is the peak at 10 mS (I have considered as input a signal ...
0
votes
0answers
48 views
Driving transistors without using MCUs
I'm trying to drive transistors with just a push of a button without using a MCU. The circuit I drawn drives different transistor on every button push and resets back. First part is a debounce circuit ...
0
votes
1answer
94 views
NPN Transistor common emitter calculation
I built the following circuit in LTSpice using the default NPN BJT model (beta = 100).
I calculated the Ib to be 115.754uA.
This is how I did the calculation:
Equivalent voltage at base is:
...
0
votes
0answers
35 views
Using a PNP to enable a NPN current source not yielding expected current
Hi I am trying to switch on a brake light with a reed switch. The load is a 12v (0.1A) LED bike light. The following circuit works in the sense that the light comes on when the magnet moves away from ...
2
votes
0answers
97 views
complementary transistor pair npn/pnp in the Kapustinsky circuit
I need to create an old circuit that reproduces fast impulsion, the Kapustinsky circuit (see the picture).
This circuit is 33 years old, and a transistor (or equivalent) does not exist anymore, the ...
0
votes
2answers
69 views
How can I dampen current spikes when using NPNs to drive an LED
Hi I have the following circuit, its purpose is to flash an LED once per second. I'm using a pair of transistors as a constant current source but I observe current spikes of 20% or so when it is ...
0
votes
1answer
83 views
How to set fixed bias on transistor 2N2222 for certain specifications?
I'd like to ask how to set fixed bias for this transistor.. It doesn't seem to be working. If anyone know how to calculate it, please tell me.
I wanna adjust two resistor values so that Uce = 5,44V, ...
1
vote
2answers
111 views
555 timer circuit switching automotive solenoid with PNP & NPN switching transistors
I am trying to design a 30 second timer circuit to switch an automotive solenoid that draws about 0.8 amps, and need some help please.
StackExchange posts have been very very helpful so far, and by ...
1
vote
1answer
79 views
BJT common collector amplifier with a voltage gain sligthly higher than one
How could I explain why a common collector amplifier has a voltage gain higher than one ? In a lab session, I built this circuit :
With Vg=30 mVpp and Vcc=15V, students were asked to give the voltage ...
0
votes
3answers
91 views
How to configure NPN transistor as switch and adjust current flow?
Consider the following circuit:
As signal a 100 kHz square wave (between 0 and 5 volts) generated by an Arduino.
I want to control the transistor so it will let the current from the supply pass ...
0
votes
1answer
50 views
What to do when you don't find an electric component in Proteus?
I am looking for this component: KSC1815. It is a NPN Epitaxial Silicon Transistor
The datasheet is here: http://www.futurlec.com/Transistors/C1815.shtml
But when I try to pick that component in ...
0
votes
0answers
44 views
Base of transistor HIGH without input [duplicate]
I'm having trouble with a simple AND gate, using two 2N2222 NPN transistors:
For some reason, the base of the second transistor is high at 2.9V and I don't know what's causing this. I have verified ...
0
votes
3answers
76 views
Replacing NPN Transistors that failed with similar/better?
I have done some research about this before hand(https://www.electronics-notes.com/articles/electronic_components/transistor/choosing-replacements-transistors.php). I have a switching 12v dc power ...
0
votes
4answers
144 views
Controlling 12V Magnetic Latch Solenoid with RaspberryPi 3b
As the title says I am trying to control a solenoid with a raspberry pi. I am currently using an npn transistor (will post link with parts at the bottom) however I am having a hard time getting it to ...
0
votes
0answers
48 views
Confusion with 555 transistor relay driver
This is probably schoolboy stuff, but before I construct it ...
A 555 will output almost the supply rail, or down to zero. A transistor attached to that, with a relay on collector can drive a 12v ...
0
votes
1answer
98 views
In an NPN transistor, why doesn't current flow without applying a base voltage?
In an NPN transistor, why isn't a typical C-E voltage sufficient to overcome the internal resistance of NPN junction directly? Since we only need 0.7V to overcome the PN junction from the Base to ...
0
votes
1answer
113 views
How does this BJT affect the circuit? If it does, how should I simulate on Circuitlab to see the effect?
I am trying to understand how NPN Q23 in the picture below affects the operation of the left circuit.
If it doesn't then what we get is the circuit on the right with the only transistor now being Q30....
0
votes
0answers
73 views
Find voltage across load resistor
Here the zener voltage of the zener diode is 3.3V and base to emitter voltage drop is 0.7V. What is the voltage across the load resistor and how to find it?
0
votes
1answer
39 views
Voltage Circuit Switch with BJT
I have Found One Circuit Which acts as Switch to Pass 15NV (15 Negative Voltage) to Opamps Negative (-VCC) Supply But I am unable to understand its working . Why Two NPN are used in this Circuit ? ...
0
votes
2answers
112 views
DC current gain in complementary transistors
In Class-B amplifiers complementary PNP-NPN transistors are used, e.g. TIP2955 and TIP3055. https://www.electronics-tutorials.ws/transistor/tran_3.html says that
They both have a DC current gain, ...
1
vote
0answers
50 views
Off load voltage in npn transistor as a switch
There is transistor tutorial on sparkfun.com (https://learn.sparkfun.com/tutorials/transistors/all). I am wondering why there is 1.3 V drop depicted across the LED1 on the picture, since when the base ...
0
votes
1answer
80 views
What is function of the resistor in series with bypass capacitor in npn transistor amplifier?
I am new to electronics and recently I was learning about npn transistor as an amplifier. I tried to build one in ltspice XVII.
This is my circuit diagram:
but the output was not as expected as ...
0
votes
1answer
94 views
Output current in collector of BC107
I am working on following circuit involving BC107 NPN Philips TO-92 transistor and voltage source of 4.2 V.
simulate this circuit – Schematic created using CircuitLab
I got some confusion when ...
0
votes
3answers
76 views
PNP and NPN transistor characteristics for this project (see link inside for schematic)
I'm working on this project
https://github.com/diyhue/Devices/tree/master/HueDimmerSwitch
I would ask which characteristics I need to keep in consideration to choose that two NPN and PNP ...
1
vote
0answers
35 views
Switch resistor with n-channel MOSFET not working
So I try to amplify a photodiode signal with an operational amplifier.
As I want to amplify two signals (1 for a high-intensity light and 1 for a low-intensity light) I sort of need to design a ...
0
votes
0answers
35 views
Why is Ic constant in the plot of Vce vs Ic in a common emitter NPN transistor (in active region)?
In this plot, when \$V_{ce}\$ increases in the active region, shouldn't \$I_c\$ also increase as more electrons are getting diffused into the collector?
Then, why is it that for a large range of \$V_{...
0
votes
1answer
59 views
2-stage BJT CC-EC amplifier [closed]
Using proteus I designed this amplifier:
But I got this result:
I don't know what is the problem in my design. I've been changing the values of the linking capacitors but didn't get any result.
0
votes
1answer
91 views
Need help with three-stage transistor amplifier in LTSpice
I am currently attempting to design an amplifier in LTSpice for an E1 project. My professor tends to emphasize analysis of these circuits, so he hasn't really given us any kind of a design process to ...
1
vote
2answers
89 views
Which region is the transistor operating at?
PNP and NPN transistors in the circuit have identical Is values. Based on the PNP transistor is connected to a DC voltage source.
k = 1.38064852×10-23 J/K
qe = 1.60217662 ×10-19 C
Is = 0.69 fA at 17°...
0
votes
2answers
130 views
Brake DC MOTOR circuit
I have a DC motor that is controlled with an npn transistor with pwm. Everything works fine. I want to brake the motor instantly. I tried to short the terminals with another pairs of transistors but ...
-3
votes
2answers
139 views
Transistors why do they amplify current?
Ok guys I can't understand a thing of the Transistor here is the scheme:
My teacher said that when I put 0,7V on the base the PN junction between Base and Collector is direct polarized so the whole ...
1
vote
1answer
69 views
Need help understanding PNP Base into NPN Collecter circuit for LED Array
I am a novice in circuitry and I'm trying to make an 8x8x8 LED Cube using an instructables guide for a school project. I have ordered all the parts and was testing the grounding circuit for each layer ...
0
votes
1answer
43 views
Is resistor needed to drive NPN Transistor from EEPROM
I am using this EEPROM in read mode: http://ww1.microchip.com/downloads/en/DeviceDoc/doc0270.pdf
And am using this transistor: https://www.onsemi.com/pub/Collateral/P2N2222A-D.PDF
I need my EEPROM I/...
1
vote
1answer
219 views
Arduino - Using NPN transistor as a switch to pull-up/down analog pin
Let me start by saying that I am not an EE, and my knowledge in Electronics is basic, so please bear with me and be patient if, initially I am bending a few rules.
In Epee fencing, a touch is awarded ...
