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 ...
1
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2answers
161 views
How the transistor NPN 2N2222 works?
I'm a beginner to electronics. I just started to test transistors, but I've some doubts.
I've used this schematic to test a NPN 2N2222:
My questions:
1 - How much Voltage or Amps should the ...
1
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1answer
102 views
How is it possible that shorting base and emitter allows current to pass?
My setup is simple: a NPN transistor is connected to a DC motor and a battery. The series goes like this: positive terminal - motor - collector; emitter - negative terminal. The transistor base is a ...
1
vote
2answers
130 views
How does the collector emitter relationship work with a transistor?
So,
I'm not understanding how NPN transistors really work in this scenario. In this image, I
have highlighted what I understand to be the collector and emmiter. My understanding is
that power ...
0
votes
3answers
165 views
How to control 0 to 110 of AC with microntroller rms output of 0 to 5 v
Is it possible to control high current with small rms voltage?
UPDATE
Do you think that this is gonna work?
0
votes
2answers
83 views
Why is the base currect incorrect?
My multimeter shows:
Ib=218uA why?
But my calculation shows, it should be: 8.5uA
I used the formula:
Ib=(3.1-0.7)/(10k+271k) [I take Beta=270, BC548 transistor.]
What is the problem? Why is Ib = ...
1
vote
1answer
130 views
What NPN transistor should I use?
I need to control a 12v 5A (or 3A if need be) with an Arduino UNO which has 5v and 40mA. I, unfortunately don't know how to read transistor data sheets. What NPN transistor should I get for this ...
7
votes
3answers
588 views
How do I get +5v for loud noise, 0v for silence from Electret Microphone (or other components)?
I have been asking a few questions here to get to a proper one, the initial questions I asked are linked to at the end. I used Fritzing to make up some schematics of my initial thoughts, but at the ...
7
votes
1answer
961 views
Can the Common Emmiter Amplifier use a PNP Transistor instead?
This is a simple Class A amplifier using an NPN transistor:
Is there a way this can use a PNP transistor, instead (with only 0V and +Vcc, not 0V and -Vcc)? Why or why not?
2
votes
1answer
139 views
Using +4V output, to trigger an npn transistor operating on +12V
In a +12V circuit, I am trying to use a proximity sensor, which works on +5V and its output is +4V, and goes 0V when triggered. Using a L7805, I get the +5V for the sensor supply. However, I try to ...
4
votes
2answers
324 views
Why won't my 2 x NPN circuit latch?
I'm working on building a soft-latch power switch. Before I build the entire thing, I'd like to ensure that I can simply latch power on, without adding off functionality. I am wondering why the ...
3
votes
1answer
81 views
Connecting a N.O. grounded switch to a scanning switch matrix
I am working on a project that includes a scanning switch matrix. It also includes a joystick with an integrated push button. I am out of IO pins on the micro, but there are gaps in my switch matrix, ...
5
votes
2answers
430 views
Switching a current with an NPN transistor and a P-MOSFET
Just learning about transistors and I'm trying to clearly understand how to apply them for basic switching, in terms of the two standard cases, i.e., Active HIGH behavior and Active LOW behavior. For ...
-4
votes
1answer
213 views
Typical BJT npn transistor - Change 0-5V sensitivity [closed]
What is it in an npn transistor that determines the voltage "maximum" for the base?
because in a typical npn transistor it is 5V, meaning if you feed 5 volt into the base it will flow 100%, 1 volt = ...
0
votes
1answer
403 views
Reparing a Chinese power supply Unit
My Chinese phone usb charger has gone.
I opened the lid to repair it, and this is how it looks like (picture below).
Actually how it looked like after I removed Q1 for testing.
I suppose it has ...
-5
votes
1answer
282 views
Is it possible to attach PNP counter to an NPN encoder? [closed]
As a follow-up of my previous too generic question
I have a signal generator (shaft encoder) that has 2 NPN outputs.
I have a high speed counter that needs PNP signals.
How can I convert the encoder ...
1
vote
3answers
1k views
How can I convert a PNP to NPN transistor?
I have a circuit which requires a PNP transistor.
I only have an NPN transistor.
Is there a way to convert one to the other given that they have the same characteristics (apart from the npn/pnp ...
4
votes
1answer
350 views
(NPN) Why is the collector current at saturation, less than the collector current in the forward active mode?
Why is the collector current at saturation less than the collector current in the forward active mode? Specifically,
Why is \$ I_C < \beta I_B \$ ?
3
votes
2answers
469 views
Can someone help me understand this H-Bridge?
I have an old RC car but without the transmitter so I built my own Rx/Tx using MCU and 2.4Ghz transceiver, however, I want to use the car's original H-Bridge but not sure if I understood how that ...
2
votes
2answers
230 views
Remote control led has 3 volt power source output I need it to switch on a 12 volt power source to power led array
I have a LED candle that runs on two AA batteries which total 3 V. It already has remote. I want that 3 V output to turn on a 12 V battery supply to a LED array.
I am trying to use an NPN ...
4
votes
1answer
692 views
Current limiters using transistors and diodes
I have been experimenting with simulating current limiting circuits. I am trying to limit current to ~500mA given a fixed 4.8V source. I started a question based on a conventional 2-transistor current ...
5
votes
3answers
1k views
Help needed optimising simple current limiting circuit
I have been experimenting with simulating current limiting circuits. I am trying to limit current to ~500mA given a fixed 4.8V source. I have started using a circuit like the one found on this ...
6
votes
2answers
382 views
Is a large hFE value a sign of damage?
I have been testing a couple of BFY50 transistors that I salvaged using my multimeter. One of them reports an hFE of ~109 (this looks consistent with the data sheet value of 112). The multimeter ...
6
votes
3answers
3k views
In a circuit being switched by an NPN transistor, do power supply and input need the same ground?
I'm trying to make a circuit that will allow me to switch on a relay that will turn on an LED. However, the relay is rated for 12 V, and I only have an input of 5 V, so I'm using an NPN transistor. to ...
2
votes
2answers
494 views
Simplest way to connect a proximity sensor to a PC
I want to interface a PC with a proximity sensor. The one I've been thinking about is this one.
I can see that the output is "NPN, 3 wire, NO" which I'm kind of unfamiliar with. I also see it outputs ...
2
votes
2answers
151 views
Do Fixed Bias BJT 's have a cut in voltage?
I am doing a DC analysis of a Fixed bias BJT and am trying to calculate its collector current. So far I have these following values.
I am using a MMUN2211LT1 bias resistor transistor network.
My ...
6
votes
1answer
621 views
Confused about transistor operation
I'm trying to use a BC108A (datasheet) transistor as a switch for a 12V power supply using the 5V digital out pins on an Arduino Uno board.
I have connected the collector the 12V supply, the base to ...
1
vote
3answers
452 views
Do PNP transistors have low noise?
I read somewhere that PNP transistors have lower noise than NPN transistors. The majority carriers in NPN are electrons where as in PNP they are holes, so I thought the noise would be much be less in ...
6
votes
5answers
508 views
Why is my transistor accepting power from a base?
I have a transistor (NPN, to be exact it's a SS9014). Whenever I run 4.5 V through the base, connect a resistor and LED to the emitter and connect the LED to ground, the LED has a faint glow. Why is ...
1
vote
2answers
308 views
NPN transistor: collector branch question
The circuit below acts as a simple nightlight: when it's dark out, the LED turns on, and when it's light out, the LED turns off.
What I don't understand is why the LED wouldn't always be lit. Why ...
1
vote
2answers
453 views
Wiring proximity sensors to parallel port inputs
I have a couple of proximity sensors that came without documentation. I'm planning to use them as home sensors for a CNC router.
The label says that they're NPN sensors, 6-36 VDC, 200mA. There are ...
1
vote
2answers
317 views
What are the important considerations when choosing a pass transistor and bias resistor for a buck regulator?
The MC34063 datasheet shows this diagram for a buck configuration with an external (NPN) transistor (in order to be able to handle higher loads than 750mA):
Neither the datasheet nor the ...
2
votes
2answers
2k views
NPN Transistor Analysis: How is collector current determined?
I'm trying to understand NPN transistors by reading the chapter on them in Razavi's "Fundamentals of Microelectronics", and it says that collector current (Ic) is a function of the base-emitter ...
1
vote
1answer
241 views
NPN as toggle switch
I have a very old printed circuit board here that is used to control 2 pneumatic cylinders. There are 8 solenoid valves that control if the air goes in or out to a side of the cylinder.
Now the ...
4
votes
2answers
907 views
How do I tell if a transistor is bad?
I have just had a frustrating experience with an NPN transistor that came from a pack of 15 "switching transistors" from Radio Shack. The specs on the packaging say "Typical hfe: 200" but when I ...
0
votes
2answers
168 views
Harmful to NPN transistor if collector circuit is broken?
Is there any harm to having a conventional switch that can open the circuit between the collector and +V with an NPN transistor? While the base is still being excited by a pin of my controller?
I am ...
2
votes
3answers
2k views
Help with TIP122 darlington transistor
i want to use the TIP122 darlington transistor with my atmega8 to control a 3A 12V geared DC motor. i found that the current gain is 1000 for tip122 from its datasheet. so the base current for 3A ...
1
vote
1answer
6k views
What's the difference between NPN and PNP transistors?
This is not a duplicate of this question.
I would like to know what the differences in their characteristics are. I'm thinking for example about their majority carriers (electrons for NPN, holes ...
