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 ...

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29 views

Class A Audio Amplifier?

Hi all, So for my senior project, we have to design an audio amplifier, We have these small 3 watt speakers and decided to choose the 2N222 NPN BJT as our transistor. There will be an input of 5 ...
0
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0answers
63 views

Small signal gain of a pnp and npn transistor circuit

Can anyone help me solve this problem as I am unable to get the small signal gain Vo/Vi of this circuit. I got the quiescent collector current of pnp and npn as 1mA. For the small signal analysis I ...
0
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2answers
39 views

NPN circuit to switch 12v 1A DC load by 3.3v 1A DC using PIR

I am trying to switch on a circuit using PIR motion detection. I have a PIR module which outputs 3.3v 1A DC when it detects a motion. I want to switch on a circuit rated at 12v 1A DC. I read some ...
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0answers
24 views

L200 with NPN pass transistor help!

L200 datasheet: http://www.zen22142.zen.co.uk/Circuits/Power/l200.pdf In figure 24: There are two transistors, one BDW51 and one BC108. I was wondering what is the use of the second transistor ...
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0answers
24 views

Proper Capacitor for 555 Circuit with Simple NPN Amplifier

As I understand it, in the classic 555 with a speaker circuit, the capacitor that is in series with the speaker is there to prevent DC from flowing through the speaker: And this capacitor, C1, is ...
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1answer
108 views

Relay Feedback Problem

I am a computer science student working on a project for my Diploma and I am building a DIY PDU, I thought building something would be a lot funner then programming a website like 90% of the class ...
0
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2answers
73 views

TIP120 transistor overheating with heatsink

The transistor gets really hot even though I am using a heatsink. Have I connected something wrong?
1
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3answers
132 views

Driving large common anode 7 seg LED with NPN transistor and arduino, worked but is it the right way?

I'm newbie, the circuit designed myself for driving large LED worked but I'm not sure is there better ways? I have only NPN transistors and common anode 7 segment display. Thank you.
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2answers
1k views

Why would I use 2N3904 instead of 2N4401?

2N3904 and 2N4401 appear to be very comparable parts in all specs. 2N4401 has a higher current rating, but otherwise they look to be about the same in price and everything else. Obviously it's ...
4
votes
4answers
115 views

NPN vs PNP current limiter

So I'm trying to design two mirroring current limiters for a +-15 volt power supplies. I don't understand why these two circuits don't behave more like each other. The PNP circuit has +15 on ...
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2answers
46 views

Not Gate switching

Hello I'm new to electronics. so i've created a NOT GATE with an NPN transistor like that Everything works fine for now but what i want is adding a PNP transistor that will be triggered by the NPN ...
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2answers
51 views

How can I invert this current control?

Below circuit is an emitter follower supplying current to an LED. A DAQ board is outputting 0-10VDC voltage to the base and cannot supply more than 5mA. Thats why the LED is not directly hoked up to ...
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1answer
52 views

2 NPN configuration that apparently works by small Recombination Currents

simulate this circuit – Schematic created using CircuitLab In this configuration of 2 NPNs, how is V_OUT following V_IN? Ignoring recombination current: Assuming conventional current, ...
3
votes
5answers
280 views

How to distinguish PNP and NPN transistors?

I need to know how to distinguish between an NPN transistor and a PNP transistor. If I pluck any transistor from a radio, how can I know its nature using a digital multimeter?
0
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2answers
69 views

SR Flip-flop with 2 npn transistors - initial state

I built a SR flip-flop circuit according to this schematic with two NPN transistors: I read that the initial state of such a flip-flop is undefined. I observed that in my test circuit it's always ...
0
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1answer
88 views

Reason(s) why this circuit works

simulate this circuit – Schematic created using CircuitLab Yesterday, I saw a schematic exactly the same as this, except the voltage connected to the relay was 12 V and different from the ...
2
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1answer
246 views

Voltage regulator using bipolar NPN transistor

I came across a circuit, and I got some questions about it. What is the reasoning behind using the NPN-transistor? What part of the circuit draws the most current?
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0answers
40 views

NPN - PNP Vbe Matched Pairs.. Can I use 2N3906 with 2SC945

I am trying to build the following exponential converter circuit from the Thomas Henry "Making Music with the 3080 OTA" document. simulate this circuit – Schematic created using ...
1
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0answers
59 views

hfe of transistor in active region

I've been studying NPN's and I'm trying to calculate the voltages and currents. Consider the following transistor circuit simulate this circuit – Schematic created using CircuitLab with ...
2
votes
2answers
107 views

Does Transistor NPN only amplify Positive charge? [closed]

I know my question might be a bit "stupid", as I am now a student. I created a circuit like this ... But it does not work. (I mean the DC Motor does not turns.) simulate this circuit – ...
2
votes
0answers
116 views

Modulating UART output with PWM

I would like to modulate a UART output with a PWM signal. I think the following schematics should work. Can you see any mistake? The result I'm expecting: PWM = GND and UART = VCC -> LED is on PWM ...
3
votes
1answer
111 views

What limits the current in a Darlington pair?

I am unsure how the TIP120 doesn't blow up in the given equivalent circuit from the datasheet: I understand that the user will probably use some sort of current limiting resistor before the left ...
4
votes
1answer
45 views

Turning on an LED based on light and darkness?

I know this question has been asked a lot of times and there are a lot of tutorials but please bare with me for one second. I understand the basic concept but based on my simulated results, one thing ...
1
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2answers
75 views

Why load in NPN transistor switch are located in collector circuit?

I make a simple transistor switch. I read the theory and in many sources I saw that load (with NPN transistor as a switch) are connected to collector circuit, not an emitter circuit (pic.1, for ...
0
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3answers
128 views

High Power LED Strobe making a Whining Noise when powered by a PWM signal

I am trying to control/fade a couple of High Power LEDs, these are basically 12V 18W LEDs inside a nice package. I want to use an Arduino and a N-Channel MOSFET to adjust the brightness. I tested ...
1
vote
1answer
124 views

decreasing base current on saturated npn transistor

I would like to know if decreasing the current at the base on a saturated transistor(as in the attached photo) will cause the transistor gain to increase and by that, to maintain the collector ...
0
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1answer
95 views

How to measure a BC-547 transistor's details?

I am new in electronics. What I am trying to do is measuring everything of BC-547 transistor's details from a basic circuit design practically. I want to measure as example: collector-emitter ...
0
votes
1answer
72 views

Comparing sensitivity to temperature changes of BJT (transistor) circuits in Common Emitter Configuration

I measured Ic variation with Ib when Vce = 15v kept constant for BJT (NPN) in Common Emitter config and also BJT Common Emitter config with series 47 Ohm resistor connected. From the experiment I ...
5
votes
3answers
672 views

What does reverse diode on NPN symbol indicate?

Update: A diode in this position is (at least sometimes) referred to as an anti-parallel diode. This term brings up a lot more results on search. I've been scavenging parts from compact fluorescent ...
2
votes
1answer
72 views

what is the collector gain of a transistor?

I was wondering what exactly collector gain is for npn transistors, or more specifically if there is some sort of equation for getting it, and if its value changes as you change the input ...
0
votes
1answer
30 views

V CE in the emitter follower configuration

Is it true that voltage between collector and emitter is 0 in the emitter follower configuration? (We intentionally use the saturation region of the transistor)?
1
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1answer
194 views

PNP to NPN Transistor switch

I'm working on project that requires I switch a 12v power supply on the high side of a circuit, using a 3.3v micro controller. To make this work, I'm thinking a can connect a PNP transistor on the ...
-2
votes
1answer
73 views

about semiconductors

I have got the following doubt. Hope you clarify it. Thanks in advance electron when finishes its life time recombines with hole in valence band . its given that in an pnp transistor holes of emitter ...
0
votes
1answer
79 views

Transistor with emitter attached to another transistor's base

I made a circuit that looks something like this: simulate this circuit – Schematic created using CircuitLab If I touch the loose wire with my finger, the LED will light up. Could someone ...
0
votes
1answer
157 views

BEC or CEB NPN Transistor [closed]

I am looking for a small, inexpensive NPN transistor, similar to 2N4401 in specs, with a BEC or CEB pinout. Does anyone know of any?
1
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1answer
86 views

Forced beta too small

Let's take an example in which the recommended beta for a transistor's(NPN) saturation is 10.If you use a forced beta smaller than 10,will the transistor still be saturated succesfully?Can hFE be ...
0
votes
1answer
52 views

Help to calculate the collector current

Above circuit is taken from a book. It uses an NPN and a PNP transistor combination. In saturation, the author's answer to the Q2's collector current is 4.4mA and claims only 0.6mA of it comes from ...
0
votes
1answer
79 views

A confusion on the current gain of an NPN transistor

In above screenshot V2 is increasing ramp voltage from 0 to 12V, which accordingly increases Ib. Transistor is an NPN type. Ic(q1) is the collector current. Vce = V1 is a constant 1V. So it means ...
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votes
2answers
102 views

No plot for DC current gain in datasheet

Here is the data-sheet: https://www.fairchildsemi.com/datasheets/2N/2N4401.pdf I want to use a 2N4401 NPN transistor in active region for amplification, and I want to know its beta(DC current gain) ...
1
vote
3answers
148 views

Vce too high. Help?

I have been working on a high-powered LED light bar. The design powers them almost directly from the mains, but limits current using a 555 and beefier NPN. Below is a simplified schematic. Obviously ...
3
votes
1answer
441 views

Why am I getting negative base current in LTSpice simulation?

When I was trying to bias an NPN transistor I noticed that the base current Ib is negative in LTSpice. So for the sake of simplicity I only apply voltage to the base-emitter junction. As you see in ...
3
votes
1answer
122 views

BJT transistors AND gate

I am trying to build a simple AND gate using 2 2N2222 transistors and the +5V source from an Arduino board. At first I tried the circuit without the R1 and R2 resistors but the output was 1 when B was ...
1
vote
4answers
121 views

Using NPN-Transistor as switch not working

I have following schematic: simulate this circuit – Schematic created using CircuitLab But the motor is not working, the NPN-Transistor does not seem to let any current through. What am ...
0
votes
1answer
286 views

How to send out 60khz signal from antenna?

BACKGROUND In Japan there are radio-controlled clocks. Time is synchronized by 40khz (in west Japan) and 60khz (in east Japan) radio, which is broadcast from transmission towers. The signal is known ...
1
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1answer
149 views

Finding “beta” in an NPN transistor

I am trying to figure out "beta" value of an NPN transistor, but I am not allowed to measure current directly. (Although I do have access to lab equipment and other components such as multimeters, ...
1
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1answer
134 views

NPN and PNP Built-in Voltage

Does the base-emitter connected BJT have the same built in voltage as the base collector connected BJT? Why or why not?
2
votes
1answer
93 views

What is the purpose of this transistor in an Apple Time Capsule?

While taking apart a 2009 Apple Time Capsule, I found a 2N3904 NPN transistor on a 2-wire cable with the emitter connected to one wire and the base and collector connected together and to the other ...
0
votes
1answer
76 views

Is this NPN transistor AND logic gate practical?

Most places on the internet that I see give a schematic for an AND gate that is something like this: simulate this circuit – Schematic created using CircuitLab The only thing about this ...
1
vote
1answer
90 views

How to determine value of Vbe ON in BJT

I have to do a lab report which requires me to know the value of the base emitter voltage of the BJT in the forward active region. Last week in lab I measured a lot of data points for different Ib Ic ...
3
votes
1answer
323 views

NPN vs PNP at H bridges

Lots of different darlington pairs datasheets indicates that NPN are faster(lower rise and fall times), stronger(has a higher Hfe and bigger current maximum) and because of gate source tension, easier ...