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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1answer
39 views

NPN BJT non-inverting simple amplifier [on hold]

How to use an NPN BJT as a non-inverting amplifier with a pull-down resistor? (as opposed to using it as in textbooks as an inverting amplifier with a pull up resistor)
0
votes
1answer
40 views

Extrapolating Transistor DC Current Gain Graphs?

I'm working on a design which will use a BJT to switch 2 PMOS gates low to power 2 separate loads. I am going to drive the transistor from a NOR gate. From my transistors datasheet, I thought I could ...
-1
votes
1answer
45 views

Connecting Cathod Commond RGB Leds in parallel with arduino

I'm just starting with arduino, and want to light up 2 RGB leds (common cathode), and just think that the only thing I nedd was connecting them in parallel, no extra parts (my mistake), then I read ...
3
votes
1answer
137 views

Odd NPN Circuit behavior

I've seen lots of useful threads here over the years but this is my first post. I'm building a little box to switch an output based on RPM's watching the ground of an the primary ignition coil on an ...
0
votes
3answers
60 views

Does N-type or P-type semi-conductor show electrical effect?

I am reading the book Electrical Engineering 101. It's a book of basics for not-so-newbie. It contains below description in Chapter 3: A diode is made of two types of semiconductors pushed ...
-1
votes
1answer
62 views

How to simulate BJT cut-off in SPICE

In BJTs, when applying the parameter of collector and base current cut-offs, everything below a given cut-off current gets floored to 0mA, right? So say if we have a configuration with good voltages (...
1
vote
2answers
84 views

Issues with NPN Transistors and RGB LEDs (Common Anode)

I have a question regarding the use of NPN transistors in an RGB LED (common anode) circuit connected to an Arduino Uno. I have spent the past several months developing LED color control software that ...
0
votes
0answers
41 views

NPN Transistor BE & CE flow?

When it comes to using a npn transistor as a switch that controls anything running off of a different power supply. Is the most important thing to keep in mind the difference in current between the BE ...
0
votes
1answer
116 views

Help With My Motor Controller Circuit Diagram

I'm a novice when it comes to electrical engineering, primary since I'm a programmer. However, I am trying to make a drone for fun and I made a really(REALLY) basic motor controller with some NPN ...
0
votes
1answer
83 views

Calculate Base Resistor in a NPN transistor switch

I am building a switch for a buzzer that will charge up a capacitor and sound the buzzer as they hold the button down. When they release the button the buzzer will fade away as the capacitor ...
0
votes
0answers
85 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
votes
2answers
48 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 ...
0
votes
0answers
38 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 (...
0
votes
0answers
27 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 ...
1
vote
1answer
111 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
votes
2answers
83 views

TIP120 transistor overheating with heatsink

The transistor gets really hot even though I am using a heatsink. Have I connected something wrong?
1
vote
3answers
159 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.
10
votes
2answers
2k 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
124 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 ...
0
votes
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 ...
0
votes
2answers
57 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 ...
1
vote
1answer
54 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, current ...
3
votes
5answers
356 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
votes
2answers
81 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
votes
1answer
89 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
votes
1answer
258 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?
0
votes
0answers
52 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
vote
0answers
63 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
115 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
137 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
125 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
46 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
vote
2answers
82 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
votes
3answers
151 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
132 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 current....
0
votes
1answer
97 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 voltage,...
0
votes
1answer
82 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
686 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
75 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 voltage/...
0
votes
1answer
32 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
vote
1answer
222 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
74 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
174 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
vote
1answer
105 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
56 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 R3....
0
votes
1answer
83 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 ...
-3
votes
2answers
108 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
152 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
470 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 ...