The transistor is a semiconductor device that can amplify signals and switch power. Most used types are bipolar (BJT, for Bipolar Junction Transistor) and MOSFET (FET, for Field Effect Transistor)

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Fundamental questions about BJT transistors?

Take a standard NPN transistor. The doping of each element of the transistor is in the name. This is what is inside the transistor... The left "slice" of silicon is doped with an impurity which ...
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52 views

Led Driver/Controller for 3.3v & 5v circuit

PWM Circuit for 3.3v & 5v logic controllers @ high ampere With a 5m LED Strip (14.4W/m), a regulated 12v 10A power supply (120w) and lots of microcontrollers (Arduino Uno, Arduino Micro, ...
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74 views

Confusion with transistor modes

I am having trouble understanding the three operation modes of a transistor. I am giving below the three operation modes (CB, CE and CC) for pnp and npn transistors. and for npn , here it is. ...
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1answer
60 views

Calculate values of resistors

How to calculate values of R1, R2 and R3? R4 is a load 40 Ohms 300 mA. R3 is connected to ATMega8 output. hFE3 of DB136 and BD135 is 40
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1answer
25 views

Discrete IC Printed label

How can I identify a transistor PMOS, when I only know the printed label/legend in it "T9F"? and the same to identify a zener or diode, when I only know the printed label/legend in it "2U90"?
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2answers
60 views

Voltage and Amperage in relays

i have a relayset for Arduino where i find these numbers on each relay: 10A-30VDC 10-28VDC Now, id like to connect that relayset with external devices that run 12V and all the way up to 35A. I was ...
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2answers
47 views

FET atmega168 - transistor needed?

I'm trying to make a BLDC controler, and I'd like to use an atmega168 as microcontroler and N-FETs (x3) to control the motor. The microcontroler will output a PWM that will control the motor's ...
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6answers
157 views

Would it be possible to make a solid state transistor by hand?

I am curious, would it be possible to fabricate a modern BJT/FET transistor with hobby/garage tools only if size and aesthetics was not important? Which materials would one use and how would one ...
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34 views

Sense voltage, Increase resistance

I'm looking for a component or circuit that can sense 3.3V across a pair of leads (call this Circuit A) and ideally decrease the resistance across another par of leads (call this Circuit B). In other ...
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1answer
111 views

MOSFET transistor

Circuit a) presents the circuit of polarization of a MOSFET and b) the equivalent model of small signal on \$g_m\$ is the transconductancy of the dispositive, and \$r_0\$ an equivalent resistance ...
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2answers
177 views

Understanding a 2 transistor oscillator?

I asked a question here about why I was getting a sawtooth wave from a two transistor oscillator. While that question is answered, I don't understand how the circuit produces oscillation in the first ...
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1answer
80 views

2 NPN Transistor Square Wave Oscillator?

I have built the circuit found here. I substituted with 22K resistors at R2 and R3, and substituted C1 and C2 with .022uF capacitors. These are all the components I have lying around. Everything ...
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84 views

Why would MOSFET transistor heat up?

I had a circuit on PCB. I used solder with acid-core to solder it. This combined with my mess soldering caused various shorts between components. One of those components was MOSFET transistor BUZ11 ...
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4answers
79 views

Switch from 3.3V to 24V Raspberry Pi

I want to convert the Raspberry Pi's 3.3V output to 24V as this is what the I/O uses on the Universal Robot arm, UR5. The 24V is supplied by the UR5 and so I thought that a simple NPN transistor would ...
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1answer
56 views

Can a 12v base signal be used to switch a v5 device through a transistor?

I see lots of examples of using low voltage (like from a microprocessor) to switch 12v. I want to do the opposite. Is that okay to do, or should I use a relay? What other components will I need? The ...
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1answer
101 views

Why PNP transistor might be opened even though (almost) nothing is connected to the base?

I have a simple printed circuit board with simple circuit on it. Very beginner. No SMD. As a part of this circuit I have transistor BC557. If I don't solder the base pin of this transistor and test ...
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2answers
96 views

Why does 3-to-5 volt with transistor not work the way it should?

A quick google for "3v to 5v transistor" gives me dozens of circuit diagrams that look like option A below with a NPN transistor and a pull-up resistor. If I build the diagram in iCircult, it work as ...
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1answer
96 views

555 fading in&out if possible with pwm & led array

i'm new here and also in the electronics world so pls be patient with my ignorance. I's now months that i'm fascinated by the 555 timer. The stuff you can do with such a tiny thing is impressing. ...
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2answers
46 views

list of general purpose smd transistors, diodes and mosfets [closed]

I want to start with building up a little stock of smd components. But i'm not sure where to start. Is there a list of general purpose smd Transistors, Diodes and (mos)fets? Thnx in advance
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1answer
87 views

Calculating Voltage Drop over a transistor

I have the circuit below with a Bipolar NPN transistor I have a whole bunch of currents measured with the Amp Meters for various different resistances. How do I calculate the drop in voltage across ...
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2answers
126 views

Using PNP instead of NPN merely requires one to make circuit upside down and reverse current direction, why do we not just use one of the two types?

Using PNP instead of NPN merely requires one to make circuit upside down and reverse current direction, if this is true then why don't we just do everything with NPN transistors? Are there any ...
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0answers
122 views

Raspberry PI PWM Common Anode 5v 12v Lamp Circuit

i'm not an Electronical engineer, i prefer to write codes. But lately (since about 2-3 months) i finally had the balls to connect something to the raspberry PI's gpio. Two days later i already tested ...
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1answer
37 views

e13007f npn transistor datasheet reading for turn on time

I am reading datasheet for e13007. You can get it here: http://www.datasheet-pdf.com/datasheetdownload.php?id=520587 (click on "Download PDF for PC") In "Electrical Characteristics" section under ...
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3answers
47 views

jfet preamp output attenuated and clipped on bottom rail when connected to codec

I am currently working on an embedded audio processing system for electric guitar. I have constructed two JFET preamps (left and right channels) based on the j201 transistor using the common source ...
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3answers
74 views

Detecting electrons as they tunnel through the band gap of a P-N junction

As a learning exercise I'd like to try creating a random number generator using reverse-biased BJTs. As I understand it, if the emitter is saturated in reverse bias, occasionally electrons will ...
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1answer
67 views

transistor command short circuit [closed]

In the circuit below (schematic diagram), the command from a microcontroller allow to send the 5V to the output through two transistors command Q1 and Q2. simulate this circuit – ...
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1answer
39 views

Sanity check my first project: to control my air conditioner with a Nest

I have a window air conditioner. It works well but is a bit old — new enough to be electronic, have a remote and a digital display, but not new enough to turn on from my phone or do anything smart ...
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2answers
63 views

Transistor help

I've read some info on transistor about how it works. So let's say I savaged a receiver from a remote control car which generates 1.2v output from the receiver when signal is transmitted from the ...
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2answers
97 views

Advantages of depletion mode FET devices over enhancement MOSFETs

I've grown the impression that JFETs and depletion mode MOSFETs are not used very much nowadays, especially in new designs. I know that they need different bias networks, especially as discrete ...
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2answers
45 views

Magnetic pulser circuit

I am trying to recreate this device from: The housing 14 is shown with a control panel 16 for purposes of illustration. In one embodiment of this invention, the control panel 16 includes only an ...
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3answers
40 views

Kn2222A darlington pair + a relay, not functioning at low currents

As the title explains it, I have Kn2222A x2 transistors connected as a Darlington pair connected at the ground side of a [JQC-3F (T73) 5v] relay The relay is connected to a 5v power supply. the ...
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2answers
74 views

Switching bjt transistor with photodiode

Initially I thought this would be a pretty simple problem, but I'm just getting started learning electronics so I would love some assistance. This is my circuit: I calculated the values based off ...
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27 views

Finding the input capacitance of this critical path

Hi so I'm trying to find the input capacitance of this critical path and then find the EF, Electrical Fanout, Cout/ Cin. Cout is given to be 10pF Okay here's my attempt at solving this. We know ...
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3answers
62 views

Light intensity is dropping on large LED bulb display when it sequences

I have assembled an LED display controller using an Arduino Mega 2560. The controller runs a display sequence on an array of (25) large LED bulbs that draw about 125 mA each. It also has a smaller ...
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1answer
53 views

Can I use serial communication for audio amplifier remote turn on?

I have a cheap Chinese tablet/GPS/dash-cam in my car. The problem is that I can't hear driving instructions on GPS as the volume is too low. I don't want any external wires for additional speakers and ...
2
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1answer
98 views

Using NPN BJT with a P Channel MOSFET to switch 3.3V to 24V

simulate this circuit – Schematic created using CircuitLab I have some 3.3V I/O on a PC Board. When an output is switched on, I need to switch the 3.3V output voltage with a +24VDC and ...
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6answers
805 views

To what are transistor's “E, B, C” voltages relative to?

I've seen \$V_{CE}\$ and \$V_{BE}\$ in context of transistors, where they clearly denote a voltage between two points. But then I also see things such as: From a table in Wikipedia: ...
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4answers
58 views

Is the hfe of a transistor dependent on the resistance on the other parts of the circuit?

I have a circuit using a NPN transistor with a motor before it and a pwm into the base. The motors draws a current of 600mA if I plug it directly into the power source, just under the maximum allowed ...
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2answers
113 views

Simple transistor circuit

I have been studying transistors and decided to try my knowledge in my lab to find out that nothing works as I thought it would.. I had a small lamp 12V and a handful of 2N3904 transistors, along ...
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1answer
92 views

Transistor Amplifier Circuit

I need your help Given: AC beta (Bac) = 160 Ie = 3.8 mA Find : a) Rin (TOTAL) b) Rin (BASE) c) Av (voltage gain) I am uncertain of the process. I have Rin (Base) = Rs + R1||R2 or is it ...
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1answer
57 views

Use Arduino(5V) to switch a 3.3V

I have a HDMI switch that I want to control with an Arduino. It's working by pressing a button to change input signal. The button is NC(Normally Close). By pressing the button you break the 3.3V going ...
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1answer
25 views

Polarity of feedback in a feedback circuit

How should I check whether the given configuration has a negative or positive feedback. I am stuck because, I know that as Vin increases the drain current will increase but after that I don't know ...
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1answer
50 views

How to use 2 power supplies in transistor key?

I have 2 power supplies in my scheme, one is from Raspberry Pi GPIO and one is 9v battery. I need GPIO output to work like a button, e.g. when output from GPIO is 1, battery should power the scheme ...
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6answers
161 views

Implementation of a NOT gate with two transistors - Why not one?

I just encountered this implementation of a NOT gate: My question is: Why do we need the lower transistor? Why can't we do this: Thanks!
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1answer
106 views

Burning out relays when supposed to be within ratings

I am using this Normally Closed Relay on a 24V circuit: DataSheet The circuit is 24VDC source, which I measured the Amperage in series to be 29mA at the highest. I've breadboarded a lower voltage ...
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0answers
34 views

433 Mhz + Attiny85 improve range

I want to send information from my Attiny85 to my Raspberry. For the moment. Attiny and Emitter work on 5V Emitter have a 433 Mhz 1/2 waveform antenna I'am using virtual wire Raspberry receiver work ...
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1answer
124 views

How do I calculate the base and collector current in this circuit?

I have the following circuit, using a BJT NPN transistor: How can we calculate the current going into the base and collector? I was thinking of using Kirchoff's current law: \$I_1 = I_b + I_c\$ ...
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2answers
136 views

Simple circuit to convert a toggle switch turning on into a short pulse

I need to convert a permanent high signal into a short high pulse. I've got a design problem where I have a toggle switch that connects to a variable +11V to +17V power source, providing a signal to ...
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1answer
73 views

Who triggers transistors to become H/L?

Admittedly that's quite a beginner question: When I learned that transistors work like relays and produce the digital values 0 and 1 what I always asked myself was: they have to be triggered by ...
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1answer
80 views

How do I energize a 12v relay coil using a 2N2222 bipolar transistor?

I'm relatively new to working with transistors, and I'm having some trouble getting this circuit to work. I want to use an Arduino's I/O pins (5V out) to energize a 12V relay coil. To do this, I'm ...