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)
5
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5answers
183 views
Basic Electronics - I want to learn the “why”, not just the “how”
I have been looking for a very basic book on electronics, but many of them explain what the components do (and how they are made) and then go into designing circuits that do stuff. They tell you to ...
4
votes
3answers
91 views
How do I amplify a dc voltage that is too weak to trigger the base in a transistor?
I'm trying to take the voltage output from a 3.5mm audio jack and have it light up an LED according to it's voltage. I was going to attach the left audio cable to the base of a 2222n transistor which ...
3
votes
0answers
42 views
Is there a transistor comparison chart or database to be found?
When picking a transistor, I usually start with my supplier's catalogue and search and refine according to the specs I am most interested in. However, I seem to often come out with odd choices. For ...
2
votes
6answers
90 views
Switch transistor with a low voltage and current
I'm designing a circuit that will use a combination of switches and resistors to allow a microcontroller to identify which switch was pressed based on the voltage read and perform a switch-specific ...
6
votes
3answers
202 views
How does this circuit diagram work?
I don't understand this circuit diagram here, but I'm sure that you can help me out.
I'll explain what I have figured out so far.
EDIT: It's a metronome circuit. Sorry for being unclear about that.
...
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0answers
70 views
Compliance question
Q. You have +5 and +15 volt regulated supplies available in a circuit. Design a 5mA npn circuit source(sink) using the +5 volts on the base. What is the output compliance?
This is what I've done:
...
-3
votes
0answers
32 views
RTL state confusion [closed]
My textbook says that if Vin1 is 0V and Vin2 is 5V, then both transistors are off, but I think that the upper transistor must be in saturation mode. Why is it off?
4
votes
3answers
118 views
How does a dual gate MOSFET reduce Miller effect?
How does a dual gate MOSFET reduce Miller effect? I am trying to gain a global understaning of the physics behind them, not necessarily exact formula's that come with it other than maybe some for ...
0
votes
1answer
75 views
Planning an amplifier using a transistor
I want to plan design an amplifier of tension voltage using a transistor:
but I don't know how I can choose the values of \$R_1\$, \$R_2\$, \$R_3\$, \$R_4\$, \$C_1\$ and \$C_2\$..
I want to obtain ...
-7
votes
3answers
82 views
Why use +5V and not lesser than that in Digital Electronics? [closed]
Explain In Detail why in Digital Electronics the input voltage will only be a 1 or logic high when the voltage supplied is +5V and not lesser than that.
2
votes
2answers
56 views
Problem on output compliance?
What is exactly meant by output compliance of a current source? I've read that it's the range of voltage over which the current source behaves well. What exactly does behaving well mean?
I've got ...
1
vote
2answers
88 views
measuring transistor beta (Hfe) - Ib anomalies explanation needed
I've been struggling with details of building accurate (+-1% tolerance max) beta meter. The simplest idea I came with went to a diagram as shown below, with R set to a value providing 0,01mA current ...
6
votes
3answers
130 views
Transistor Toggle Not Working
I'm trying to learn about how transistors work. As a simple test I created the following circuit:
My idea is that when the second transistor will keep the first one active after I click the button ...
0
votes
0answers
72 views
Is it safe to use a Relay to control my room lights with a microcontroller?
Firstly, I would just like to state that I'm a complete n00b to electrical engineering.
I'm thinking of controlling my room lights with a microcontroller.
The way I'm planning to do it is by placing ...
0
votes
0answers
47 views
adjustable battery indicator
I've got a simple circuit powered by one 18650 LIon battery.
Now i want to light up a LED when the battery voltage drops under a specified value (e.g. 3,4V)
I know it would be easy with a ...
3
votes
2answers
67 views
Controlling LED with 300mV AC signal
I would like to control an LED with audio signal, but the problem is, that output signal is only 150mVpp (with 150mVpp positive offset). In my understanding, it needs to be higher than 0.6V to get the ...
2
votes
1answer
64 views
transistor loop to limit the current
I am trying to implement the DALI TX/RX circuit below.
The description says:
The other transistor (T2) is controlled by the current flowing through the
resistor (R1). If a DALI slave unit is ...
3
votes
1answer
147 views
BJT Differential Amplifier-Long Tailed Pair
I am trying to solve this assignment
Consider this schematic (the BJT's are in the effective area, with
\$\beta=200\$ so as to \$i_e\approx i_c\$). Also \$R_1>>R_E+r_e\$.
Define ...
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votes
1answer
73 views
Multiplex two I2C ICs into four 7 Segment displays
I currently have two PCF8574AN I2C ICs. Is there a way I could have two seven segments be driven off one IC (So i could run four seven segments displays off the two ICs that I have). I have thought ...
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votes
3answers
89 views
Logic Circuits Vs Transistor Power Circuits
I have need to invert a signal to drive fets with hard/fast rise and fall times. I was told in another thread to use an inverter (NOT chip). This makes perfect sense to me since logic chips are ...
5
votes
4answers
263 views
Transistor Delay
I'm attempting to make an alarm for a freezer so that if the door gets left open, after 1 minute or so, an alarm will sound.
I've got something similar to the schematic below. When the switch is ...
3
votes
2answers
68 views
Heat Activated Alarm
I am working on a project in which I have to simulate a heat activated alarm. I have attached two images. One of which is a Proteus circuit image that i have made. When i start its simulation the ...
3
votes
4answers
105 views
Is this arduino motor driving circuit correct?
I got an Arduino Pro Micro and some parts to play with. I want to control a little 5v motor from an external power supply by using the Arduino to trigger a transistor. Like this:
Is that at all ...
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votes
0answers
45 views
MCU 5V to 12V switch [duplicate]
I am new to this and i would really appreciate any help at all
I am making a flasher unit for my car so I am running it off of the 12V cigarette lighter so I have a voltage regulator running my MCU ...
-4
votes
0answers
61 views
How to Switch My microcontroller that is running on 5v to a 12v led array [closed]
I am making a flasher unit for my car so I am running it off of the 12V cigarette lighter so I have a voltage regulator running my MCU and I would like to run a 12V led array. I heard that I can use a ...
-6
votes
2answers
125 views
Simple amplifier Cuircuit [closed]
I am new in electrical transistors. My project is to make a 1 watt audio amplifier. Can anyone provide a best amplifier circuit using darlington pair and 2N3904 transistor. i searched google. So ...
3
votes
2answers
118 views
arduino pulse to transistor power maximum
Hello I want to get a confirmation that what I am doing is not going to fry my Arduino Mega.
The sketch I am using to send a pulse out on pin 8 to a 2n3055 that is switching 12 volts is this:
...
1
vote
2answers
162 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
vote
1answer
73 views
Help identifying/selecting SMD MOSFET
I am repairing an IP camera that has a blown transistor in the power supply section. The transistor looks like a SOT23 transistor, but it has 6 pins (how is that package called, anyway?), 4 of them ...
4
votes
2answers
107 views
what transistor should i use?
My arduino UNO can provide max 40mA and 5V and what i need to control is 2.2V 60mA. I will use 4 shift registers (74hc595) connected to arduino and each shift register output will have a transistor ...
3
votes
1answer
68 views
Find out the specs of a component without manufacturer
Today, I started playing with transistors. I have here some teeny tiny 2n2222-108 transistors.
Actually, it didn't take long before I burned my finger against that transistor... It was really hot. I ...
2
votes
1answer
99 views
Why transistor is non-linear in Cutoff & Saturation mode?
I am imagining Linearity in the sense that
F(ax+by)=aF(x) + bF(y)
Now suppose I have BJT characteristic curve :
In Active region, The response is : Ic = ...
6
votes
2answers
171 views
Switching Between Two Voltage Supplies
I have been trying to work out a circuit something like the following:
simulate this circuit – Schematic created using CircuitLab
I want VOUT to be 3V when the switch is open and 5V when ...
3
votes
3answers
157 views
Turning on multiple leds with arduino using transistor
I want to be able to turn on 50 red LEDs with one pin of an Arduino. I don't want individual control, I just want to be able to turn them all on or all off.
I found this example. It uses a 2N3904 ...
0
votes
0answers
45 views
Amplifier circuit - NMOS mode of operation? Gain?
Ok I have the following circuit, with values of variables:
\$\displaystyle R_{1} = 1 M\Omega, R_{2}=10k\Omega,~~ k_{n}C_{ox}\frac{W}{L}=1mA/V^2\$ , and \$V_{T}=1V\$.
1) When \$v_{IN}=0\$, calculate ...
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votes
2answers
115 views
Open collector logic question
I have an instrument that I am trying to integrate some pumps with. It has 3 Open Drain pins,a ground, and a +5V pin.
I've successfully used 3 NPN transistors to act as a +5V switch to drive a relay ...
2
votes
1answer
97 views
Simplest design approach for PWM control with power MOSFET
I'm designing an application in which the current running into a load is controlled by PWM. A microcontroller generates a PWM cycle at 20kHz and this signal is used to control a MOSFET which is ...
1
vote
2answers
106 views
MOSFET for PWM application
I'm designing an application where a power logic level MOSFET is driven using a 5V PWM signal at 20kHz.
The drain current will be approx. 10A and the voltage of the load 12V.
I looked into the ...
2
votes
2answers
193 views
leds in parallel, switched with NPN transistors
I have the following circuit designed to drive 3 PWM pins off a 3v3 Arduino Pro Mini -- one pin for each of R, G, B in this set of 5 RGB LEDs.
simulate this circuit – Schematic created ...
2
votes
4answers
125 views
Why doesn't a diode or transistor get neutral?
As we learn that diodes and transistors are made by some materials, and they are called P or N according to having extra electrons or holes.
If there are extra electrons on n-type silicon (doped), ...
2
votes
1answer
276 views
Mystery circuit: latching relay control with transitor / capacitor - why doesn't it work?
I've been looking for a way to control a latching relay with a microcontroller that doesn't quite have enough current on the output pins to operate it directly. I found this intriguing circuit using a ...
2
votes
2answers
120 views
Is this a 5V to 3.3V level converter?
Need to repair a legacy system that has been discontinued and am confused by the PNP based circuit below.
The input signal (max. freq = 20Khz) is applied at IN and is active low. It's TTL level.
It ...
1
vote
1answer
142 views
Having difficulties using a darlington (BD681) to drive a 12V fan from an Arduino
I'm trying to power a 12v fan using a darlington so I can control the speed from an Arduino. When I wire up as below nothing happens, even though I'm sending a PWM signal:
Have I wired up the ...
1
vote
2answers
96 views
Will the PNP and the diode circuit behave differently?
Need to repair a legacy system that has been discontinued and am considering replacing the PNP based circuit with the diode based circuit.
The input signal (max. freq = 20Khz) is applied at IN and is ...
0
votes
2answers
80 views
At which negative Vce voltage will an NPN transistor be damaged?
Assuming an open base, how low can Vce go (negative) before the transistor is damaged? Can I protect a transistor by connecting a diode's cathode to the collector and and anode to the Emitter?
If ...
0
votes
4answers
179 views
Transistor and zener diode
I have found this schematic and am confused about the transistor and the diode. I know that the phone voltage is around 3V and the PIC voltage is 5v, and it's a level shifting circuit.
My questions ...
0
votes
0answers
120 views
Drawing small-signal equivalent circuit models - pi vs t model
The difficulty in electronic small signal analysis for me is in drawing the small signal equivalent circuits for multi-transistor circuits. When should the pi model be used in place of the t-model?
I ...
2
votes
2answers
93 views
Constructing a simple emergency light kit
This is my first adventure in the electronics world and, as I'm a CS student, you can expect a lot of associations that maybe aren't that right.
The main feature of my circuit is:
If there isn't ...
0
votes
2answers
167 views
Transistors never work for me
TOday, I have built an LED cube. I put it all together, arduino, mess of wires and all, and it doesn't work. Fiddling with it a little bit, I find that if I short certain wires to ground, the LED's ...
4
votes
2answers
128 views
What transistor to use when building a simple MCU controlled LED blinking circuit?
This is my conceptual schema to use a PIC12 to control the blinking of 3 LEDs with different blinking patterns. I have a few questions that would like to ask.
Is this circuit going to work?
What ...
