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)
1
vote
1answer
24 views
NMOS Transistor Voltage Range For Specification?
I have a homework question I'm a little confused about. I was hoping for a point in the right direction. I am given the
\$K_n\prime\$ \$(400 \cdot 10^{-6} A/V^2)\$
and threshold voltage (0.4V) for an ...
1
vote
1answer
66 views
Operate a relay from HT12D's output
I'm using the HT12D remote control decoder (and HT12E remote control encoder) to send some data using RF and I have done so successfully.
Now, I want to operate a relay depending on the output of one ...
0
votes
2answers
87 views
How to multiplex a two-way data line?
I have a use-case where I need to control 4+ sonar sensors with a pic 628A microcontroller. The pic is also responsible for controlling a GPS and LCD so pins are scarce. The sonar sensors each have a ...
2
votes
1answer
53 views
Switching between circuits, transistor-based SPDT?
I want to use a piezo buzzer alternatively as a sound detector and as a sound emitter, on the same circuit (be gentle, this is my first attempt to electronics since the university long years ago).
I ...
-2
votes
1answer
55 views
I'm looking to create a simple circuit of flashing christmas lights to music and need help [closed]
I'm not trying to do anything fancy, just get the intensity of the lights to synchronize with the music. I'm currently looking at using a tip31 transistor, about 50' of LED lights, and an aux cable to ...
0
votes
1answer
86 views
Can't turn ON transistor from output of comparator?
I can't seem to turn on a 2n2222a with the output of a LM339 comparator, as soon as the base is connected to the output, directly or with a resistor, even if the output is 5 volts, 9 volts, I always ...
4
votes
2answers
91 views
How is lithography actually used to “print” transistors?
In one of my classes, we skimmed over lithography, but mostly the optics side of things (the diffraction limit, liquid immersion to increase angle of incidence, etc).
One point that was never ...
2
votes
2answers
96 views
Using a transistor to add to max current output from a opamp?
I thought I understood transistors but now I'm confused again.
I have a basic opamp circuit to amplify the input of a electret microphone. The output of the opamp will vary within 1-4V. Now I want ...
8
votes
2answers
187 views
How can I effectively reduce the voltage needed to activate a transistor?
I have built a circuit which basically connects the line out (audio output) of a music playing device to a set of LEDs (actually a huge strip of around 200 LEDs), so they flash in time with the music ...
0
votes
1answer
42 views
How is the induced gate voltage adjusted in a transistor?
I'm looking up a bit on transistors and how they are built up and I know you can use transistors as on/off switches.
How do you adjust the voltage that is induced into the gate creating the stream ...
1
vote
1answer
76 views
Homebrewed phototransistors - unijunction versions
Back in the days, when phototransistors were hard to get (especially in some parts of the world like the communist eastern block), one could brew their own by just filing/sawing off the top of a TO 18 ...
-2
votes
0answers
50 views
How Much Do You Think It Cost To Manufacture Bitcoin ASICs? [closed]
I have for a while heard about GPU/Parallelized Bitcoin mining, but one thing I didn't know of until recently was Bitcoin mining ASICs. I read a bit into it, and one of the CEOs of the startup ASIC ...
2
votes
2answers
126 views
Is this switch circuit correct?
This is a follow-up question to How high is "high impedance" on this chip (CD74HC125E)
I finally decided to use a pn2222 transistor to act as a switch that activates the transmitter. The ...
3
votes
2answers
117 views
Why N-channel MOSFETs are better than P-channel MOSFETs?
Besides the reason that electron mobility is higher than hole mobility, what are the other reasons of preferring an N-channel over a P-channel MOSFET?
1
vote
1answer
58 views
Impedance between BJT base and ground of a common emitter amplifier circuit
What is the impedance between the base of the BJT and ground of the common emitter amplifier circuit? The answer should be in terms of RE and hfe (the small current gain of the transistor). Is this a ...
1
vote
5answers
168 views
Is BJT a Voltage controlled device or Current controlled device?
I have searched already for this question, but everywhere I see debate instead of clear answer. Though it is not that important of a matter whether we call it a voltage controlled device or current ...
0
votes
1answer
65 views
MOSFET commutation problem [closed]
I have a problem with the MOSFET commutation. The fall time is very slow when the load resistor has a low value. It seems like there's a capacitor. However, this doesn't happen when I use a BJT ...
1
vote
1answer
174 views
Why this transistor logic as switch is not working?
I am new to transistors and have read little bit about them. Please let me know if need to supply additional information to debug this issue related to transistors.
Something about my project:
I ...
2
votes
2answers
141 views
Should I design with “N” parts or newer parts?
I noticed there are parts with "N" in the part name, for example the 1N4148 diode and the 2N2222 transistor, etc. What is the history of these parts? Where did they come from and why do they have ...
0
votes
2answers
98 views
> 20 Minimum Hfe on a BJT Power Transistor?
I'm having trouble finding what I want due to the way mouser.com limits searching on BJTs. I'm trying to find out if anyone manufacturers a medium to high power BJT with a gain of at least 30. The ...
4
votes
2answers
595 views
Single LED single transistor circuit not working
I was making a circuit with 1 LED and 1 transistor. pretty primarily i was trying to use the transistor as a normal switch. Here is the diagram below.
So, this is an NPN transistor and i connected ...
0
votes
2answers
76 views
Transistor current limit circuit - power handling?
I am designing a simple current limiter, which charges a large (4.7mF) capacitor with a charge current of (roughly) 500mA from a supply voltage from about 10-20V - see the below circuit.
My dilemma ...
1
vote
1answer
66 views
AH276 hall effect sensor with microcontroller (sensor already in circuit - brushless fan)
I'm currently trying to read an AH276 hall effect sensor using an AVR microcontroller. The sensor is built-in in a brushless fan I'm using and it's operating as the fan's controller. The sensor has ...
2
votes
3answers
86 views
Substitute a MOSFET in a motor controller
I'm trying to build a CoffeeBot from MAKE magazine, and I had a question about one of the components. The circuit is pretty simple; it uses an Arduino to control a gear motor via a MOSFET transistor. ...
1
vote
2answers
74 views
Voltage Controlled Attenuator
I'm trying to create a DC voltage attenuator which linearly scales the loss relative to an applied control voltage "Vc". In other words, K = Vout/Vin is a linear function of Vc. Vin is guaranteed to ...
3
votes
0answers
72 views
Turning OFF the grill when the espresso maker is ON
These are the variables to this problem:
We have two 120 volt appliances:
- an espresso machine (draws 8 amps)
- and a grill (draws 12 amps).
The grill is ON all the time (it actually stops heating ...
2
votes
1answer
96 views
Analysis of Shunt Circuit
I am having trouble computing the closed loop gain of the circuit below:
It seems clear that this configuration is a Shunt Voltage but I just can't figure a way of computing the feedback factor and ...
0
votes
1answer
113 views
What voltage is put across the Tx+, Tx-, Rx+, and Rx- lines over ethernet?
I'm trying to figure out how to wire up an LED, probably controlled by a FET, for an activity indicator for ethernet. I'm not trying to make one that supports official error codes or anything, but ...
6
votes
6answers
426 views
Basic Electronics - I want to learn the “why”, not just the “how” [closed]
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
139 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 ...
5
votes
2answers
98 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
141 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
257 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.
...
0
votes
0answers
72 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:
...
4
votes
3answers
160 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
85 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
93 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
59 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
122 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
156 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
103 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
52 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
79 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
73 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
196 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 ...
0
votes
1answer
98 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 ...
0
votes
3answers
93 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
350 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
82 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
149 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 ...
