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)
-3
votes
2answers
109 views
Circuit building help [on hold]
I'm a Noob at this and have a basic understanding of what relays do and how to use them.
I am putting an Auxiliary gas tank that feeds my factory tank through the filler neck on my truck. It has to ...
-3
votes
0answers
39 views
What MOSFET to use instead od IRF7319 [on hold]
I'm building the same circuit as in this question:
Can I swap an IRF7319 Dual MOSFET for another cheaper one?
but I have no clue about MOSFET parameters. I would like to use THT device preferably. I ...
5
votes
1answer
149 views
Low-side MOSFET: Current seems limited
I'm trying to use a MOSFET, an N-channel (specifically this one), with a gate controlled by an AVR to power on/off a Raspberry Pi (powered through GPIO), I'm using it on the low side. (Both share the ...
4
votes
1answer
99 views
7555 timer replacement
I want to build this circuit but I do not have a 7555 low power timer so wondered if I can use a NE555? Also can I use a 2N2222 trasistor instead of a BC108? I don't want to try and build it without ...
0
votes
0answers
23 views
suitable replacement for irfp240 / 9240
A three-phase motor driver uses irfp240/irfp9240, each phase = three parallel totempoles.
The unit breaks down on low speed, thermal runaway. I can't change the setup (I'd wish for a multiphase ...
-4
votes
0answers
41 views
5) I want a servo which will have a proximity sensor mounted to rotate 90 degress in both directions continuously to scan the surroundings [closed]
5) I want a servo which will have a proximity sensor mounted to rotate 90 degress in both directions continuously to scan the surroundings. What are the signals I should give to the pins of the servo.
...
2
votes
2answers
66 views
Is a C2328 Transistor OK to use instead of a 2N2222?
I have this simple circuit to drive a 5v solenoid. I made it all except that Q1 is a C2328A transistor I pulled out of an old power supply and C2 is a 220uF cap. D1 is just a diode I took out from ...
1
vote
1answer
72 views
Amplitude Modulation Circuit Components
How does one select the values of components used in Amplitude Modulation Circuit (using a Transistor common emitter amplifier circuit)?
The circuit that I designed ends up giving a weird waveform ...
0
votes
0answers
33 views
N-FET vs. NPN Transistor for 3v3 Logic
I'm looking at the datasheet for the MLX90333 3-axis hall effect sensor. Section 16.4 (pg 40) shows the schematic for connecting the device to a microcontroller. The MLX90333 uses a 3-wire variant of ...
7
votes
2answers
193 views
Using a microcontroller to turn on LED strip
I have 60 leds that came in a strip. One meter of the led strip requires:
400 milliamps
12 volts
I want to control these LEDs with micro controller. I'm thinking of using a TIP120 and a ...
13
votes
3answers
184 views
When are BJTs used in common base configuration?
BJTs are mostly used in common emitter, sometimes common collector configuration. I rarely see common base. When would you use a BJT in common base? For instance, what parameters are different from ...
2
votes
1answer
68 views
4
votes
1answer
117 views
Understanding specs of PNP transistor for replacement
I want to replace an ON Semicondutor BC557 PNP transistor with a Multicomp BC557 PNP transistor. It is just for general switching of LEDs. But the specs look different although they are same mode.
...
3
votes
2answers
123 views
Two NPN Transistors in C-E to C-E Series?
Background: Trying to modify a cheap Digital Picture Frame. Since I don't enough enough about it to modify it's firmware, I need to take a more roundabout route. I will be including a msp430 to ...
0
votes
2answers
43 views
What is the main Computer Memory Addressing Mechanism for Semi-Conductor Memory? [duplicate]
Most semiconductor memory is organized into memory cells or bistable flip-flops, each storing one bit (0 or 1).
How exactly are the needed '1's or '0's taken from Memory? What mechanism or algorithm?
...
1
vote
1answer
47 views
PUT Base Resistors Question
simulate this circuit – Schematic created using CircuitLab
I recently began in electronics and I was wondering why a Programmable Uni-junction Transistor needs two resistors "connected" ...
1
vote
2answers
85 views
How to limit base current in transistor when collector current is unknown?
In the followig circuit I am trying to replace a push button with a transistor:
simulate this circuit – Schematic created using CircuitLab
In the schematic SW1 is the push button that ...
0
votes
1answer
72 views
Is it better to study semiconductors before electronics devices? [closed]
In my university I have no semiconductor course to study. They make us begin studying electronics devices right away (Topics in microelectronics by sedra). My question is should I study semiconductors ...
0
votes
2answers
64 views
Help identifying D1047 transistor (pic included)
Who can help me identify this transistor?
It came out of a Chinese micromotor power supply.
Text on top is "D1047 905".
Can I substitute it with other transistor?
1
vote
1answer
87 views
How to driving small motors using packaged NPN darlington drivers from MCU?
I have this basic circuit of how to drive a motor using a 2N2222 transistor and it all makes sense to me.
I found a bunch of cheap ULN2803APG darlington drivers. I am a bit confused on how to wire ...
1
vote
1answer
158 views
8x8x8 Led Cube Driver Circuit
I am going to build 8x8x8 LED cube. Before I do I need to figure out a good driver circuit. I came here because I have very little knowledge about how a lot electronic parts fit together.
So here's ...
1
vote
1answer
93 views
Trying to read calculator key presses into PC via parallax propeller chip
I am trying to do read the key presses from a calculator via a parallax propeller board (it's actually a DefCon 20 badge) into my computer via USB. I want the calculator to remain fully functional as ...
2
votes
1answer
122 views
Realizing logic gates with transistors: AND and OR gate in parallel, trying to understand different behaviours
I am trying to understand and finally realize a logic gate by using transitors. In order to build a "simple" one-bit adder, my first step was to design a circuit that puts an AND-gate and an OR-gate ...
9
votes
3answers
220 views
What does “the resistance looking into” mean?
See this circuit, from Sedra & Smith microelectronics, 6th edition, page 287:
It says that the resistance between the gate and source looking into the source is 1/gm, but that the resistance ...
7
votes
1answer
185 views
Basic transistor wiring
I'm trying to control a stepper motor using transistors to switch the different phases (am I using the correct terminology?) on and off at the correct times. I'm going to use my Raspberry Pi to do ...
2
votes
1answer
106 views
How to calculate current through an H-Bridge
Given the below H-Bridge, how do you calculate the current through the conduction paths? This particular IC, the L298, has a per-bridge limit of 2A - so I know the upper limit.
If I were to place a ...
2
votes
3answers
82 views
Effect of a transistor on a voltage divider? (or vice versa)
I'm learning about transistors and am trying to make a basic circuit that uses a photoresistor as a sensor to turn an LED on and off depending on light conditions (the 150kOhm resistor is where the ...
2
votes
4answers
101 views
How can I electronically sense the state of an LED in another device with an Arduino?
I'm working on a project to integrate an off the shelf garage door monitor with an Arduino. The base station has a pair of LED's that flash in different patterns to indicate the state of the remote ...
1
vote
2answers
105 views
Transistor not giving enough current
I am using a TIP120 Transistor with pwm from my Arduino to fade an led strip. The RGB led strip requires 12 volts and 1.6 amps of current. I bought a 12 V / 2.5 Amp power supply from Radio Shack and ...
-5
votes
1answer
67 views
LED control using GPIO [closed]
I am using an industrial camera that has GPIO ports which I would like to use for turning LED plate off and on. LED runs on 24 V and 350 mA (between 350 mA and 1500 mA but 350 mA would be optimal).
...
4
votes
2answers
120 views
Why are the current directions in the hybrid-pi model for BJT the same for both NPN and PNP?
Here is the hybrid-Pi model:
with Ic and Ib going in, and Ie going out.
The same circuit can be used for both NPN and PNP, the only thing changing being Vbe for NPN and Veb for PNP.
The currents ...
4
votes
1answer
123 views
Choosing transistor for a raspberry pi switch
I'm trying to design a circuit that will control the power to a raspberry pi with a button. The basic usage is:
first button press-> rasp powers up.
second button press-> rasp continues with ...
2
votes
1answer
128 views
2N2222 Base Current Maximum Tolerance [closed]
I have a 2N2222 transistor that I plan to use with an Arduino Uno. My question is how much current can this transistor handle at it's base?
3
votes
5answers
101 views
BJT input connected to another BJT's output and loading effects
Sedra & Smith Microelectronics, example 6.10, page 390. They ask us to analyze a BJT circuit. Here it is:
simulate this circuit – Schematic created using CircuitLab
In the next ...
1
vote
2answers
113 views
Circular momentary switch for rotation
I'm working on a VHS adapter that uses a VHS Cassette casing with some electronics in it. The hardware contains a battery and some sort of IC which I can Not program, it's not a micro controller, it's ...
0
votes
0answers
30 views
measure resistance circuit when I have an lm334
I have a circuit
simulate this circuit – Schematic created using CircuitLab
this circuit without the lm334(current limiter) should produce some kind of voltage on R6 when R5 and R4 are ...
2
votes
3answers
89 views
Different answers when using two different equations to find the same unknown (BJT)
Problem 43, chapter 6 in sedra and smith microelectronics.
simulate this circuit – Schematic created using CircuitLab
We are asked to find the current flowing in R1 and R2 knowing that ...
0
votes
1answer
99 views
I don't understand this question about BJT in Sedra and Smith
Chapter 6, problem 32.
simulate this circuit – Schematic created using CircuitLab
Design the circuit to establish a curent of 1 mA in the emitter and a voltage of -1 V at the collector. ...
-2
votes
0answers
72 views
bjt transistor designing for a particular gain without emitter resistance [closed]
how to design a voltage amplifier from BC547 with a gain of 50 and no emitter resistance, given supplies of 10 volt.
2
votes
2answers
132 views
XOR Gate design problem
I just recently started trying out on electronics engineering, and have built a OR gate, NOT gate and a AND gate using NPN transistors. When building the XOR gate, this is my design:
However, SW2 ...
2
votes
3answers
108 views
Basic help with calculating values for PN2222A LED circuit
I'm gonna be adding an IR LED to my Arduino Uno and I'm trying to wrap my head around the math used to figure out the exact resistor values needed to use a PN2222A transistor to drive the LED.
I know ...
4
votes
3answers
136 views
Resistors within a Darlington transistor
I've been considering replacing a 2N3904 and TIP31C with a TIP102 in one of my circuits (PWM LED dimmer), and have noticed in the TIP102 schematic resistors leading from each of the bases to the ...
-3
votes
2answers
85 views
Instructing the Program Counter (PC) to increment [closed]
I am building an 8bit computer from TTL, in regards to the Program Counter, sometimes I may not want it to increment on each clock pulse, with that in mind, how would I instruct it to increment?
The ...
0
votes
1answer
120 views
PNP switching circuit - How it will be correct?
Following circuit is used as a switch in one my circuits. The collector is connected to the Vcc and emitter is supplying current. Theoretically it is wrong, right? The supply should be connected in ...
-3
votes
1answer
67 views
SAP-1/8 Bit Computer MAR/RAM [closed]
I am looking to develop my own 8 bit computer with a really basic instruction set.
I do not know however what the best IC is to be able to perform this job.
Could I utilise an Arduino to act as the ...
1
vote
4answers
149 views
Transistor circuit to toggle motor on/off not working (Arduino)
I've been trying to create a simple transistor circuit with a 2N3904 that will toggle a geared DC motor on and off without drawing power from the arduino - I've followed the schematic seen in the 2nd ...
-3
votes
1answer
44 views
Transistor biasing [closed]
I have learnt loads about biasing a transistor, but I never managed to understand them. They talk about DC load line, Class A, B, C and various types of biasing. What are they all about and where can ...
-4
votes
2answers
50 views
Transistor configurations [closed]
I often come across circuits saying that the transistors therein are in common collector (or common emitter or common base) configuration. What is all these configurations about and what is their ...
2
votes
1answer
82 views
Parallel->Series switches for capacitor bank, only one charges
Here's my goal: To create a capacitor bank to dump a load in to a load resistor/inductor, pulsed, without using switches and keeping it as isolated as I can from myself.
Here is what I have so far:
...
2
votes
1answer
107 views
Why MOSFET Pinchoff occurs
This question is regard to enhanced n-type MOSFETs. From what I understand, an inversion layer is formed underneath the insulating layer below the gate of the MOSFET when a voltage is applied to the ...
