Tagged Questions

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)

learn more… | top users | synonyms (1)

1
vote
1answer
64 views

Controlling 90 LEDs using one WS2811

I wanted to build a circuit where i would be able to control 90 LED's using one WS2811 and have a total of 60 WS2811. In this circuit I hope to connect 30 LED's per channel, there is no need for me ...
2
votes
2answers
333 views

Does this linear current source driver deliver constant current?

I was reading on LED driver designs, and I have a question about the linear current source driver. In the circuit below, will D1 ever turn off when there is too much current through R2? In other ...
0
votes
1answer
49 views

Replacement of 2N3822 and 2N5640 for a 0-12v adjustable power supply

I'm trying to make an adjustable 0-12v 0-500mA power supply. I'm using the following schematic as a base (I modified the 240Ohm resistor between Vout and Adj of LM317 2, and the RSC resistor): The ...
1
vote
2answers
120 views

Need help understanding simple oscillator circuit

I know this seems like a really basic question, but bear with me. The following circuit diagram is given by one of my old electronics kits: simulate this circuit – Schematic created using ...
0
votes
1answer
86 views

Transistor amplifier circuit for triangular wave

I've made triangular wave oscilator as shown in Fig. 1 and it works perfectly at frequancy 10 kHz with peak voltage +3 Volt to -3 Volt. I intend to generate SPWM. But when I feed this circuit to ...
3
votes
1answer
447 views

Turn 9V device off using 3.3V logic level signal

i'm facing the problem to turn a 9V (battery) powered device OFF using the output of a 3.3V based microcontroller. To do this i already threw together the following circuit (which works - assuming i ...
0
votes
1answer
70 views

Switching between two output voltage

I have a sensor which generates signal in range of 240mV to 940mv. Now, I use amplifier of voltage for my sensor, which generates output signal in range 350mV to 1000mV. I used rail-to-rail ...
2
votes
1answer
46 views

Using a MOSFET or BJT instead of solenoid

I'm trying to convert all relays and solenoids to transistors in a circuit to make it solid state. I have a small (150cc) 12V DC starter motor that is currently turned on by a small transistor turning ...
1
vote
1answer
28 views

Multiplexing problem with Arduino, MAX7219 e BJT

I tested the circuit below with an Arduino UNO, a MAX7219 and BC338. The sketch in Arduino is a chaser, so the leds should turn on in sequence. It consist of 7 segment (A-G) and two Digit (0-1). The ...
1
vote
1answer
54 views

Control 12V LED Strip with 5V from RaspberryPi or Arduino [on hold]

I have a 12V RGB 5050 LED Strip with no controller and I cannot change the color without modifying the circuit. What I want to do is hook it up to my Raspberry Pi or Arduino and control the color and ...
2
votes
2answers
213 views

Reducing transistor switching time

I am currently required to study different ways of reducing the transistor switching time. From what i understand, the two most used methods are speed-up capacitors and Using a negative, non-linear ...
0
votes
1answer
65 views

Why isn't this LM2917 circuit working to turn off a transistor?

It was suggested to me that I should post a new question (original question here: Minimal Hall effect sensor circuit to keep something off after certain RPM achieved). The below schematic is for ...
-4
votes
0answers
46 views

Home made semiconductors and silicon wafer construction [closed]

I would like to fabricate ICs from scratch. I want to use something like a CNC machine that etches onto silicon wafers, and then somehow put it into a dip package. Upon doing some research, I have ...
0
votes
1answer
28 views

Voltage wave form across a DC motor driven by a transistor with pwm

Above is the simple implementation for a DC motor control with pwm. I was expecting to see a square wave with a Vmax when Q1 is ON and zero when Q1 is OFF like the one here: standard pwm But ...
0
votes
0answers
72 views

I guarantee this one will be fun - Need help putting several circuits together into one

So I did my best to annotate the schematic with what I'm trying to do. Where I'm really running into trouble is past the output of the 555. This is basically a control circuit for a camera's ...
0
votes
0answers
34 views

BJT carrier flow when saturated

I would like to know how carriers flow in a bipolar junction transistor when working in saturation mode. Consider Vbb to be 20V. Normally, electrons would flow from the emitter to the base. Then, ...
1
vote
0answers
56 views

Circuit for finding engine RPM using the magneto's coil ground wire

I'm looking to see if there's a solution without using a microcontroller to find the engine RPM (perhaps spark frequency is a better term?) using only the magneto's coil grounding wire. This wire ...
-1
votes
1answer
65 views

What is cut-in voltage of a transistor?

Some literature talk about cut-in voltage but couldn't find a clear explanation.
-6
votes
2answers
79 views

What should be the value for the resistor for this circuit?

Sorry for this silly question but I am not from an electronics background. I am trying to build a very basic circuit with npn transistor to detect a certain water level. I am assuming the resistance ...
2
votes
2answers
90 views

Very long transmission-line design tips

I'm designing a very long transmission line between a master node a some slaves far away connected by a bus where only 3 wires are used: - A DC power supply (24vdc) - B Digital comm - C Ground As ...
0
votes
2answers
48 views

Basic h-bridge motor driver circuit for audio PWM waves with possible negative voltage

I need to control a DC motor with the PWM audio waves coming out of the audio jack of a device. The device will send a positive PWM to drive the motor forward and a negative PWM signal for driving it ...
0
votes
1answer
36 views

Open-circuit Output Voltage of Bipolar Output Stage

In TI's doc Designing With Logic, p. 16, it shows a method to calculate the internal resistance (\$R_{o}\$): using the open-circuit output voltage (\$V_{o}\$) and short-circuit current (\$I_{os}\$). ...
0
votes
1answer
37 views

MAx peak to peak of ES without clipping?

This is an exam problem in which my instructor gave the answers but no work. Any one has an idea of how to solve it;FOM(figure of merit)= 25/125, RL=15 ohms, Rx=250 ohms, r1,r2,vee,vcc, are not given. ...
1
vote
4answers
467 views

Turn a transistor on when any one of nine LEDs is on using an LM3914

I'm wanting to turn a transistor on when any LED from LED2 through LED10 are on with an LM3914 in dot mode. Basically, I want the transistor to be normally off until at least LED2 begins to light ...
0
votes
0answers
25 views

How to determine resistances to bias BJT based on input impedance, output admittance, and beta of the BJT

I have been given this circuit, with a 2N2222A BJT. I know the input impedance of the BJT is \$ h_{ie} = r_{\pi} = 4k\$, I know the output impedance \$ h_{oe} = 1/r_o = 1/100k = 0.01{\mu}S\$ , and I ...
0
votes
1answer
30 views

Why is the signal inverted on a VDB transistor?

I've got a 3904 connected in a voltage divider bias. Probing the input and output I notice that the output signal is inverted. http://imgur.com/PJv0boI Schematic: http://imgur.com/nAIFBW2 Would ...
0
votes
4answers
70 views

How to measure DC Operating Point of a simple transistor circuit

Could someone explain to me how to find the DC Operating point of this circuit? I need to find it by running a simulation and probing the circuit, not solving for it mathematically, and I'm not sure ...
1
vote
1answer
64 views

Microcontroller circuit

I am using a Stellaris EK-LM4F120XL for a project. The project includes an LCD module, servo motor, ultrasonic ranger and a numpad. The LCD, servo and ranger are rated at 5V operating voltage, and the ...
0
votes
1answer
73 views

Make three respective LEDs blink with an LM3914 in dot mode

I'm trying to figure out how to make in the below schematic, LEDs D2, D3, and D4 blink respectively while the LM3914 is in dot mode when their on state occurs. Basically this would act like a warning ...
0
votes
0answers
41 views

Max peak to peak swing across ES without any clipping distortion?

This is an exam problem in which my instructor gave the answers but no work. Any one has an idea of how to solve it;FOM(figure of merit)= 25/125, RL=15 ohms, Rx=250 ohms, r1,r2,vee,vcc, are not given. ...
2
votes
2answers
117 views

Low voltage audio amplifier clips on 8 ohm loads

Exposition time: One could call me a freshman in electronics and I just designed my first little audio amplifier for headphones. (Pocket design, I want to be able to drive 4 headphone pairs from a ...
4
votes
3answers
822 views

Is this a good way to debounce a switch?

There are plenty of debouncing circuits on the internet, but I couldn't really find one that fitted my needs / available parts, so I came up with my own, from what I had. There's nothing special about ...
2
votes
2answers
94 views

Designing a stiff voltage source using an emitter follower

simulate this circuit – Schematic created using CircuitLab I am new to electronics, and I am trying to do Exercise 2.2, page 67 of The Art of Electronics. Use a follower with base ...
0
votes
0answers
90 views

I think I have burnt my 24V DC motor

I had a 24V DC motor connected to a Polulu motor driver which was connected to an arduino uno board. I accidentally connected a power supply instead of a volt-meter to both ends of the motor while in ...
0
votes
2answers
98 views

An Explanation of CMOS Logic

While trying to understand CMOS Logic on Wikipedia for class, I came upon this paragraph which I can't quite wrap my head around on the duality of CMOS: "An important characteristic of a CMOS ...
0
votes
1answer
66 views

Resistance calculation for transistor base

I read this question's answer on calculating the base resistor value for a 2N3904 transistor. I'm in a similar situation however I'm using a TIP3055 to switch a \$V_{CE}\$ of 12V and a \$I_{CE}\$ of ...
1
vote
2answers
105 views

How are microscopic transistors on microchips made?

How is something like a microchip which is already small as it is able to house even smaller transistors in the millions at such a micro-scale? It seems like such a feat for machine to be able to make ...
0
votes
2answers
126 views

How do you control 130-size DC motors with an Arduino (seemingly 20A DC motors)?

I'm a little confused on specifications and limitations here... I have 3 (130-size, I believe) DC motors I'm attempting to control with an Arduino. They are running off of a 7.2V NiMH battery pack, ...
0
votes
3answers
88 views

Need help finding the right transistor for a switching circuit

I have been doing much research to learn about transistors and to find the right resistor/transistor coupling to power a laser driver that I am building. I want to complete the circuit through the ...
2
votes
1answer
89 views

Are the stock transistor models in LTspice accurate at RF?

Just checking, I'm doing some experimenting of small signal RF design in LTspice.
0
votes
2answers
53 views

Commanding numerous motors with one H-Bridge

Is it possible to command more than one motor with an H-bridge like this: Would this work in real life if I replace switches with transistors and command them?
1
vote
2answers
561 views

What to do with transistors I had desoldered from TV

I am a beginner in electronic design and want to learn about transistors. I have an old TV and I decided to de-solder the following transistors. Can you tell me what I can use them for, are they ...
0
votes
1answer
69 views

Switch Vcc to Ground with a control bit

I have a device that is 1 ohm and it consumes 3Amp. I want to run my device in both ways and I have only one voltage supply. I want to switch ground to Vcc and vice versa with a control bit from mcu. ...
0
votes
1answer
104 views

Minimal Hall effect sensor circuit to keep something off after certain RPM achieved

I have a somewhat limited understanding of electronics and circuits. I'm trying to build a circuit that will keep a transistor in an off state after a given threshold of RPM is achieved using a A3144E ...
1
vote
2answers
170 views

Microcontroller PWM to bipolar push-pull amplifier issues. (level shifting)

I'm trying to design a circuit that allows a micro controller (arduino) to control a voltage to a load. The load voltage needs to be bipolar in nature (+- 3 to 5 V) for use in controlling a TEC. My ...
0
votes
1answer
88 views

Toggle transistors with an shiftregister to light up an LED

First of all I'm quit new to electrical engineering. I had it 3 years in class but I didn't do well. So here is what I plan. I got some shift-registers (74HC595) Which I'll set with an arduino mega ...
2
votes
0answers
152 views

Integrated LED + Resistor + Transistor

Most designers when are controlling an LED have to make the same old circuit of Vcc -> Resistor -> LED -> Transistor (you need the transistor in case your ...
0
votes
1answer
66 views

Transistor: Mix both GND

I Googled a little bit about transistors and I figured out I have a general understanding problem. Can I simply connect the emitter of the transistor to the GND of my microcontroller that controls the ...
1
vote
2answers
82 views

Replace mechanical switch with transistor? MOSFET? Relay?

If I have a switch in some consumer electronics that I take apart, and want to replace a mechanical switch with a digitally controlled one, which component should I use? The only problem I see with ...
1
vote
1answer
52 views

LV & HV MOSFETs

What are some of the differences between low voltage and high voltage MOSFETs? Obviously the voltage rating would be higher for HV transistors but is there anything that would always be true/false ...