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)

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1answer
20 views

Reducing transistor switching time with a resistor from base to a negative voltage

Connecting a resistor from the base of a transistor to ground/negative voltage (R in the first scheme below) helps reduce its switching time. I would like to know why and how does it help; what are ...
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0answers
37 views

Simple output stage for a voltage output audio DAC

I am trying to design a simple output stage for a voltage-out audio DAC. The DAC has an differential output. In the following image VOUTP is the non-inverted output and VOUTN is the inverted output, ...
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0answers
39 views

Solve Questions on full electrical syllabus and help me out its life [on hold]

Please solve these questions and give complete answers. Thank You
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2answers
65 views

need help analysing this BJT circuit

I need help analysing this BJT circuit. What I need to find is the equation for IB, IC, and VCE for this circuit. So far what I've got is from KCL : a: I1=Ib+Ic b: Ie=Ib+Ic So I find that I1=Ie, and ...
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1answer
32 views

eliminitaing spikes from the circuit input

Suppose I have a circuit which gets damaged for spikes and high voltages, so that I need to eliminate spikes and high voltages beyond a maximum value, so I have decided for the following two ...
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0answers
124 views

How to sense current with transistor based design?

I am planning to build a differential amplifier for current sense purpose of microcontroller's ADC. Single ended CM amplifier should provide 3.3 V output to the ADC pin. 3.3 V, 5.2 V, and 3.7 V are ...
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2answers
70 views

faster alternative to 2N3904 [on hold]

Can anyone recommend a "general purpose" small-signal BJT NPN transistor that is similar in most regards to 2N3904, but has a higher fT? The 2N3904 has a fT around 300 MHz, but I'd like something in ...
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1answer
39 views

Changing the path of a signal through multiple transistors with a single-poled switch

I was wanting to construct a "fuzz" distortion guitar pedal, but being indecisive, I wanted to be able to change the type of transistors in the circuit at will. I found the idea of using a ...
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1answer
61 views

I need helping understanding this VCO circuit

The two circuits of interest are described in pages 12-14 of Texas Instruments' Application Note 263, Sine Wave Generation Techniques PDF WARNING I'm primarily concerned about the circuit in Fig. 15, ...
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0answers
43 views

Designing a booster with specific properties [closed]

I've been tasked to design a booster with voltage gain of 150 and input resistance of 100k and output resistance of 50 ohms. I know It's not really right to ask here, but I can really use your help ...
0
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3answers
92 views

what exactly is biasing in transistors and how to do biasing

I have read that collector, emitter must be reverse biased in CE configuration in npn transistor but how can n and n be reverse biased
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1answer
61 views

Transistor count in NAND or NOR implementation of boolean algebra?

I have a complex output function in boolean algebra ( Where '~' means NOT): F=~( (a c ~d) + (a ~c ~d) + (~a c) + (~ a c d) + (a c ! d b) ) I know this can be simplified down to: F = (~a ~c) + (a d) ...
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1answer
51 views

Help With Simulating Common Collector Amplifier In PSPICE

I have included as much information as possible, so it should just be a matter of pointing out something simple (hopefully). I am trying to model a biasing circuit for a Common Collector BJT ...
1
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2answers
72 views

How can I add sounds to my logic probe?

I am a beginner at electronics and I want to build a simple logic probe for TTL circuits. I found this diagram online: Which does exactly what I want. However, I would like to make it play a high ...
1
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2answers
146 views

Choosing the right transistor for a switch

Based on a very closely related question: Choosing the right transistor for a switching circuit I have managed to create a working circuit, but I need the correct transistor. Some context: I am ...
0
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1answer
74 views

Increase toggling speed of PNP for PWM

I got a shift register which I use to PWM LEDs. Since I multiplex this toggling I noticed some "afterglowing" if the next LED is not active of the same color. (RGB cathode) Multiplexing by the MOSFET ...
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1answer
56 views

Question about Shockley's equation for JFETs

I'm currently studying JFETs (Junction Field Effect Transistors) in Navy school. What I know so far is that in JFETs, \$V_{gs}\$ is reversed biased, creating a depletion zone. What this means in plain ...
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0answers
55 views

PNP and NPN transistor used with ARDUINO how to connect them?

This my circuit. What it does is: measuring pressure with MPX200A sensor and looks if pressure under 3 bar, switches on part 1 on arduino (2 transistors) to run DC motor clockwise. If pressure above ...
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7answers
2k views

Transistor - Why does amplification happen before the transistor and not after?

I know this is a noob question but I just can't find an answer for it on google search results. Well my question is basically this: How come the amplifying occurs before the transistor [red line] ...
2
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2answers
117 views

Can I use a BC547 NPN transistor as a thermometer?

In the article Electronic Thermometers for Brewers Ken Schwartz talks about how to use a 2N4401 to create a diode thermometer: I attempted a similar setup with a BC547 transistor ( BC547 Transistor ...
0
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2answers
102 views

What's the difference between a SRAM cell and a D-Latch?

They both seem identical - they both have an "enable" and a single input. When enable is high, the value stored in the element is set to the input. Are they functionally different in any way? (I know ...
1
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0answers
103 views

How does this circuit with three transistors work?

I don't understand how this circuit works. Its a clap switch circuit with transistors. I would appreciate if someone could explain how the current flows through the circuit and which transistor ...
0
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1answer
72 views

Arduino + transistor to switch PC fan on/off

I have: an Arduino UNO a 12V PC fan with 1.68W rating (140ma). 2n3904 transistor 12V 500ma power supply to connect to Vin. What I would like to do is to simply use a digital output pin on the ...
0
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1answer
88 views

Controlling multiple relays with Arduino

I've tested controlling single 24VDC relay with Arduino by using external power source to power the relay. Now I've set up a board to control several of these relays, but noticed that the Arduino ...
0
votes
1answer
124 views

Using a transistor as a heater

I have the task to build and control 35 heaters, 10 W each. I first thought about using power resistors (like in this datasheet) as heating devices, but they'd need high currents in order to get the ...
0
votes
1answer
62 views

Why is the depletion region formed by minority carriers?

While I was studying about the working of transistors I came across a term called the depletion region which stops the flow of electrons from one place to another. A doubt that came to me was why ...
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0answers
69 views

Capacitors not keeping charge as expected

I have a voltage doubler charge pump that is used to provide voltage over an IR LED for a short pulse, I also have a driver circuit for the LED to sink the right amount of current that I am requiring. ...
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2answers
75 views

MOSFET Saturation

I'm looking at the following circuit diagram Where the given parameters are: $$V_{DD} = 1.8V$$ $$R_D = 8k$$ $$V_{GS} = 0.65V$$ $$V_t=0.4V$$ $$k_n=4ma/V^2$$ I was told to find the DC current I(D). ...
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votes
4answers
139 views

Why is a DC base voltage needed to attain faithful amplification?

I was studying about transistor biasing from an article, http://1drv.ms/1yU8B7C, and I have a question regarding this part: Why should an extra voltage \$V_{BB}\$ be needed when there is already an ...
3
votes
1answer
130 views

Why do all transistor latch circuits (that ive seen) use two transistors?

I am looking at building a transistor latch to control a relay. I don't like soldering, so a few components as possible, especially those pesky transistors. I am looking around at various transistor ...
0
votes
1answer
41 views

empty capacitor indicator + short pulse

circuit idea: // note -> times I specify in further text are symbolic ...
0
votes
0answers
53 views

Audio via transistors

Is it possible to push an audio stream through transistors or a DPST relay? I'm using Arduino to do selection between two audio sources and two destinations, and I've completed the first part which ...
1
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0answers
97 views

PNP BJT as a 'switchable' flyback diode?

I have an automotive ignition coil which I'm using as an ignition source for a project I'm working on. During normal operation, the primary coil current will be interrupted periodically to induce ...
0
votes
1answer
47 views

Current limitation of a power supply by using transistors

DALI standard limits the maximum current as 250mA. I have a 12V source that is capable of supplying more current. I implemented from one of Motorola reference design the below schematics that limits ...
0
votes
1answer
61 views

Photo transistor in parallel

I'm a beginner and trying to figure out how this circuit works (its a simple circuit that glows an LED when dark) : https://www.youtube.com/watch?v=eIGWWKThprI&list=UUhtY6O8Ahw2cz05PS2GhUbg#t=65 ...
0
votes
1answer
56 views

Use Arduino for switch a 12v powered remote control

I've a remote control powered by a 12v battery. I need to switch a button using arduino, can I use directly the digital pin without any relay or transistor? Thanks in advance
1
vote
1answer
121 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 ...
3
votes
2answers
360 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
69 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 ...
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2answers
136 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
98 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
466 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
77 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
57 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
2answers
62 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
102 views

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

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
248 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
72 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 ...
0
votes
1answer
36 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
75 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 ...