Questions tagged [transistors]

The transistor is a semiconductor device that can amplify signals and switch power. Most used types are bipolar (BJT, for Bipolar Junction Transistor), UJT (Unijunction transistor) and MOSFET (FET, for Field Effect Transistor)

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I want to make a voltage limiting circuit

I want to make a simple circuit that gives a constant output voltage regardless of tiny fluctuations in the input. Is it possible to make it so that when the input is off, the output is off, but when ...
3 votes
2 answers
155 views

How is a bistable element formed with two inverters and two transistors in a 6T SRAM cell?

I'm trying to figure out how a charge can be stored between two CMOS inverters and two more transistors. I understand how the inverter works, just with a NMOS and PMOS base connected to a common ...
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How are the transistors in motherboard controlled and timed?

I just watched Bullzoid/Actually Hardcore Overclocking's video on how VRMs actually work, and I have a couple questions. In the video, the Bullzoid mentions how the transistors are switched on and off....
3 votes
3 answers
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Voltage measured across transistor and transistor base current don't match calculated values

This is a newbie question regarding my second electrical circuit. I've built a switch on a breadboard using NPN transistor SS8050 and it works though voltage across transistor's collector and emitter ...
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Master-Slave JK Flip Flop toggles on both edges

I'm trying to make a MS JK Flip Flop with Preset and Clear using only transistors(BC547B) and resistors in LTSpiceXVII. I made four 3-input NAND gates for the master flip flop and four 2-input ones ...
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Biasing for complementary common-source stage amplifier

Why does no current flow through \$R_F\$ in the absence of signals in Fig 5.47(b)? This can only happen if \$V_x = V_\text{out}\$. How is that guaranteed??
3 votes
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1.5 to 9 V transistor boost converter issue

I'm working on a small boost circuit to power a 9 V device with one AA battery (power requirement is 9 V ~ 10 mA). My circuit is inspired by the following video - schematic can be seen in the ...
1 vote
1 answer
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Is there anywhere I can download BJT Transistor I-V data?

Is there anywhere I can download some current-voltage data for a bipolar junction transistor? (It doesn't matter that much which one.) To explain further, for a simple BJT circuit we have the ...
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What is the best way (using solid state) to power off lights when another light circuit powers on?

I am trying to build a circuit that will turn off LED license plate (LP) lights with the LED backup (BU) lights come on. The reasoning for this is that the LP lights wash out the reverse camera due to ...
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138 views

Can I use a 700V transistor with a 12V collector and base?

Please forgive any misunderstandings, as I am not an expert on electrical components. I am trying to build the following circuit: I need to be able to run 1.5A through the transistor. Can I use a ...
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Magnetic levitation without any microcontroller

The above image is taken from here. It uses an electromagnet with two sets of windings which have DC current travelling opposite each other to generate eddy currents in the aluminium plate which helps ...
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How would I connect to these ICSP pins and what is the purpose of the transistor?

I have an old tire pressure monitoring system and was hoping the PIC16F886 in it doesn't have the code protect bit set so that I can modify the behavior of it (namely turn off the beeping from it in ...
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What are junctions in a transistor and how does current flow in them?

I want to clarify what "junctions" are in an NPN transistor and how current flows in them. Is the area inside the blue circle considered the "BC" junction? According to wikipedia ...
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1 vote
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Clarifying how a NPN transistor can act as a switch with a LED in a circuit

I'm experimenting with a simple transistor/LED circuit but after reading many articles online I still can't tell if I have a faulty transistor or things are working as expected. Power source = 5V DC ...
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Will these 2 electromagnet produce a 40kg (400N) attractive force?

Dear all, theoretically according to the electromagnet datasheet, it can attract with 20kg force, does that mean if I have 2 of the same electromagnet and if I switch it to different polarity from ...
2 votes
3 answers
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Can an NPN transistor have its base connected to the same power input as the collector?

All the tutorials I have seen on using an NPN transistor as a switch have base and collector attached to two different power inputs with two different resistors: My question is, can the base just be ...
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2 answers
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RLC resonator to produce beautiful sine wave

simulate this circuit – Schematic created using CircuitLab I have read about the RLC tank which can help to resonate a pulse wave of a certain frequency so that it will produce a beautiful sine ...
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2 answers
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Blinking 3 W, 12 V LED not bright [closed]

I am attempting to control the blink of an automotive brake light LED (3 W, 0.22 A @ 12 V found here- https://www.amazon.com/gp/product/B01MY4T4BU) for maximum brightness. I am using an Arduino Nano ...
2 votes
1 answer
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Is this a reasonable way to determine if an optocoupler transistor is operating in the saturated region?

I found myself thinking about some 50, old (20+ years) optocouplers that I have (removed from working equipment, purchased somewhere or other, or I don’t remember where they came from), and began to ...
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Can a transistor be constructed using diodes? [duplicate]

Can a transistor be constructed using diodes? Can we use diodea as a transistor? I have gotten a assignment to give a presentation on this. I’m unable to understand the question and would like help ...
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9 votes
1 answer
529 views

How are emitter and collector different if NPN transistors are shown as being symmetrical

Images of NPN and PNP transistors show 3 pieces of silicon that are next to each other. There are two types of silicon that are either negative or positive. These form a transistor, being NPN if the ...
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Identify the correct code of an SMD transistor used to switch a relay coil

I have a problem with identifying an SMD component that I'm sure is burned and has to be replaced. It should be a transistor used to switch the 24 V coil of a J01A-24-F relay. Input at the supposed ...
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NPN transistor small output voltage

I just learned about measuring the base resistor of a transistor but I think I did something wrong. I wired everything up like this, but when I measure it I only get around 2.7V out of my device. Is ...
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2 votes
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Switching PNP transistor by using an opto-isolator

I have a problem with a circuit as shown below. I want to drive a pump with the Pump_enable signal but no metter how is this signal state - high or low, the Q3 and Q2 tranistors are always on and ...
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3 votes
4 answers
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Will a bipolar transistor have gain, even if the collector has no curent?

I understand that transistors have a gain, which in proportion to the base's current. My question is quite simple: I was wondering if, when the base had a high current (because of gain), it would ...
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1 vote
2 answers
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How to speed up rise time on logic shifter?

I am trying to boost a 3.3V data signal to 5V, and I'm using a logic shifter to achieve that. Basically, I'm trying to drive WS2813 LEDs, and the data line needs something close to Vdd (5V) to read ...
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Identification of component marked "UJ"

This component is near a coil, some capacitors and I think a diode of some kind. I would be grateful if anyone could identify and provide a suitable part number, I have looked on databases without ...
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1 answer
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Awesome magnetic levitation using Arduino

I followed a Youtube video here and it has instructions at here. The concept is easy which is try to levitate a magnet and balance it using Hall-sensor by changing the PWM of the electromagnet to ...
2 votes
0 answers
71 views

Is there a name for this transistor configuration?

The transistor configuration found in the schematic below can be used as the input to an op-amp that can work with a common mode input at or above the high supply rail. For example this configuration ...
2 votes
1 answer
116 views

Drive a coil with an Arduino

I want to drive a coil with a PID controller on an Arduino. I already made it on my computer, so the PID itself is not a problem. The coil has a resistance of a little less than 1 Ω, an inductance of ...
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1 vote
2 answers
51 views

Switch realisation for power converter

I am having trouble understanding this question. From what I derived all four switches seem to have +ve current and +ve voltage for each switching cycle. Apparently, SW1 and SW2 are meant to be ...
1 vote
0 answers
50 views

Driving LED light chain that needs voltage switching

I have some LED party lights with a defect controller. If you power it "+/-", only the odd ones are illuminating, on "-/+" only the even ones. Now I want to drive them using a ...
1 vote
1 answer
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Will the saturation current through one of these NMOS circuits always be greater than the other?

Is there a definitive way to know for all cases if an NMOS would have a greater saturation current if a resistor R is connected to 1) the drain side or 2) the source side? The assumption is that the ...
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5 V to 4 V and a transistor

I don't now much electronics, so I got myself a project to learn more. I have a 5 V source, something needing 4 V to run, and a way to send a HIGH to a transistor to get the 4 V thing running. For ...
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1 answer
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Calculating CMOS threshold voltage

I found this solution in a textbook, and I do not understand how they calculated Vth2 (typo written as 'Vth' at the bottom). More specifically, where does the 2Vm come from? I understand that Ids1 = ...
1 vote
1 answer
60 views

Amplify tiny voltages accurately

Hi all, above is a Schering's Bridge as a capacitance meter. Following the equation below, Rx resistor is fixed, whereas for capacitor Cx can be placed with an unknown value capacitor. R1 will be ...
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1 answer
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Build a inductance or capacitance meter

Hi all, I am trying to understand the working principle of a Inductor or Capacitance meter and these circuit are common. Looking at the diagrams, the quality factor (sensitivity to frequency change) ...
5 votes
2 answers
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How to calculate the resistor values of a transistor circuit?

I am using an MMBT3904 NPN transistor. Let's say VCC = 12 V, RC = 4.7 kΩ, and the output voltage of an I/O port is 3.3 V. Based on this information: IC = 12 V / 4.7 kΩ = 2.55 mA. The hFE of the ...
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Unstable latching circuit

I'm trying to implement a latching circuit for around 4.1V of voltage (LiPo battery). Below is the circuit: The problem is that the circuit is always on as soon as the power is applied (so even ...
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7 votes
4 answers
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Why is there a transformer in a radio receiver?

This circuit is a radio receiver. The above picture is quoted from here and here. My question is in the diagram. It looks like a transformer symbol. Is it even essential? Can't we use a transformer ...
2 votes
2 answers
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Transistor in saturation mode conditions

I have this circuit where the voltage \$V_A = -4.6V\$ is imposed. I made the hypothesis that the transistor is saturated. Then I calculated \$i_B\$ through KVL: $$-2 + R_Ci_E + V_{EBon} + R_Bi_B + V_A ...
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2 answers
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Demodulator circuit design

Below is Triangular Modulation Output of a Triangle input wave Below is weird Modulation Output of a Triangle input wave when it is connected to demodulator The modulator circuit is quoted from Andy ...
6 votes
5 answers
762 views

Transistor working region hypothesis

In the following circuit of a transistor I know that \$V_A = 2.5V\$. How do I know in which zone the transistor is operating? As I understand it, I should make an hypothesis into one of the working ...
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4 answers
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Power supply for remote load

I tried to design power supply circuit myself because no power supply would do for me (or I'm just unaware). My issue is that I have power supply far away from load and there is no way I can shorten ...
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1 answer
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Linear regulator with high voltage and inductor circuit [closed]

This circuit is based on inner circuit design LM317 IC. The circuit takes a voltage reference of 12 VDC and an input of 320 VDC, and should output 12 VDC, which it does, but in the simulation ...
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2 votes
2 answers
166 views

Supply-independent current source

In the given circuit, the resistor defines the current and it is connected at the source of M2 in this circuit. What will happen if it is connected to the source of M1? I don't see any problem, but I ...
0 votes
2 answers
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Thevenin from terminals point of view in transistor circuit

I know (from the textbook) the Thévenin expressions for the circuit from reference terminals b-b' are $$V_{th} = V_{CC}\frac{R_2}{R_2+R_1}, R_{th} = R_1//R_2$$ But ...
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Buffer an input signal while maintaining the same input waveform undistorted

The above shows an amplitude modulated (AM) signal. I was just wondering how can I make the AM waveform have a very low impendence so that it is able to transmit high power. One solution I tried is ...
0 votes
1 answer
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Voltage modulation circuit

I tried to simulate a modulation circuit which uses a comparator, following this video. The output I get at the 1 kΩ resistor is weird; it should be the same shape as the send signal above. May I know ...
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1 answer
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Is it possible to make a 220 VAC to 12 VDC, 5 A transformerless power supply?

I need to make a power supply that takes 220 VAC and outputs 12 VDC and can handle 5 A. Where I live there are no flyback transformers for sale and importing them is a big hassle. I have some ideas ...
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