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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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Upgraded flipflop square wave generator - did I do good?

I've drawn up a simple multi-frequency square wave generator, based on a astable multivibrator circut, with frequency trimmed by the two ganged pots (both 100k) and the range set by a DPDT switch, ...
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39 views

How does current sink help in biasing the differential amplifier?

Here M1 and M2 are differential pairs with analog input. When source resistor is used Rs M1 and M2 when Vgs is less than 0.7 Vt threshold M1 and M2 will be in cut off region and Vo1 and Vo2 will be in ...
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72 views

BJT: Finding Ie and Ib [duplicate]

I am struggling to find out the Value of Ie and Ib here. Ic I have taken to be Vcc/10k. If this is correct I could use Ic/alpha = Ie . I would like to know if this is the case but seems to easy to be ...
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47 views

Relay switch not switching

So I purchased a min 3V relay switch (https://www.digikey.com/products/en?keywords=ADW1103HLW) and am trying to turn it on with a simple transistor setup. The data sheet says I only need about 66.7mA (...
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78 views

Transistors: Quiescent voltage and Active mode

I am struggling to understand two things about this circuit. 1) when input and output terminals are open circuit, why is this assumed to be in active mode? 2)What range can the quiescent output ...
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4answers
127 views

Controlling 12V Magnetic Latch Solenoid with RaspberryPi 3b

As the title says I am trying to control a solenoid with a raspberry pi. I am currently using an npn transistor (will post link with parts at the bottom) however I am having a hard time getting it to ...
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71 views

Is this mosfet stable? Trouble with capacitances

I have the following circuit and I'd like to know about its stability : From what I've learned from basic electronics courses, the first step is to add the parasitic capacitances. I know there is ...
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29 views

Connecting/disconnecting charger with transistor

I have a project powered by a small 12V SLA battery that I would like to keep charged by using a 7W solar charger. My plan is to monitor battery voltage and connect/disconnect the charger as needed by ...
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43 views

Voltage drop on power bench supply for channel being off

If I measure voltage drop between terminals of my bench power supply (spec) I get -15 mV when channel output is turned off. Why it is not reading 0? I believe it's due to internal impedance of the ...
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2answers
96 views

install heatsink on BJT

I am facing the problem with the heat of transistor disturb sensor reading. Here the link refer problem I am using BC548 transistor. It is a bit hot when operating because it disipates power around ...
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40 views

Circuit for high voltage pulses using raspberry pi PWM to drive a piezoelectric actuator

I am trying to engineer a device to separate red blood cells from blood plasma in 100mmx1mm capillary tubes using the raspberry pi GPIO pin PWM feature and a piezoelectric actuator. The pulses ...
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83 views

constant voltage source + constant current source with transistors

I need a "driver circuit" for my amplifier. It consists of a dynamic current source, a constant voltage source and a constant current source like shown below: The constant voltage source should ...
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136 views

Power Amplifier (Darlington) with Power and current limitation

I'm designing a power amplifier and the following circuit is the output stage. My output stage consists of two complementary transistors for both, positive and negative waves but for better ...
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123 views

What is the difference between MOSFET transistor and normal transistor? [closed]

I know this might be a stupid question, but what is the difference between MOSFET transistor and normal transistor? There must be a difference but no one says it, people always talk about them as they ...
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29 views

NMOS limiting circuit for Colpitts oscillator

According to my book, the amplitude of the output sine wave produced by the following Colpitts oscillator should be limited by transistors M1 and M2. We only get a final answer without reasoning and ...
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63 views

Control board powered up with reverse polarity. power transistor blown. Is this repairable? [closed]

My dog chewed through the power cord. I 'repaired' it not paying attention to polarity. It was a 2A, 9V wall wart type power supply. The motherboard is from an elliptical exercise machine. The one ...
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Optocoupler or transistor.. which is good for high load relays using Arduino

I'm a newbie or a beginner with electronic stuffs. I'm trying to switch on/off a 1.5hp water pump using Arduino. I've got a 40 amps solid state relay in which the coil voltage is 12-36v. So for that I'...
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What are the differences between the NTE102/103 and NTE102a/103a Germanium transistors?

SO the NTE102/103(a) complementary transistors are a bit more compact(both are cans but the a ones are smaller and thinner). But I've noticed that in particular, the NTE102 is much more prone to ...
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3answers
85 views

PNP Transistor with low base current

I designed a PCB with the following schematics. simulate this circuit – Schematic created using CircuitLab The circuit uses a MAX6369 external watchdog timer which has an open-drain output(...
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1answer
39 views

How does this high impedance circuit stage work

The current i1 flows through Q3 and current i2 flows through Q4. It looks like D5 is trying to mirror the current flowing through it via Q6. D6 is trying to mirror the current flowing through it in Q5....
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1answer
353 views

Why are the input and the battery connected in a transistor amp?

I'm trying to make a simple boost pedal for my guitar using the simplest schematic I found. I'm wondering why the input is connected to the +9v battery in this schematic through a 430kohm resistance. ...
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68 views

4-20mA current loop - transmit sensor reading

I am working on design loop current transmitter- to transmit reading value from thermocouple sensor using below design. I measured co-junction temperature using NTC instead of RTD. During applying ...
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3answers
75 views

How to use a transistor to drive strings of LEDs from GPIO pins?

This is similar to How to drive a 20mA LED From a 4mA max GPIO Pin except that I need a little more hand-holding in order to understand what is happening. For background, I'm a software engineer and ...
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3answers
69 views

Selecting a transistor - Reading transistor datasheets

I am trying to select a transistor part and figure the actual current calculations in my circuit. I have 30mA of collector (load current). This is the transistor I am choosing for my design : https://...
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1answer
49 views

Push Pull Switch Mode Power Supplies

I am reading this material for understanding the switch mode push pull power supplies. Push Pull Switched Mode Power Supplies I am unable to understand the working though. Can someone provide a ...
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45 views

Understanding Optimization/Realization of the voltage controlled current source

I am unable to make a voltage controlled constant current source. So I am using the following scheme (Sorry for bad sketch drawing): The constant control voltage varies in the range of 0 to 5 V is ...
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1answer
31 views

Speed of monostable circuit

i need to find a time between rising edge of input signal and generating new output state. I dont have a scope so i cant measure Does someone have imagine how fast it is and how the edges looks like?
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Stumped about how this switching circuits system works

I have stumbled upon this circuit from an online electronics course (https://pirateselectronics.teachable.com, chapter "Dual Flash Lights"): The behavior of this system is that both LEDs switch on ...
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3answers
60 views

BJT Active mode - How does it work

I am finding it difficult to understand how exactly this works and would appreciate any help. From my understanding: The emitter base junction has to be in forward bias meaning that Vb is more ...
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2answers
52 views

Op Amp Output Voltage

I have a question about an LM741 op amp IC. I am using the op amp as an comparator (open loop with no feedback), as seen below: When the op amp output is low, the output voltage is still around 1.2v....
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1answer
744 views

What is this substance on board?

So I’m trying to fix my blu-ray player and there are two spots where this beige stuff is. Is this there intentionally, or is this the result of some malfunction? Could someone please explain what it ...
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3answers
128 views

Power amplifier, does this circuit work?

I found that circuit for a power amplifier. Does it work? I want to build one for myself.
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1answer
65 views

Why is one of the transistors in ROM sense amplifier twice the width of the one opposite of him?

The picture is of Sense Amp design of ROM component in which a 'dummy' bit line is used to imitate the current so that the proper information can be derived from the memory cell by comparing the ...
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2answers
103 views

Unable to activate an Nmosfet gate with raspberry pi

So I've been trying to control a motor using a MOSFET transistor, where the gate is controlled by a raspberry pi. My circuit is wired as follow: The diodes represent the raspberry pi ground and gpio ...
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2answers
54 views

Is this a suitable Voltage Regulator to replace an old circuit on my board and is my logic correct?

I have 4 of these 2n3904 transistor setups on my board: A1 -- requires 5v on these 2 connected pins to be enabled. I control this by driving r2 high at 3.3v which should allow 5v to flow through the ...
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1answer
203 views

Mystery component in Selfie Stick? (iPhone)

What is the component inside an iPhone selfie stick? Testing reveals it is not a transistor. We have done some probing of it and come up with the following: The mystery 3-pinned component drops the ...
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1answer
98 views

Finding current through an LED in an amplifier using a BJT

Suppose you have the schematic: My job is to find \$I_{LED} \$ knowing that the impedance of the capacitor in negligible against \$V_s\$. Here's my attempt: I intend to do an AC analysis followed by ...
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79 views

Darlington Transistor TIP142 same type but different values

I have a bunch of Darlington NPN Transistors TIP142 that are removed from two separate identical boards. The 1st one have the TO−218 CASE (left side of the image) and the 2nd the TO−247 CASE (right ...
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4answers
123 views

Circuit to convert 24VAC digital signal to 5V DC digital signal

I am designing a circuit to convert 24VAC signal to 5V DC signal. The 24VAC signal is designed where 24VAC is on and 0VAC is off. The signal needs to be fed to an MCU which is 5V DC. The circuit ...
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2answers
40 views

Can I in any way connect +ve side of my led to uln2083a output pin?If no can I do it with M54562 transistor array?

I had conneced my digital pin of arduino to the uln2803a to drive LED. I want to configure my uln2803a such that i can connect +ve side of the led to the output pin of uln2803a IC.
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1answer
81 views

In an NPN transistor, why doesn't current flow without applying a base voltage?

In an NPN transistor, why isn't a typical C-E voltage sufficient to overcome the internal resistance of NPN junction directly? Since we only need 0.7V to overcome the PN junction from the Base to ...
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4answers
217 views

Constant current source gets heated

I am trying to control some power LEDs using a microcontroller. For this I plan to use a transistor based constant current source to protect the LEDs from getting damaged and PWM on the base of the ...
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1answer
42 views

Controlling the power supply of a bluetooth module via GPIO and a transistor

I want to be able to turn a Bluetooth module on and off via a GPIO pin of a microcontroller. My first approach to realize this with a transistor is shown below. Is this approach correct? If not, how ...
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1answer
66 views

Unity Gain Phase Splitter- Why outputs have different voltages

I’m trying to calculate the values of the biasing resistors for this phase splitter circuit. (I know the actual values of the resistors, but I just wanted to manually work it out). When I made the ...
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2answers
84 views

Better Transistor Inverter Using Ground Signal?

I'm getting close to finishing my brand spanking new gate control design. I sincerely appreciate all the help I've received out here. My latest challenge is to extinguish an LED when a circuit is ...
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2answers
75 views

H Bridge extreme voltage drop

I was trying to implement a H-Bridge circuit but had a lot of failures. I'm not really good with electronics, just some basic knowledge. So I've started by creating an buffer to switch the full ...
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33 views

Dimensioning a “NOT” gate with a bipolar NPN transistor

With the schematic below I am to determine a "NOT" gate the value of Rb to which the circuit acts as such, knowing that the voltages given for the logic levels are: $$0\to V\in[-0.3,0.9]$$ $$1\to V\in[...
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2answers
41 views

Logic Circuit Transistor Resistor Values?

Last week, I posted a problem with a logic circuit (Need Help With Transistor Logic Circuit Design), and Analogkid was kind enough to solve it. However, at the time, I didn't realize I still had a ...
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1answer
106 views

Common collector - bias resistor?

[Original question: CCD output buffer; seemed best to make the transistor part a separate post] Taken from Wikipedia, the circuit in Fig. 1 acts as a common collector (high input impedance - low ...
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3answers
103 views

How to define a microcontroller pin as open collector or open drain?

Source I have understood the fundamental theory of open collector and open drain configuration. But the problem is how to define/make a micro controller's pin as open drain? Can any pin of a micro ...