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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How do we have a fixed current in this case?

If we are doing a current-to-voltage converter we can use negative feedback on a common-emitter configuration. Using npn transistors would look like so: We are using a fixed current input and it ...
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How many transistors in Y = ((A+B+C).D)' in CMOS?

There is an example for Y = ((A+B+C).D)' in here. How do I know how many transistors it has? For instance NAND and NOR in CMOS both have two transistors, but I don't really know how to count ...
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61 views

Verify that an increase in 8º C will saturate a common emitter

In the Art of Electronics there is an assertion that if a bias is established with 0.5 the supply voltage, the transistor will saturate if the temperate goes up 8ºC. The schematic is the basic one for ...
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Help understanding “unusually talked about” transistor code markings

I am a beginner trying to gain a better understanding of transistor codes. Before posting this, I searched the web looking for answers but I was unsuccessful. Please take a moment to look at the ...
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33 views

Using SMD Component in Eagle

In my design (eagle cad) I have used BC548 PTH transistor. Now I want to change design to use SMD components. I am not getting BC548 SMD component while adding component in schematic (eagle cad).
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72 views

Using transistors with different threshold voltages

I have an idea that requires switching based on one of three input voltages. The basic idea is to have three different circuit behaviours based on three different voltage inputs. I've been doing this ...
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125 views

How exactly does a transistor amplify the input current in CE configuration

I have gone through tons of forum discussions and videos and books but they all explain in terms of mathematical equations that factor the input by a 'larger than 1' number. What happens physically ...
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52 views

Fire Alarm Circuit using transistor

This circuit is working inversely on PCB as compare to Proteus Software. In software, when the temperature increases the buzzer is on. This is the desired output, but on PCB this circuit is working ...
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69 views

Reading car speed sensor (SDV)

I've been trying to interface with my car's info screen, called a TID (Triple Information Display), from Opel. From the factory, there are multiple things attached to this screen, one of those a line ...
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87 views

Blown transistor on control board. Am I correct that it is probably an N-channel MOSFET? (and help identifying)

Please see the image below. I was attempting to hack my espresso machine (my hack was working, then I re-designed the circuit...). Something went wrong, and I believe I blew an SOT23 transistor (Q2 in ...
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87 views

Solving transistor circuits

Solving transistor circuits is becoming very confusing. Is there a model for every topology? For example, I do not quite understand this answer: I thought \$I_{E}\$ and \$I_{C}\$ were almost equal ...
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74 views

AVR to drive 12V 1A motor

I have AVR that needs to drive 12V 1A motor. I always used NPN BJTs (2N2222), but reading the datasheet says the MAX is 1A (which means I cannot use it here). Instead, I willing to use MOSFET. I have ...
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87 views

What's the usage of this type of biasing?

I'm trying to know What's the usage of this type of biasing BJTs. this is the main schematic. I'm talking about these type of biasing: Another question to me is this type of biasing for ...
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55 views

Unsure of why this two-transistor LED flasher circuit isn't working

Over the years, I've been using a RadioShack Electronics Lab and project manuals to learn more about electronics. I cannot understand why one of the projects I built does not work as intended (that ...
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2answers
66 views

Is it possible to create a computer without sequential circuits?

Do computers (or FSMs) absolutely need sequential logic, or can it be done theoretically without? This seems impossible. Any proof of why it's not the case? (Showing that there can be no memory ...
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23 views

What is the meaning of collector current pulse in the datasheet?

Here is the datasheet of a transistor: http://www.adafruit.com/datasheets/TIP120.pdf In maximum ratings, there is a section called "Collector Current (Pulse)". What does that mean in practice? Lets ...
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49 views

Raspberry Pi Intercom, switch using transistor or relay?

I am researching a way of using a Raspberry Pi to act as an Intercom. I already have the intercom system mounted, but it's a very old one and wanna do something to it to be more new technology ...
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69 views

Advantages of a cascode

The diagram of the cascode was taken from "the Art of electronics": simulate this circuit – Schematic created using CircuitLab The claim is that in this configuration they practically ...
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311 views

How Does This NOT Gate Work?

I think this question may have already been answered, in a way... But I am not satisfied. I'm reading this book about creating a NOT gate and it mentions that electricity flow from the collector to ...
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320 views

How not to waste power with digital inputs?

I am trying to make simple gates with n-MOSFETS, yet I'm not sure how to actually do physical gate inputs correctly. At first, I tried this (a single-pole, single-throw switch from +5V to gate). ...
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18 views

ACPL217 minimum forward voltage

my question is about the ACPL-217 Optocoupler, i use it to control P MOSFET transistor. The ACPL-217 work with the following schema: I want to leave the pin 1 anode of the diode not connected in my ...
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2answers
152 views

What it is the maximum “real” current by the collector that can be drawn from ULN2067B

I am building a 5-volt-to-24-volt DC converter using ULN2067B. According to the datasheet this device can support 1.5 A per darlington per collector. Does that mean that all the darlingtons can ...
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115 views

Transistor inversions

Having some trouble with transistor logic. I have an existing circuit with a 3.3V rail and signal rail that is pulled to 0V when asserted, i.e. active low. I ultimately need to control four 12V LED ...
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52 views

4 to 1 multiplexer using BC549 transistor

I would like to know how to make a 4 to 1 multiplexer using BC549 transistors also the it has a function wherein I can select which input or output to send HIGH or LOW just like the 4051 multiplexer.
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444 views

Simple transistor circuit with unconnected gate pin acts strangely

My brother and I were playing around with some new transistors we ordered (2n7000 n-channel MOSFETs), trying to make a simple switching circuit: connect a switch, LED turns on; open the switch, LED ...
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Is there any advantage to biasing a transistor with a zener diode rather than a (resistor-based) voltage divider?

In the figures below, we see two methods of biasing a bipolar transistor: the first uses a voltage divider, and the second employs a zener diode regulator. Since the voltage regulator appears far ...
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23 views

6v switching large load

I'm looking to build a remote firework launcher. I'm using parts from an rc car for the remote, but I need a circuit that can switch a large current (~2-3amps) with 6v. Can I do this with a ...
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43 views

Darlington Transistor Array

I am Making an 8x8 Led Dot Matrix Display following this guide https://www.insidegadgets.com/2010/11/07/fun-with-8x8-led-matrix/ as you can see it requires a "ULN2803A Darlington Array (of ...
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71 views

How would I use a transistor to switch my DSL modem?

I am newbie to electronics and just know a few basics. I want to switch on my DSL modem so it can start with my computer on. I think a transistor connected to USB +5V voltage would be simple and best. ...
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39 views

Single Transistor DC TO AC Circut

I have a question that may be rather difficult to ask and format however I will try. Now I am very new to electronics in general but in my spare time I play around with them a little bit. I have ...
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36 views

How to slightly modify this circuit for a lower charging current?

I have mosfet controlled transistor charger circuit for Li-ion battery as picture below. So when 5V presents on VCHG, the processor(with power management) will control VDRV for a Vgs(VCHG-VDRV) ...
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93 views

Is there any 40mV transistor's threshold value that is available in the market?

Is there any 40mV transistor's threshold value that is available in the market? My UNO arduino only gives 40mV signal. That is very low. We do not want to use an op amp in order to get it high. We ...
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65 views

Controlling pull-up pins from external circuit

I have a circuit with an Arduino controlling a 2-channel, normal-off, opto-isolated relay board, 5V input signals, turning relay ON when the Arduino digital pin is set LOW. The relays are controlled ...
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725 views

Why would a transistor have its base and emitter tied to ground when its collector goes to another base?

OK, calling me an amateur is being polite. But I am trying to learn more about how these circuits work. One example I am learning from is the ZX Spectrum ULA ...
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102 views

Basic transistor switch

I'm just an amatuer working with some electronics at home. I am trying to use an NPN transistor as a switch. 9v on the Emitter, 6v as the control on the Base to activate the switch, and I'm going to ...
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1answer
93 views

Make: Electronics (Experiment 11) LED blinks only once

There is one more question about Experiment 11 from "Make: Electronics" by Charles Platt. The trouble is that my LED blinks only once, when I connect circuit to power source. (I tried 6V, 9V and ...
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3answers
92 views

Optoisolator with EL wire won't turn off, TRIAC works fine. Why?

I'm pretty new to electronics, and I'm making a circuit to control EL wire with a DC logic control signal. Specifically, I would like to blink the EL wire with the output of a 555 timer. My first ...
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33 views

Single sided capacitor discharge

What I am looking to do here is ,after current stops flowing through D1 , I want current for a few moments to operate the transistor . So this is the circuit , current charges up the capacitor and ...
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1answer
58 views

Exceeding Maximum Voltage Rating of a BJT Transistor

I am wondering how the maximum voltage ratings of Vce and Vcb work for BJT transistors. Are they like MOSFETs in the way that the instant the maximum voltage is exceeded, they are damaged/destroyed? ...
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67 views

Transistor active mode

I have been looking on the web but all I found was theory that I couldn't fully understand,nor apply .How can a NPN transistor be switched on in active mode?I would appreciate if you would give a more ...
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24 views

using TSOP4838 in anti-collision line follower

i want to use IR sensors with emitter part ( IR led ) - calibrated with an IC timer to give 38KHZ IR signal - mounted side by side - not face to face like the counter module - to the receiver part ( ...
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35 views

12/15V 500mA Current Limiter for Supercap Charging

Long time reader finally asking for some help. I have a 10F equivalent capacitive load that needs to be charged to 15V. My issue is that I only have a max draw of 500mA at 30V available (seemingly ...
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3answers
189 views

2N3055 Power Supply

Could someone explain how this circuit works and how the output is maintained at 12V? There is very little information on how the circuit works online. I know the 12V output from the 7812 is used ...
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3answers
73 views

Transistor saturation

I am trying to saturate a transistor , a BC547 A , but I am having a hard time figuring out something.What hFE should I use to compute the base and collector current to make it turn on fully? Here is ...
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1answer
96 views

Need help in building a simple circuit using transistor

I am new to EE. I am trying to figure out a circuit. I need to make use of resistors,a BC547 and a LED. I am using a 9V power supply. Can you recommend a circuit schematic that uses only the ...
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1answer
114 views

Why Does the And Gate have Two Transistors on Top?

Wouldn't the left-side part of the diagram function as a nand gate without the two transistors at the beginning? Why are they part of the diagram? Because in the following picture of a nand gate, it's ...
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117 views

Can I use a transistor to switch to battery backup power when main power goes out?

I am putting together a circuitry, and I want the circuit to continue running even after main power goes out. So I was thinking about this idea of using a PNP transistor and a one-way diode to ...
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112 views

NPN Transistor For 3 volt base to switch/control 5 volts

I have a 3 volt microcontroller that I want to control the power to a 5v microcontroller. What transistor can use a 3 volt base and allow 5 volts through the emitter/collectors. What type of NPN ...
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79 views

Feeding 12V Pulse into Microcontroller 5V - Use a Transistor?

I have a 12V Tachometer Pulse Signal From an ignition unit(From the data sheet)...I would like to feed this pulse into a micro-controller to output the speed to a LCD display. I don't have a scope to ...
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81 views

Q: transistor as a variable resistor for oscillator circuits

this is my first question, I want to ask a simple question, I searched but couldn't find proper answer, here is my situation; I want to build frequency generator circuit with op-amp oscillator ...