Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [base]

A BJT (bipolar transistor) has three leads: base, collector and emitter. In most cases base is used to control the transistor.

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My teacher said a BJT phototransistor doesn't have a base

But I find it to be absolutely incorrect. How can a BJT transistor even work without a base? Shouldn't a transistor without base be just a semiconductor (PP, NN)? Does there exist some special NASA-army-grade experimental BJT transistor without a…
qwerty12456
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Capacitor in series with transistor base

I am fairly new to electronics and just had a quick question. I saw the following suggestion for a one shot trigger to wake up an ESP from for example a PIR sensor with one shot trigger and to read the data on another pin: I do not understand how…
tlubes
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Voltage follower simulation low base current

I am trying to get a deeper understanding of how transistors actually work so I can design my own circuits around them. Pictured is an LTspice simulation of a simple voltage follower circuit. I do not understand why the transistor base-emitter…
SirStrategic
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No resistor to limit base current in this BJT application?

A manual fan controller in my PC just 'sploded: fair enough, it was about 10 years old, and driving more fans than appropriate. I got around to fix it, and figured I needed to change the BJT, because the one employed is not available anymore…
Jack
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Increasing the forward voltage required of the PNP transistor?

I am a newbie and was reading about the uses of a 555 TIMER. I came across a project to create 40 LED Bicycle Light in Led Circuits. I can understand the diagram and most of the explanation except where it says The high output level of the 555…
Umesh Anna
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Shorting NPN transistor base to ground

What is the normal convention(safe and reliable), should one connect NPN transistor base to ground or should a resistor be used? My logic tells me that in common emitter mode, shorting base to ground turns off transistor so no current flows between…
tarmogr
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How to select a diode for a Baker clamp?

What are the requirements when selecting a diode for a Baker clamp circuit? How does the reverse leakage current of the diode affect the circuit? Can a diode with relatively high reverse leakage current (e.g. in mA range) turn the transistor on…
Microsoft Linux TM
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Why am I getting negative base current in LTSpice simulation?

When I was trying to bias an NPN transistor I noticed that the base current Ib is negative in LTSpice. So for the sake of simplicity I only apply voltage to the base-emitter junction. As you see in the figure above LTSpice shows this current…
user16307
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Calculationg base-resistor between microcontroller and transistor

I'm curious, when connecting my 2N2222 transistor's base to a PWM output pin on my Arduino, I know the Arduino can deliver a maximum of 40mA current. The 2N2222 only requires around 5 to 10 mA on it's base to switch the collector and emitter. Now,…
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Physics of bipolar transistor turn-off

In a class AB follower push pull amplifier output stage* operated open loop and driven from a low impedance source, these are, from top to bottom, the emitter currents of both transistors, their individual and total base currents, and the output…
bobflux
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Fundamental questions about BJT transistors

Take a standard NPN transistor. The doping of each element of the transistor is in the name. This is what is inside the transistor... Source of image: Bipolarer - Transistor, gif The left "slice" of silicon is doped with an impurity which makes it…
Allenph
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maximum collector-emitter voltage in BJTs

I am reading BC817 datasheet. According to the datasheet, maximum collector-emitter voltage at open base condition is 45 V. In typical applications we don't use open base configuration. My question is that how can I find maximum collector-emitter…
user15847
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Circuit with Base of Transistor connected to ground

I am having troubles understanding a circuit where to base of a transistor is connected to the ground. As far as I know a transistor needs a certain voltage on the base so electricity can flow from the collector to the emitter. However, if the base…
pls_help
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Negative base current

I am designing a flyback driver using a salvaged power transistor that was originally the driver transistor of a flyback in a ctr screen. This power transistor is the 2SC5681 I want to drive this transistor with an IC, and the high base current…
Maxime Loiseau
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Mixing down to base band

What exactly is the base band? I always thought that it is a synonym to intermediate frequency but it appears not to be the case. For example I have Bluetooth signals in the range of 2.4 to 2.48 GHz. What does it mean to mix it down to the base…
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