# 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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### 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 ...
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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 ...
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### BJT gain.Width of base region vs collector current

We know that in active region Ic=beta(Ib),so it means that as Ib decreases the Ic should decrease proportionally,but the early effect states that as we increase Vce the width of the base region ...
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### S8050 D331 base resistor calculation

I was trying a basic transistor circuit to understand transistors (LED on the collector without a base limiting resistor ). Now on to the next step, to know where and when to put what values of ...
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### I need to calculate the NPN bjt 2N4401 base resistor

I'm using the transistor (NPN bjt 2N4401) as a switch to light up 20 leds (leds use 2v 20mA) (my power source is 6V). How to calculate the base resistor?