TRANSISTOR BASE EMITTER COLLECTOR HOW TO
TRANSISTOR BASE EMITTER COLLECTOR SERIES

That is, you can burn-up a 1 Amp transistor with much less than 1A if you are dissipating power. So, you have to be aware of the transitor's power rating as well as it's current rating, and in some cases you need a heatsink. It will dissipate power, and it will heat-up. When you are operating lineraly, the transistor will 'see' voltage and current at the same time. If you reduce base current to the point where you are no longer in saturation, the transistor begins to limit the current. When you are in saturation the load device (and voltage) determines the current. You can use someting to 'linearly' dim an LED. In that case, the transistor is operating 'linearly', not as a switch. Konfigurasi Common Emitter (Emitor Bersama) Konfigurasi common emitter atau emitor bersama adalah salah satu jenis konfigurasi transistor yang paling umumnya digunakan daripada konfigurasi common base ataupun common collector, baik itu untuk keperluan video, audio, penguat frekuensi tinggi dan lain sebagainya. You can use a resistor (or something else) to control the base current, and as long as you are not in saturation, the collector current is proportional to base current (multiplied by the beta).

TRANSISTOR BASE EMITTER COLLECTOR SERIES

Ohms’ Law says you need a ~200 Ohm resistor.Ĭould i potentially use a transistor to limit current that goes on through the emitter to the device? I mean, by placing a correctly valued resistor in series with the base of transistor, to control the saturation current? Now, you can calculate a resistor value that gives you a base current that’s about 1/50th (to 1/20th) of your collector current.Įxample - If you need 1 Amp, and you have 5V into the resistor (4V across the resistor). In fact, you can assume zero B-E voltage, and most of the time it will work, since we are assuming a low beta and providing plenty of base current. The exact voltage (usually) isn’t important, since (in most applications) most of the voltage is dropped across the resistor… A rather large-percentage change in B-E voltage won’t change the voltage across the resistor that much. The base-emitter voltage is around 1V with the transistor turned-on. (Assuming a low beta insures that we alway have enough base current to saturate the transistor.) So, we can design a circuit that works with betas between 20 & 50 and we can be sure it will always work. But since this is a switching application we dont need to know the exact value. The data-sheet will give you the minimum value (and sometimes a “typical” value). Next, I’ll assume the transistor beta (current gain) is around 100. You shouldn’t be thinking in “maximum” values… You need to find an approximate value that will work with the actual current in your circuit.įirst, I’ll assume this is a switching application, and that the emitter is grounded. (You don’t need the transistor’s maximum current rating for the calculation… But, you need to make sure your application doesn’t exceed the device’s maximum rating.) Or the “worst case” or maximum for your application. We do need to know the approximate collector current. ( A lot of engineering has to do with knowing what’s critical and what can be assumed, ignored, or approximated. You need to allow for tolerances anyway, so there is no exact answer. We can make some appoximations & assumptions to simplify the calculations.

TRANSISTOR BASE EMITTER COLLECTOR HOW TO

The collector current is large compared to the base current.So what I really need to know is, how to calculate the max value of the series resistor that I can wire to the base of transistor, to still allow maximum current through collector-emitter? The current flowing by the remaining electrons is known as the collector current I C. Most of the electrons pass the depletion region of a collector-base junction and pass through the collector region. Typically, it is 2-5% of the total emitter current. The base current is very small compared to the emitter current. Hence, most of the electrons will pass the base region and few of them will recombine with the holes.īecause of the recombination, the current will flow through the circuit and this current is known as base current I B. So, it has a few holes to recombine with the electrons. But the base region is very thin and lightly doped. These electrons move further to the base. This current is known as emitter current I E. And because of electrons, the current will start flowing the emitter-base junction. Therefore, electrons start flowing from N-type emitter to a P-type base. In N-type emitter, the majority charge carrier is electrons. The depletion region of the emitter-base region is thin compared to the depletion region of the collector-base junction (Note that the depletion region is a region where no mobile charge carriers are present and it behaves like a barrier that opposes the flow of the current).

Transistor base emitter collector