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Can You reverse bias the base emitter of a BJT transistor?
If the 15V supply comes up before, or stays up after, the 12V supply, the reverse bias will be 15V, and the emitter-base junction will break down for all but a few types of transistor. What are the consequences of such breakdown? If the current is limited, as in your case to no more than 1.5mA, not much.
What do you mean by reverse active in BJT?
In the OFF state, the transistor acts as an open switch, so no current flows through. In the ON state, it acts as a short circuit, so current can flow through uncontrolled. In the ACTIVE region, the transistor does something special. It amplifies.
What happens when forward bias is applied to the base-emitter junction?
When forward bias is applied to the base–emitter junction, the equilibrium between the thermally generated carriers and the repelling electric field of the n-doped emitter depletion region is disturbed. This allows thermally excited electrons (in an NPN; holes in a PNP) to inject from the emitter into the base region.
How is the base current of a bipolar junction transistor controlled?
Bipolar transistors can be considered voltage-controlled devices (fundamentally the collector current is controlled by the base-emitter voltage; the base current could be considered a defect and is controlled by the characteristics of the base-emitter junction and recombination in the base).
How to calculate the base-emitter voltage in an NPN?
So you can calculate the current flowing through Rb/base now. You know beta already, so you can calculate the collector current, therefore the collector emitter voltage. Based on our initial assumption, the transistor is in active mode.
Can a reverse bias be 15V or 12V?
There is, however a practical problem which may occur with your circuit. If the 15V supply comes up before, or stays up after, the 12V supply, the reverse bias will be 15V, and the emitter-base junction will break down for all but a few types of transistor. What are the consequences of such breakdown?
Which is the most important characteristic of a BJT?
In order to distinguish these regimes we have to look at the i-v characteristics of the device. The most important characteristic of the BJT is the plot of the collector current, IC, versus the collector-emitter voltage, VCE, for various values of the base current, IBas shown on the circuit of Figure 6.
Where do high injection effects occur in a bipolar junction transistor?
High injection effects High injection effects occur in a bipolar junction transistor, just like in a p-n diode. Since under forward active bias only the base-emitter diode is forward biased, one only has to explore the high-injection effects of the base-emitter diode.
What is the base doping of a bipolar junction transistor?
Consider a bipolar transistor with a base doping of 10 17 cm -3 and a quasi-neutral base width of 0.2 m m. Calculate the Early voltage and collector current ideality factor given that the base-emitter capacitance and the base-collector capacitance are 0.2 nF and 0.2 pF.
Is it safe to reverse bias a be junction?
The BE junction can be reverse biased, and your PNP will be off. The limit is the BE-junction breakdown voltage, as for any PN junction. As long as you don’t exceed that breakdown voltage, you’ll be safe. The maximum reverse voltage the BE junction can withstand is usually listed in the datasheet in the Absolute Maximum Ratings section.