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Asking about biasing of the emitter alone does not make sense. When you talk about bias, you talk about a junction, such as emitter-base or emitter-collector or base-collector.
In a bipolar junction transistor (BJT) both the emitter-base and emitter-collector need to be forward biased, otherwise you are operating the BJT in cutoff mode.
Certainly, if you intend to operate the BJT as a switch, then reverse bias for emitter-base (actually, zero bias) could well be one of the valid states, corresponding to a cutoff condition for emitter-collector.
However, operation in linear mode, the other normal way to use a BJT, requires that both the emitter-base and the emitter-collector be forward biased. Of course, depending on the ratio of emitter-base to emitter-collector versus hFe, you could also be saturated, which is a non-linear mode, i.e. an on switch.
Wiki User
∙ 12y ago
Wiki User
∙ 11y agothere are two parts of a PN junction diode p=+ve and n=-
when p is connected to +ve terminal it is called forward biased
when n is connected to -ve terminal it is called reverse biased.
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Why the n-jfet is operated with the negative voltage not the positive voltage?
In a JFET the only insulation between the gate and the channel is a reverse biased diode junction, if this junction becomes forward biased then the gate and channel are effectively shorted and the device no longer acts as a transistor (it will act as a forward biased diode instead). In the n-channel JFET, the gate is the P-side of this diode and the channel is the N-side of this diode. To keep this diode reverse biased (and the device operating as a transistor) therefor the gate MUST always be maintained at a voltage more negative than the most negative section of the channel.
Is light emitting diodes emit visible light when forward biased?
It depends on the particular LED. Some of them emit infrared light. But, yes, emission occurs when forward-biased.
Explain the working principal of diode with diagram?
A diode when forward biased will allow the flow of current while reverse biasing will cut off the flow of current. It is the basic building block of any semiconductor.
Describe forward bias of a diode?
When the polarity of the battery is such that electrons are allowed to flow through the diode,then the diode is said to be forward-biased. Conversely, when the battery is "backward" and the diode blocks current, then the diode is said to be reverse-biased. A diode may be thought of as like a switch: "closed" when forward-biased and "open" when reverse-biased.
Why transistor is used as an amplifier?
A transistor acts like a valve or gate that opens and closes, and allows a current to flow. Since the amount of current that flows is controlled by another input, they can be used to make amplifiers. Carbon microphones and vacuum tubes have the same property, and so have also been used to make amplifiers historically.
How is a non-conducting diode biased?
A nonconducting diode is biased in the reversed direction (reverse polarization).
Why semiconductor photo-diodes are reverse biased?
Because if you forward-biased them they would always conduct, even in total darkness.
What are the vi characteristics of ideal diodes?
Zero current flow when reverse biased, zero voltage drop when forward biased.
A transistor is in active region when?
a transistor in active region when emitter junction is forward biased nd collector junction is reverse biased
Why the resistance of forward bias is equals to zero nd resistance of reverse bias is infinite?
the junction is conducting when forward biased, approaching zero resistancethe junction is nonconducting when reverse biased, approaching infinite resistanceneither is exactly zero or infinite
Does reverse biasing an LED for a period of time reduce its forward biased threshold voltage?
yes
An NPN transistor is correctly biased and turned on if the?
If the EBJ is forward baise and the CBJ is reverse baised then the transistor will in the active/forward mode of operation.
Why should a JFET be operated with only reverse bias on the gate?
If the gate-channel junction of a JFET was not reverse biased the JFET would just act as a forward biased diode across that junction and the gate would cease to have any control over the channel conductance. For the same reason in a MOSFET the substrate-source/channel/drain junction must remain reverse biased. The MOSFET could not act as a MOSFET.
What will happen if a diode is connected to capacitor?
the diode when forward biased will conduct and during reverse biased condition(generally doring reverse biased condition ckt is open mens no current flows;when register is connected)current flows but during reverse biased condition 1--for sometimes initially current flows due to discharging of capacitor. 2--then ckt will be having no current
How much voltage appears across a zener diode when it is forward-biased?
That depends on the zener voltage rating:"low voltage" zeners are just a simple single diode, the zener diode"high voltage" zeners contain 2 back to back diodes in one package, the zener diode and an ordinary diode that is reverse biased when the zener diode is forward biased to block forward conduction of the zener and protect it from overcurrent damage if installed backwards by mistakeThus in "low voltage" zeners when forward biased they will have a normal diode drop (e.g. 0.7V), but "high voltage" zeners when "forward biased" they will act open due to the reverse biased blocking/protection diode in series with the zener.
What is the biasing technique in transistor for it to be in active region?
For a transistor to be in active region : Base Emitter junction should be forward biased and Emitter collector junction should be reverse biased.
What is a half-biased diode?
A diode can only be biased in one direction at a time. It is either forward biased, in which case it conducts, or it is reverse biased in which case it does not, unless its reverse breakdown voltage has been reached. Perhaps you are thinking of a half-wave rectifier, where only one diode is used to conduct on alternate half-cycles of the AC input?
