Current freely flows from collector to emitter. Cut-off — The transistor acts like an open circuit. … Active — The current from collector to emitter is
proportional to the current flowing into the base
. Reverse-Active — Like active mode, the current is proportional to the base current, but it flows in reverse.
What causes the collector current to flow?
During the positive half-cycle of the signal, the base is positive with respect to the emitter and hence the base-emitter junction is forward biased
. This causes a base current and much larger collector current to flow. … When no signal is applied, a DC current I C will flow in the collector circuit due to the battery.
What is the relation between collector current and emitter current?
What is the relationship between the base-emitter and collector-emitter voltages of a bipolar transistor? Generally, the current that flows from the emitter to the collector or vice versa is
the base current times the DC current gain (h
FE
)
. Note, however, that h
FE
varies with the collector-emitter voltage (V
CE
).
How does current flow through NPN?
The NPN transistor is designed to
pass electrons from the emitter to the collector
(so conventional current flows from collector to emitter). The emitter “emits” electrons into the base, which controls the number of electrons the emitter emits. … The transistor is kind of like an electron valve.
How does current flow in PNP transistor?
When a small current flow through the base of the PNP transistor, it turns on. The current in a PNP transistor flows from
the emitter to the collector
. … The electrons in a PNP transistor are taken from the base terminal. The current that enters the base is amplified before it reaches the collector ends.
What is current gain formula?
Current gain is the ratio of the change in the collector current to the change in the emitter current in a transistor. … Now, substitute the value of the change in the emitter current as 5 mA and 0.99 as the current gain in the formula
α=△Ic△Ie
to determine the change in the collector current in the transistor.
How do you calculate emitter current?
Calculate the emitter current, which is the current flowing from the emitter to ground. Use the formula
Ie = (Vbb – Vbe)/[Rb/(Beta + 1) + Re]
where Ie is the variable for the emitter current and Vbe is the base to emitter voltage. Set Vbe to 0.7 volts, which is the standard for most transistor circuits.
Does current flow from emitter to base?
The NPN transistor is designed to pass electrons from the emitter to the collector (so conventional current flows from collector to emitter). …
The base still controls current flow
, but that current flows in the opposite direction — from emitter to collector.
Can current flow backwards through a transistor?
Yes current can flow in both directions
. An NPN transistor backwards is also an NPN. There will still be a reverse beta, however, the backwards NPN transistor won’t work as well as a correctly oriented one will.
How does current flow in BJT?
Charge flow in a BJT is
due to diffusion of charge carriers across a junction between two regions of different charge carrier concentration
. … The electrons in the base are called minority carriers because the base is doped p-type, which makes holes the majority carrier in the base.
Can I use PNP instead of NPN?
Generally, the
PNP transistor can replace NPN
transistors in most electronic circuits, the only difference is the polarities of the voltages, and the directions of the current flow. PNP transistors can also be used as switching devices and an example of a PNP transistor switch is shown below.
Are NPN and PNP transistors interchangeable?
Answer: NPN and PNP transistors are
interchangeable
if you remember one simple rule: A bipolar transistor is essentially two back-to-back diodes with the base being the common connection. … On the left is an NPN (negative-positive-negative) transistor and on the right is a PNP (positive-negative-positive) transistor.
What is NPN vs PNP?
PNP sensors produce a positive output to your industrial
controls input, while NPN sensors produce a negative signal during an “on” state. … NPN, or “sinking” output sensors, work in the opposite way, sinking ground voltage to an input when it’s on.
What is current gain in common emitter configuration?
The current gain for the common-base configuration is defined as
the change in collector current divided by the change in emitter current when the base-to-collector voltage is constant
. Typical common-base current gain in a well-designed bipolar transistor is very close to unity. The most useful amplifier…
Is current gain constant?
The current gain for the common-base configuration is defined as the change in collector current divided by the change in emitter current when
the base-to-collector voltage is constant
.
What is current gain amplifier?
Mathematically, the gain of a current amplifier is
the ratio between the magnitude of current flowing through its output terminals, to the magnitude of current of the input signal
. … It means that there is a 100-fold increase in the magnitude of current of input signal at the output.
