Understanding Biasing
Imagine a p−n junction diode as a one-way valve for water. For the water (current) to flow through, the pressure (potential) on the inlet side (p-side) must be greater than the pressure on the outlet side (n-side).
In physics terms, a diode is forward biased when the electric potential at the p-side (Vp) is strictly greater than the electric potential at the n-side (Vn). Mathematically, this is written as:
If Vp<Vn, the diode is reverse biased and acts like a closed valve, blocking the current. If Vp=Vn, there is no potential difference, and the diode is unbiased.
Analyzing the Options
Let's evaluate each option by comparing the potentials at the p-side and n-side.
Option (a):
The
p-side is connected to
+2 V and the
n-side is connected to
−2 V.
+2 V>−2 V
Since
Vp>Vn, this diode is
forward biased.
Option (b):
The
p-side is connected to
−3 V and the
n-side is connected to
−3 V.
−3 V=−3 V
Since
Vp=Vn, this diode is unbiased.
Option (c):
The
p-side is connected to
2 V and the
n-side is connected to
4 V.
2 V<4 V
Since
Vp<Vn, this diode is reverse biased.
Option (d):
The
p-side is connected to
−2 V and the
n-side is connected to
+2 V.
−2 V<+2 V
Since
Vp<Vn, this diode is reverse biased.
The Final Verdict
After carefully checking the potentials for all the given circuits, only the first circuit satisfies the condition for forward biasing. Therefore, the correct option is (a).