Join 60,000+ competitive exam aspirants
or with email
Your Cart
Subtotal₹0
Total₹0
Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
Join 60,000+ competitive exam aspirants
The base-emitter junction of a transistor is ______.
Reverse bias
wide depletion layer
Low resistance
None
Low resistance
Quick Summary: In a Bipolar Junction Transistor (BJT), the base-emitter (BE) junction is always forward-biased during normal operation. Due to the forward bias, the depletion region narrows significantly, allowing charge carriers to pass through easily, resulting in low electrical resistance.
In a Bipolar Junction Transistor (BJT), the base-emitter (BE) junction is always forward-biased during normal operation. Due to the forward bias, the depletion region narrows significantly, allowing charge carriers to pass through easily, resulting in low electrical resistance.
VBE≈0.7V — typical forward bias voltage for Silicon transistors
Rin=dIBdVBE — input resistance (dynamic resistance)
When a positive voltage is applied to the P-type base (in an NPN transistor) relative to the N-type emitter, the majority carriers are repelled towards the junction. This reduces the barrier potential and the width of the depletion layer, drastically lowering the impedance of the path and facilitating high current flow.
The BE junction acts like a forward-biased diode.
The Collector-Base (CB) junction is typically reverse-biased in active mode.
Low resistance is essential to allow the emitter current to inject charges into the base region.
The input impedance of a common-emitter amplifier is determined by this low BE resistance.
Efficient injection of charge carriers
High transconductance gain
High sensitivity to thermal variations
Requires current limiting resistor to prevent damage
BJT-based switching circuits
Linear amplification in Common Emitter configuration
For Germanium transistors, the forward bias voltage VBE is typically 0.3V.
Option A is incorrect because the BE junction is forward-biased, not reverse-biased.
Option B is incorrect because reverse-biased junctions have wide depletion layers, not forward-biased ones.
C is correct — The base-emitter junction is forward-biased, which creates a narrow depletion region and results in a low resistance path for current.
Always remember the mnemonic: 'BE' (Base-Emitter) is Forward-biased for action (Active mode), and 'CB' (Collector-Base) is Reverse-biased to collect charges.