Key relationship
I=(V−Vd)/r for V>Vd; small reverse leakage below0; below threshold forward current approximated0.
Physics · Class 12
Junction bias and diode IV
Forward bias lowers the junction barrier and narrows depletion; reverse bias widens depletion and usually permits only small leakage before breakdown. The threshold drawing is a simplified piecewise approximation.
Open the interactive experiment →Junction bias and diode IV
முன்னோக்குச் சார்பு தடையையும் வெறுமைப் பகுதியையும் குறைக்கும். பின்னோக்குச் சார்பு வெறுமைப் பகுதியை அதிகரிக்கும்.
Key notes, relationships and model limits
Remember
Forward bias lowers the junction barrier and narrows depletion; reverse bias widens depletion and usually permits only small leakage before breakdown. The threshold drawing is a simplified piecewise approximation.
Common trap
A fixed0.7 V threshold is an approximation, not an exact law for every silicon diode.
Model limits
Explicit piecewise teaching IV, not Shockley or breakdown model. Width ratio sqrt(max(0.02,1−V/0.8)) illustrates abrupt-junction depletion change; forward floor prevents a nonphysical negative width.
What you will learn
Connect junction bias, barrier and IV behavior.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
At0.9 V,Vd0.7 V,r300 Ω, the piecewise forward current is0.667 mA.
Why this matters
The model connects junction bias and diode iv with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Reverse bias normally changes depletion width how?
- Narrows it
- Widens it
- Removes the junction
Read the explanation
The applied field adds to the built-in barrier.
Course connection: Class XII Chapter 14. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.