Formula Used
The calculator estimates the drift contribution first. It then adds aperture, spreading, contact, substrate, metal, and package terms.
Temperature mobility: mu(T) = mu0 × (Tref / T)m
Drift resistivity: rho = 1 / (q × mu(T) × ND)
Ideal drift specific resistance: Rsp,drift = rho × W
JBS aperture drift term: Rsp,JBS = Rsp,drift / open ratio
Total specific on resistance: Rsp,total = Rsp,JBS + Rsp,spread + Rsp,contact + Rsp,substrate + Rsp,metal
Total device resistance: Ron = Rsp,total / active area + Rpackage
Forward estimate: VF = Vbarrier + I × Ron
Average conduction power: P = I × VF × duty cycle
How to Use This Calculator
- Enter active area in square centimeters.
- Add drift thickness, doping, and reference mobility.
- Set operating temperature and the mobility exponent.
- Enter the Schottky open ratio for the JBS cell layout.
- Add spreading, contact, substrate, metal, and package terms.
- Enter current, barrier voltage, and duty cycle.
- Press Calculate to view the result above the form.
- Use CSV or PDF buttons to save the same calculation.
Example Data Table
| Example |
Area cm2 |
Drift um |
Doping cm-3 |
Current A |
Total Rsp mohm.cm2 |
Total Ron mohm |
Forward V |
| Compact 650 V diode |
0.05 |
6 |
1.2e16 |
6 |
1.204801 |
32.096016 |
1.042576 |
| Balanced 1200 V diode |
0.08 |
10 |
8e15 |
10 |
2.037002 |
33.462525 |
1.184625 |
| High current die |
0.16 |
12 |
6e15 |
20 |
2.869203 |
22.93252 |
1.30865 |
JBS Diode On Resistance Guide
A junction barrier Schottky diode mixes two ideas. It uses a Schottky contact for fast forward current. It also uses p plus regions to shield the barrier during reverse voltage. This calculator focuses on the forward on resistance. It is useful during early device sizing, thermal review, and loss planning.
Why On Resistance Matters
On resistance sets the ohmic part of forward voltage. A smaller value lowers conduction loss. It also reduces heat in rectifiers, converters, chargers, and motor drives. In a vertical diode, the drift region is often the main contributor. Its value depends on thickness, doping, mobility, and active area.
What The Inputs Mean
The drift thickness is the current path length. Doping controls carrier density. Mobility shows how easily electrons move. The Schottky open ratio accounts for blocked area caused by junction grids. Contact, substrate, spreading, and package terms add practical resistance. Temperature changes mobility, so hot operation usually raises resistance.
Interpreting Results
The calculator reports specific on resistance in ohm square centimeters. It also converts that value into device resistance by using active area. Current density is shown for design checks. Voltage drop, conduction power, and energy per pulse help compare operating points. Use these values as estimates, not final datasheet limits.
Design Notes
Higher doping lowers resistance, but it can reduce blocking capability. Thinner drift layers also reduce resistance. Yet thickness must support the target voltage. A larger active area lowers device resistance, but it increases chip size and capacitance. A balanced design considers loss, cost, leakage, surge margin, and thermal limits.
Practical Use
Start with measured or process based values. Then vary one input at a time. Watch how area and temperature change loss. Export the result for reports. Compare several cases before selecting a package or layout. For final design, confirm results with simulation, characterization data, and manufacturer guidance.
Common Mistakes
Do not mix micrometers and centimeters. Keep area units consistent. Use realistic mobility at the chosen temperature. Do not treat package resistance as specific resistance. Avoid judging the diode only by one current point. Pulsed testing may look better than continuous service. Always check heat sinking, reverse rating, surge current, and safe operating margins under real loads.
FAQs
What is a JBS diode?
A JBS diode is a junction barrier Schottky diode. It uses Schottky conduction for low forward loss and junction barriers for stronger reverse blocking behavior.
What does on resistance mean here?
It is the effective resistance during forward conduction. It controls the ohmic part of voltage drop and affects heating at load current.
Why is active area important?
Specific resistance is normalized by area. A larger active area lowers calculated chip resistance, but it can raise cost and capacitance.
Why does temperature change resistance?
Carrier mobility usually falls as temperature rises. Lower mobility increases drift resistivity, so the estimated on resistance becomes higher.
What is Schottky open ratio?
It is the conducting Schottky area fraction after junction grid blocking is considered. Lower open ratio increases effective current path resistance.
Can this replace a datasheet?
No. This is an engineering estimate. Use datasheet curves, measured samples, and device simulations for final qualification.
Why include package resistance?
Bond wires, clips, leads, and terminals add resistance. At high current, those terms can noticeably raise voltage drop and power loss.
What units should I enter?
Use centimeters based units for area and doping, micrometers for drift thickness, kelvin for temperature, and milliohm based units where shown.