Subthreshold Slope Calculator

Subthreshold Slope Formula:

\[ S = V_{sb} \times \eta \times \ln(10) \]

Subthreshold Slope (S):

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1. What is Subthreshold Slope?

Subthreshold Slope is a key parameter in MOSFET characterization that describes how quickly the drain current changes with gate voltage in the subthreshold region. It represents the gate voltage required to change the drain current by one decade.

2. How Does the Calculator Work?

The calculator uses the Subthreshold Slope formula:

\[ S = V_{sb} \times \eta \times \ln(10) \]

Where:

\( S \) — Subthreshold Slope (V/dec)
\( V_{sb} \) — Source Body Potential Difference (V)
\( \eta \) — DIBL Coefficient (dimensionless)
\( \ln(10) \) — Natural logarithm of 10 (≈2.302585)

Explanation: The formula calculates the subthreshold slope based on source-body potential difference and the DIBL (Drain-Induced Barrier Lowering) coefficient.

3. Importance of Subthreshold Slope Calculation

Details: Subthreshold slope is crucial for understanding MOSFET switching characteristics, power consumption in digital circuits, and device performance in low-power applications. A steeper subthreshold slope indicates better switching characteristics.

4. Using the Calculator

Tips: Enter source body potential difference in volts and DIBL coefficient (typically around 0.1 for CMOS devices). Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is the typical range for subthreshold slope?
A: For ideal MOSFETs, the theoretical minimum is about 60 mV/dec at room temperature. Practical devices typically range from 60-100 mV/dec.

Q2: How does DIBL coefficient affect subthreshold slope?
A: Higher DIBL coefficients result in larger subthreshold slopes, indicating poorer switching characteristics and increased leakage current.

Q3: Why is ln(10) used in the formula?
A: The natural logarithm of 10 (≈2.302585) converts the slope from natural log scale to decade scale, as subthreshold slope is typically expressed in volts per decade of current change.

Q4: What factors influence the DIBL coefficient?
A: DIBL coefficient depends on device geometry, channel length, oxide thickness, and doping profile. Shorter channel lengths typically result in higher DIBL coefficients.

Q5: How is subthreshold slope measured experimentally?
A: Subthreshold slope is measured by sweeping the gate voltage while monitoring drain current in the subthreshold region and calculating the slope of the log(I_d) vs V_gs curve.