What Is the BJT Early Voltage & Small-Signal Output Resistance Calculator?
The Early effect is the variation in effective base width in a bipolar transistor caused by changing collector-to-base voltage.
How Does the BJT Early Voltage & Small-Signal Output Resistance Calculator Work?
Higher collector-base reverse bias widens the junction depletion region into the base, narrowing neutral base width.
BJT Early Voltage & Small-Signal Output Resistance Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
r_o = rac{V_A + V_{CE}}{I_C} approx rac{V_A}{I_C}, quad g_o = rac{1}{r_o}
Small-signal dynamic output resistance from Early base-width modulation.
How to Use the BJT Early Voltage & Small-Signal Output Resistance Calculator
- Enter Early voltage V_A, operating collector current I_C, and collector-emitter voltage V_CE.
Step-by-Step Example Calculation
BJT Small-Signal Audio Amplifier Stage
Input Values:
earlyVoltageVaVolts:100
collectorCurrentMa:2
collectorEmitterVoltageVceVolts:5
Worked Steps: Output resistance r_o = 52.5 kΩ with dynamic output conductance g_o = 19.05 µS.
Understanding Your Result
Shows the small-signal collector dynamic output resistance r_o determining intrinsic stage gain A_v = -g_m * r_o.
Factors That Affect the Result
- Heavy base doping reduces depletion encroachment, yielding higher Early voltages and flatter output characteristics.
When Should You Use This Calculator?
- Analog IC current mirror matching, high-gain discrete amplifier design, and SPICE model parameter extraction.
Assumptions & Limitations
- Linear extrapolation model; assumes active forward bias mode.
Frequently Asked Questions
Calculation Accuracy & Reference Note
Standard Gummel-Poon and Ebers-Moll small-signal output resistance model.