Darlington Emitter Follower Calculator
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Reviewed by Calculator Editorial Team
A Darlington emitter follower is a transistor amplifier configuration that combines two transistors to achieve higher current gain and improved performance characteristics. This calculator helps you determine key parameters for Darlington emitter follower circuits.
What is a Darlington Emitter Follower?
A Darlington emitter follower is a transistor amplifier configuration that uses two transistors connected in a common emitter configuration. The output of the first transistor is connected to the base of the second transistor, creating a compound transistor with higher current gain.
Key characteristics of Darlington emitter followers include:
- Higher current gain compared to single transistor configurations
- Improved input impedance
- Better noise performance
- Increased voltage gain
Key Formulas
Current gain (β_total) of a Darlington pair:
β_total = β₁ × β₂
Voltage gain (A_v) of a Darlington emitter follower:
A_v = β_total × (R_C / (R_C + R_E))
How to Use This Calculator
To use the Darlington emitter follower calculator:
- Enter the current gain (β) of the first transistor (β₁)
- Enter the current gain (β) of the second transistor (β₂)
- Enter the collector resistance (R_C) in ohms
- Enter the emitter resistance (R_E) in ohms
- Click "Calculate" to see the results
The calculator will display the total current gain, voltage gain, and provide a chart showing the relationship between these parameters.
Formulas and Assumptions
The calculator uses the following formulas to calculate Darlington emitter follower parameters:
Total Current Gain
β_total = β₁ × β₂
Where:
- β₁ = Current gain of first transistor
- β₂ = Current gain of second transistor
Voltage Gain
A_v = β_total × (R_C / (R_C + R_E))
Where:
- R_C = Collector resistance in ohms
- R_E = Emitter resistance in ohms
Assumptions:
- Transistors are ideal with no leakage currents
- Resistors are linear and temperature-independent
- Small-signal analysis is used
Worked Example
Let's calculate the parameters for a Darlington emitter follower with:
- β₁ = 100
- β₂ = 150
- R_C = 10,000 ohms
- R_E = 2,000 ohms
Calculations
Total current gain (β_total):
β_total = 100 × 150 = 15,000
Voltage gain (A_v):
A_v = 15,000 × (10,000 / (10,000 + 2,000)) = 15,000 × 0.833 ≈ 12,500
This example shows how the Darlington configuration provides significant amplification compared to single transistor configurations.
Frequently Asked Questions
What is the advantage of a Darlington emitter follower?
A Darlington emitter follower provides higher current gain, better input impedance, and improved noise performance compared to single transistor configurations.
How does the current gain of a Darlington pair compare to single transistors?
The total current gain of a Darlington pair is the product of the individual current gains of the two transistors (β_total = β₁ × β₂).
What factors affect the voltage gain of a Darlington emitter follower?
The voltage gain is affected by the total current gain and the ratio of collector resistance to the sum of collector and emitter resistances (A_v = β_total × (R_C / (R_C + R_E))).
Can Darlington emitter followers be used in audio amplifiers?
Yes, Darlington emitter followers are commonly used in audio amplifiers due to their high current gain and good noise performance.