1. The Connection: In a Darlington pair, the emitter of the first transistor is connected directly to the base of the second transistor. Both collectors are typically tied together.
2. Identifying the Configuration:
• A
Common Collector (CC) amplifier, also known as an
Emitter Follower, is characterized by high input impedance and high current gain, with the output taken from the emitter.
• Since the output of the first stage (Emitter) goes into the input of the second stage (Base), and the final output is taken from the second Emitter, it is effectively a cascade of two Common Collector stages.
3. Key Advantages:
• Ultra-High Current Gain ($\beta$): The total gain is approximately the product of the two individual gains ($\beta_{total} \approx \beta_1 \times \beta_2$).
• High Input Impedance: Because it's a CC-CC cascade, the input impedance is significantly higher than a standard single-transistor amplifier.
This makes the Darlington pair ideal for applications where a very small signal (like from a sensor) needs to drive a heavy load (like a motor or relay).