Darlington Transistors

Definition: A Darlington transistor (or Darlington pair) is a configuration of two bipolar transistors connected in such a way that the current amplified by the first transistor is further amplified by the second one.

Key Features:

• • Very high current gain (β = β₁ × β₂)
• • High input impedance
• • Low output impedance
• • Single package integration (e.g., MPSA14, TIP120)

Typical Applications:

• • Power regulators
• • Motor drivers
• • Amplifier stages
• • Touch-sensitive switches

Pinout (Common TO-92 or TO-220):

• Base (B) – Control input
• Emitter (E) – Output terminal
• Collector (C) – Connected to load

Note: ~0.6V × 2 = 1.2V base-emitter voltage drop due to two PN junctions.