The Brief Introduction and Function of Darlington Circuit

The connection method of two transistors as shown in the below is called Darlington circuit. The amplification coefficient is the product of two transistors’ amplifier coefficient.

The definition of Darlington pipe

Darlington pipe is combined by two triodes using the proper connection to form a new equivalent efficiency triode. This process is also called the compound of transistor, so Darlington pipe could be called composite pipe.  Two methods to composite NPN Darlington pipe has the same result, but they have some differences, as shown in figure:

The function of Darlington

• It is used in high power switch circuit, motor speed, inverter circuits.
• It can drive small relays by using CMOS circuit passes through Darlington pipe to drive high sensitivity relay of the circuit.
• It can drive the LED intelligence display

Intelligence display is controlled by micro computer, using LED display matrix board as the display system. It can be used to display all kinds of words and patterns. The system of line and column drive all can use high beta, high-speed low pressure drop Darlington pipe.

What we should pay attention to is that Darlington pipe internal is constituted by multi pipes and resistors, so when using a multimeter to test, positive and negative resistance of be knot is different with ordinary transistor. For the high frequency Darlington pipe, which is easy to miss judged for bad pipe.