Manual

Atlas DCA User Guide October 2007 – Rev 7

Page 11

Bipolar Junction Transistors (BJTs)

Bipolar Junction Transistors are simply “conventional”

transistors, although variants of these do exist such as

Darlingtons, diode protected, resistor shunted types and

combinations of these types. All of these variations are

automatically identified by the

Atlas DCA

Bipolar Junction Transistors are

available in two main types, NPN and

PNP. In this example, the unit has

detected a Silicon PNP transistor.

The unit will determine that the

transistor is Germanium only if the base-

emitter voltage drop is less than 0.4V

and is also PNP.

If the device is a Darlington transistor (two BJTs connected

together), the unit will

display a similar

message to this:

Note that the

Atlas DCA

will determine that the transistor under test is

a Darlington type if the base-emitter voltage drop is greater than

1.00V for devices with a base-emitter shunt resistance of greater than

60k

Ω

or if the base-emitter voltage drop is greater than 0.80V for

devices with a base-emitter shunt resistance of less than 60k

Ω

. The

measured base-emitter voltage drop is displayed as detailed later in

this section.

PNP Silicon

Transistor

PNP Germanium

Transistor

NPN Darlington

Transistor