Transistor as a switch
If the circuit uses the BJT transistor as a switch, then the biasing of the transistor, either NPN or PNP is
arranged to operate the transistor at both sides of the I-V characteristics
curves shown below. A transistor can be operated in three modes, active region,
saturation region, and cut-off region. In the active region, the
However,
both the NPN & PNP type bipolar
transistors can be made to operate as “ON/OFF” type solid-state switch by
biasing the transistors Base terminal differently to that for a signal
amplifier.
Solid
state switches are one of the main applications for the use of transistors to
switch a DC output “ON” or “OFF”. Some output devices, such as LED’s only
require a few milliamps at logic level DC voltages and can, therefore, be driven
directly by the output of a logic gate. However, high power devices such as
motors, solenoids or lamps, often require more power than that supplied by an
ordinary logic gate so transistor switches are used.
Comments
Post a Comment