When does a transistor act as a switch?
The transistor operates as a Single Pole Single Throw (SPST) solid state switch. When a zero input signal applied to the base of the transistor, it acts as an open switch.
How is a bipolar junction transistor a switch?
The Bipolar Junction Transistor (BJT) as a Switch 1 (a) mechanical switch, (b) NPN transistor switch, (c) PNP transistor switch. 2 Transistor: (a) cutoff, lamp off; (b) saturated, lamp on. 3 Solar cell serves as light sensor. 4 Amplified microphone signal is rectified to DC to bias the base of the transistor providing a larger collector current.
Which is the SMD version of the bd131 transistor?
The 2SD1626 (SOT-89) is the SMD version of the BD131 transistor. Replacement and Equivalent for BD131
What is the base current of a silicon transistor?
For silicon transistor, V BE = 0.7 V Therefore, as the base current is greater than 56.8 micro ampere current, the transistor will be driven to saturation i.e., it is fully ON, when 5V is applied at the input. Thus, the output at the collector becomes approximately zero.
How is the cut off region of a transistor used?
Cut off region is also known as fully OFF mode. In this mode, it acts as an open switch. To operate the device in cut off mode, We should connect reverse biasing voltage to both junctions. Therefore, in this operating condition, the current can not flow between the collector and emitter terminal due to open circuit between these terminals.
How does a PNP transistor work as a switch?
The Emitter potential must be positive with respect to the Base for a PNP transistor. The transistor then acts as a solid state switch “single-pole single-throw” (SPST). It turns “OFF” acting like an open switch and zero collector current flows with a zero signal applied to the transistor base.
How is a transistor biased in the saturation region?
Therefore, the transistor is completely in OFF condition. Similarly, in the saturation region, a transistor is biased in such a way that maximum base current is applied that results in maximum collector current and minimum collector-emitter voltage.
What’s the difference between a transistor and a NPN switch?
The equations for calculating the Base resistance, Collector current and voltages are exactly the same as for the previous NPN transistor switch. The difference this time is that we are switching power with a PNP transistor (sourcing current) instead of switching ground with an NPN transistor (sinking current).
What is the saturation region of a PNP transistor?
Then we can define the “saturation region” or “ON mode” when using a bipolar transistor as a switch as being, both junctions forward biased, V B > 0.7v and I C = Maximum. For a PNP transistor, the Emitter potential must be positive with respect to the Base.
How is a transistor used as an AC signal amplifier?
When used as an AC signal amplifier, the transistors Base biasing voltage is applied in such a way that it always operates within its “active” region, that is the linear part of the output characteristics curves are used.