How can I use PNP as a switch?
How can I use PNP as a switch?
For a PNP transistor, the Emitter potential must be positive with respect to the Base. Then the transistor operates as a “single-pole single-throw” (SPST) solid state switch. With a zero signal applied to the Base of the transistor it turns “OFF” acting like an open switch and zero collector current flows.
In which region transistor acts as a switch?
saturation region
Transistor acts as a switch in the saturation region and cutoff region. The emitter-base junction and the collector-base junction is reverse biased in the cutoff region. Both the junctions are forward biased in the saturation region.
How do you trigger a PNP transistor?
To turn on the transistor you need to get the voltage on the base to be 0.7V lower than the emitter, which is 9V – 0.7V = 8.3V. For example, you can now make the LED turn on when it gets dark by using a photoresistor and a standard resistor set up as a voltage divider.
What’s the difference between PNP and NPN transistors?
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). Sometimes the DC current gain of the bipolar transistor is too low to directly switch the load current or voltage, so multiple switching transistors are used.
How is a bipolar transistor used as a switch?
If the circuit uses the Bipolar Transistor as a switch, then the transistor’s biasing, whether NPN or PNP, is designed to operate the transistor on both sides of the previously seen “I-V” characteristic curves. The transistor switch operating areas are referred to as the Saturation Region and the Cut-off Area.
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.
What can a transistor switch be used for?
As well as its high power and voltage switching capabilities, a “Darlington Transistor Switch” has another benefit in its high switching speeds, making it ideal for use in inverter circuits, lighting circuits and DC motor or stepper motor control applications.
