PNP is the acronym for Positive, Negative, Positive. Also referred to as sourcing. When undriven, a PNP input on an IO Module is dragged up to a high state, such as +5V. Digital signals are typically NPN or PNP. Sensors are a sample of NPN or PNP devices.
What Does PNP Stand For in Electronics
In a PNP transistor, the current passes from the collector to the emitter. When there is no current at the transistor’s base, the transmitter is turned on. One n-type material is loaded with two p-type materials in a PNP transistor.
It’s a device that’s powered by electricity. The modest quantity of base current regulates both the emitter and collector currents. In the PNP transistor, two crystal diodes are coupled back-to-back.
The Emitter (P-type) is connected to the positive terminal of a voltage source (VEB), and the Base terminal is attached to the negative terminal (N-type). As a result, the Emitter-Base junction is biased forward.
A voltage source’s positive terminal is connected to the Base terminal (N-type), while the negative terminal is connected to the Collector terminal (P-type). As a result, the Collector-Base junction is biased in the opposite direction.
The junction between the emitter and the base is forward-biased. As a result, several holes from the emitter pass the depletion region and reach the Base. Simultaneously, a small number of electrons from the base enter the Emitter and merge with the holes.
As the Base is a very lightly doped and narrow region, the number of electrons in it is quite small. As a result, nearly all Emitter holes will cross the depletion area and penetrate the Base layer. The current will flow via the Emitter-Base connection due to the movement of holes.
The majority of charge carriers in the Emitter current flow through the holes. The remaining holes will proceed to the Collector if they do not merge with electrons in the Base. Due to holes, the Collector current (IC) travels through the Collector-Base area.
PNP switch stands for ‘Switched Positive’. The term “switched” refers to the electrically switched side of the controlled load (relay, tiny indicator, or PLC input). Either the load is linked to negative with the positive switch (PNP), or the load is coupled to positive with the negative switch (NPN).
As they source positive power to the output, PNP sensors are also referred to as “sourcing sensors.” The active high output is provided by PNP proximity sensors. When an object reaches the sensor’s detection range, the sensor’s output is linked to +24V. It identifies this as a logic HIGH signal when linked to a PLC input.
PNP Vs NPN
In a nutshell, the NPN transistor needs a specific current from the base to the emitter, while the PNP transistor requires a negative current from the base to the emitter, but both require current to flow out of the base to the ground.
PNP transistor is NO – normally open, which indicates that when the sensor is not triggered, there is no voltage on the output. We shall have +24 V on connector no. 4 when the sensor is triggered. This +24V signal can be directly connected to a PLC or used for other purposes like relay actuation or alarm actuation.
As proximity sensors have a current limit of up to 200 mA, all schemes state that the output is connected via a resistor. In reality, this resistor is built into your plc, and it may be your relay coil or indication lamp.
We will get a short circuit if we connect the output straight to GND (the minus cable), which means the current will rise until it reaches the maximum current of the power source. If we have a 5A power supply, for example, short-circuiting will surpass the sensor current limit, causing damage.
If we have an NPN NC sensor, it signifies that our sensor has an NPN transistor on the output and is typically closed, which means that the output signal is at a high level even when the sensor is not activated. We’re using the positive cable instead of grounding.
In the area of industrial control, the PNP paradigm has got a spot. In electronics, PNP devices serve a significant value. The transistors, switching, and sensing operations include specific characteristics and mechanisms denoting PNP.