With such a configuration, therefore, the U-load is powered when a negative voltage is applied to the base. Since the emitter has the same voltage that power supply, the base must be connected to a lower potential: this is the task of the Rb resistor, through which the base current (coming from the positive pole) can flow towards ground. In order for the current to flow trough the user, a negative voltage must be applied to the emitter. In this case the load (or U user) is located between the collector output and the negative pole (i.e. How can we ensure that the transistors are in good condition and failed?.In Figure 3 we see the case of a PNP transistor. With the help of above mentioned steps we can identify NPN and PNP transistor using multimeter. The logic behind this is, in PNP transistorĮmitter (E) - P type material - Equivalent to anode of the diodeīase (B) - N type material - Equivalent to cathode of the diodeĬollector(C) - P type material - Equivalent to anode of the diode It will ensure that it is a PNP transistor.Similarly touch the negative probe to the center pin (Base) with respect to the pin-3 (collector). You will see some voltage in the multimeter.Touch the negative probe to the center pin (Base). You will see some voltage in the multimeter.Keep the positive probe to the pin-1 (Emitter) of the transistor.Steps to identify the PNP type transistor: If the connections are interchanged it will not show any value. If the multimeter positive probe is connected to anode and negative probe is connected to cathode, then it will show voltage.The logic behind this is, in NPN transistorĮmitter (E) - N type material - Equivalent to cathode of the diodeīase (B) - P type material - Equivalent to anode of the diodeĬollector(C) - N type material - Equivalent to cathode of the diode It will ensure that it is a NPN transistor.Similarly touch the negative probe to the pin-3 (collector) with respect to the pin-2. You will see some voltage in the multimeter.Touch the negative probe to the pin-1 (Emitter). You will see some voltage in the multimeter.Keep the positive probe to the center pin (Base) of the transistor.Steps to identify the NPN type transistor: If the multimeter positive probe is connected to the cathode of the diode and the negative probe to the anode, then it will not give any voltage (showing zero).In the diode mode, the multimeter will show the voltage when we keep the positive probe of the multimeter to the anode of the diode and negative probe to the cathode.Ie,Emitter to base is one PN junction ( diode) and Base to collector another PN junction (diode). The transistor internally has two diodes (NPN ≡ N - P - N ≡ NP Junction + PN Junction and PNP ≡ P - N - P ≡ PN Junction + NP Junction).We need a multimeter to identify the type of BJT. The schematic symbol of the BJT is given below: Identifying BJT Types:īoth NPN and PNP transistor looks similar in physical appearance. Now starting from left, mark like 1,2 and 3. Keep the transistor such that the flat surface facing towards you as shown in the below figure: The transistors are available with various packages in the market. We know that the Bipolar junction transistor has three terminals namely In this post, we will discuss about how to find out the NPN and PNP transistor using multimeter.īefore proceeding further, let us refresh about how to identify the transistor terminals. (Almost everyone would have face this problem) Imagine from your component box, you have picked couple of Bipolar Junction Transistors (BJTs) and you don't know whether they are NPN or PNP type transistors. How to Identify NPN and PNP Transistor (BJT) using Multimeter?
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