Transistor operation
The chart describes how to test and understand the operation of both NPN and PNP transistors using multimeters. The key content is summarized as follows:
1.Distinguishing the type of transistor (NPN vs PNP)
• NPN Silicon: Base (B) terminals will act as positive (+) terminals. When tested conductivity, current flows from Base to Emitter and Collector.
• PNP Silicon: Base (B) terminals will act as negative (-) terminals when test conduction, current will flow from Emitter and Collector towards Base.
2. Diode Test
The figure shows the meter settings to the Diode Check or Resistance mode:
• Straddling pressure (V _ F): usually silicon transistors have a value of V _ {BE} and V _ {BC} is about 0.6V to 0.7V (in the figure, showing a value of 0.652V).
• Pinout Identification:
• Base (B): is a leg that measures with two other legs and then needles up (or has a numerical value up) both.
• Emitter (E) vs Collector (C): Normally a Base-Emitter (B-E) seam has a resistance or pressure drop, slightly higher than a Base-Collector (B-C) seam.
3. Internal structure and current flow
The schematic below describes the principles of physics:
• NPN: It has a Negative-Positive-Negative structure with electrons (e) as the main conductive carrier.
• PNP: It has a Positive-Negative-Positive structure with Holes as the primary carrier.
• Doping concentration:
• Emitter (E): The densest substance dope (Heavily doped) to deliver carriers.
• Base (B): Thin and minimal substance dope (Lightly doped) to control flow.
• Collector (C): Moderately doped
4. Basic calculation formula
In the red rectangular frame, the relationship of electricity is shown:
• I _ E = I _ C + I _ B: The current at the Emitter leg is equal to the current at the Collector leg combined with the Base.
•\ eta = I _ C / I _ B: (or\ beta / h _ {FE} value) is the current amplification rate of the transistor.
In a nutshell: If you want to check if the transistor is good, measure the base leg with the other leg. If measured and raised about 0.6-0 7V in one direction (switch the measuring cable and do not go up), then the joint is still normal.











































































