2N5786 vs BD550
| Part Number |
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| Category | Transistors - Bipolar (BJT) - Single | Transistors - Bipolar (BJT) - Single |
| Manufacturer | Harris Corporation | Harris Corporation |
| Description | SMALL SIGNAL BIPOLAR TRANSISTOR | NPN POWER TRANSISTOR |
| Package | Bulk | Bulk |
| Series | - | - |
| Operating Temperature | - | - |
| Mounting Type | - | - |
| Package / Case | - | - |
| Supplier Device Package | - | - |
| Power - Max | - | - |
| Transistor Type | - | - |
| Current - Collector (Ic) (Max) | - | - |
| Voltage - Collector Emitter Breakdown (Max) | - | - |
| Vce Saturation (Max) @ Ib, Ic | - | - |
| Current - Collector Cutoff (Max) | - | - |
| DC Current Gain (hFE) (Min) @ Ic, Vce | - | - |
| Frequency - Transition | - | - |
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1. What is a bipolar transistor?
A bipolar transistor, or bipolar junction transistor (BJT), is an electronic device with three terminals, consisting of three semiconductors with different doping levels. It was successfully developed by William Shockley, John Bardeen and Walter Brattain of Bell Labs in 1947, marking the birth of semiconductor device technology.
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2. What is the difference between bipolar transistors and CMOS transistors?
The main differences between bipolar transistors and CMOS transistors are in working principles, structures, application scenarios, and power consumption.
Working principle
Bipolar transistor: Bipolar transistors have two types of carriers (holes and electrons) involved in conduction, and they are made of three parts of semiconductors with different doping levels. In bipolar transistors, the emitter emits free electrons, the collector receives holes, and the base controls the on and off of the current.
CMOS transistor: CMOS transistors have only one type of carrier (electrons or holes) involved in conduction, usually using a combination of P-type semiconductors and N-type semiconductors. In CMOS transistors, when the gate voltage is zero, the current does not flow. Only when the gate voltage reaches a certain value, the current will flow, which makes the CMOS transistor consume almost no power when static.
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3. Are bipolar transistors still in use?
Bipolar transistors are still in use and play an important role in many fields. Bipolar transistors, the full name of which is bipolar junction transistor (BJT), commonly known as triode, are electronic devices with three terminals, made of three parts of semiconductors with different doping levels. Its working principle involves the flow of two carriers, electrons and holes, so it is called bipolar.
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4. What are the two types of BJT transistors?
There are two main types of BJT transistors: NPN and PNP.
NPN transistor
In an NPN transistor, current flows from the collector to the emitter. The base of an NPN transistor must be connected to a positive voltage for current to flow in. As the current flowing to the base increases, the transistor gradually turns on until the current is completely conducted from the collector to the emitter.
PNP Transistor
In a PNP transistor, the current flows from the emitter to the collector. Therefore, the base of the PNP transistor must be grounded. When the output current is small and the base is negative relative to the emitter, the transistor will turn on and a larger current will flow from the emitter to the collector. Basically, if the base and collector are negative relative to the emitter, the PNP transistor will conduct current from the emitter to the collector.

