BC517 COMPOUND TRANSISTOR
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The BC517 is a very specific type of Bipolar Junction Transistor (BJT), known as an NPN Darlington pair transistor. It is not a standard transistor like the BC337/BC327, but rather a compound transistor designed for very high current gain.
✨ BC517 Product Detail
Core Function and Type
Type:NPN Darlington Pair Bipolar Junction Transistor (BJT).
Structure: It consists of two NPN transistors connected together in a Darlington configuration inside a single package. The output current of the first transistor is fed into the base of the second, resulting in a multiplicative effect on the current gain.
Function: It is primarily used as a high-gain switch or an audio pre-amplifier, especially in applications where a very small input current needs to control a large output current.
Key Specifications
| Parameter | Typical Value | Description |
| Collector Current (I_C) | 1A | The maximum continuous current the transistor can switch. |
| Collector-Emitter Voltage (V_CE) | 30V | The maximum voltage it can withstand. |
| DC Current Gain (h_FE) | 30,000 (Minimum) | This is the defining feature; the combined gain is extremely high, allowing it to be driven by microcontrollers or very weak signals. |
| Base-Emitter Voltage (V_BE) | approx1.25V | Due to the two PN junctions in series, the turn-on voltage is roughly double that of a standard BJT. |
| Power Dissipation (P_D) | 625mW | the maximum power it can safely dissipate. |
Package and Applications
Package: Like the BC337/BC327, the BC517 is commonly housed in the axial-leaded TO-92 plastic package.
Applications: Its extremely high current gain makes it ideal for:
Microcontroller Interfaces: Directly driving relays, motors, solenoids, or high-power LEDs from a low-current digital output pin.
Sensor Amplification: Amplifying the weak signals from light sensors (like LDRs) or other low-current sensors.
Audio Preamplification: Used in the input stages of audio amplifiers due to its high