Infineon BC850CE6327: Technical Specifications and Application Circuit Design Guide
The Infineon BC850CE6327 is a general-purpose NPN bipolar junction transistor (BJT) housed in a compact SOT-23 surface-mount package. As a cornerstone component in modern electronic design, it is renowned for its high reliability, excellent amplification capabilities, and versatility across a wide range of applications, from consumer electronics to industrial control systems. This guide provides a detailed overview of its technical specifications and offers practical insights into its circuit design implementation.
Technical Specifications
The BC850CE6327 is part of the BC850 series, which is characterized by its low noise and high current gain. Key electrical parameters define its operational boundaries and performance:
Polarity: NPN
Package: SOT-23
Collector-Emitter Voltage (VCE0): 45 V
Collector-Base Voltage (VCB0): 50 V
Emitter-Base Voltage (VEB0): 5 V
Continuous Collector Current (IC): 100 mA
Total Power Dissipation (Ptot): 250 mW
DC Current Gain (hFE): This is grouped into classes. The BC850C variant typically offers a gain range of 420 to 800 at a collector current of 2 mA and a collector-emitter voltage of 5 V, making it ideal for high-gain amplification stages.
Transition Frequency (fT): 100 MHz (minimum), indicating its suitability for low-frequency and audio frequency applications.
These specifications highlight the transistor's capability to handle moderate voltages and currents while providing significant signal amplification.
Application Circuit Design Guide
The primary functions of the BC850CE6327 are switching and amplification. Below are two fundamental circuit configurations.
1. Common-Emitter Amplifier
This is the most prevalent configuration for voltage amplification. The design involves biasing the transistor to operate in its active region.
Biasing Network: Resistors R1 and R2 form a voltage divider to set a stable base bias voltage. The emitter resistor RE provides DC feedback for thermal stability, preventing the operating point from shifting due to temperature changes.
Gain: The voltage gain (AV) is approximately calculated as AV ≈ - (RC / RE), where RC is the collector resistor. The negative sign denotes a 180-degree phase inversion between the input and output signals.
Coupling Capacitors: CIN and COUT block DC bias voltages from the source and the load, allowing only the AC signal to pass.
2. Low-Side Switch
This circuit is used to control a load (e.g., an LED, relay, or motor) by switching it on and off from ground.
Operation: Applying a sufficient voltage (typically > 0.7V) to the base terminal via a current-limiting resistor (RB) saturates the transistor. In saturation, the voltage between collector and emitter (VCE(sat)) is very low (typically < 0.6V for this device), allowing nearly the full supply voltage to appear across the load, turning it on.
Base Resistor Calculation: The base resistor (RB) is crucial. It must be chosen to provide enough base current (IB) to drive the transistor into saturation: IB > (IC / hFE). A common design rule is to ensure IB is 1/10th of the collector current for hard saturation.
Protection Diode: When driving an inductive load like a relay coil, a flyback diode (D1) is mandatory across the load to protect the transistor from voltage spikes generated when the current is suddenly interrupted.
Design Considerations:
Current Limitations: Always ensure the collector current (IC) remains below the absolute maximum rating of 100 mA.
Power Dissipation: Calculate power dissipation (IC VCE) to ensure it does not exceed 250 mW, considering ambient temperature.
Stability: Use feedback resistors and bypass capacitors where necessary to prevent oscillations, especially in high-gain amplifier stages.
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Keywords:
NPN Transistor
SOT-23 Package
Current Gain
Common-Emitter Amplifier
Low-Side Switch
