The BC846 is an industry-standard general-purpose NPN bipolar junction transistor (BJT) housed in a compact SOT-23 surface-mount package. Designed for low-noise, high-voltage switching and linear amplification applications, the BC846 features a high collector-emitter breakdown voltage of 65V, excellent current gain linearity, and fast switching transitions. It is widely used in automotive modules, consumer electronics, audio preamplifier stages, and general microcontroller interface circuits.

Specifications

• Brand / Manufacturer: Nexperia / ON Semiconductor / Diodes Inc. / Industry Standard
• Part Number / Marking: BC846 (Common Markings: 1A, 1B, 1D depending on gain grade)
• Transistor Type: NPN Bipolar Junction Transistor (BJT)
• Collector-Emitter Voltage (V_CEO): 65V
• Collector-Base Voltage (V_CBO): 80V
• Emitter-Base Voltage (V_EBO): 6V
• Continuous Collector Current (I_C): 100mA
• Peak Collector Current (I_CM): 200mA
• DC Current Gain (h_FE): 110 to 800 (BC846A: 110–220, BC846B: 200–450, BC846C: 420–800 @ I_C = 2mA, V_CE = 5V)
• Transition Frequency (f_T): 100 MHz (Minimum) / 250 MHz (Typical)
• Collector-Emitter Saturation Voltage (V_CE(sat)): < 250mV>C = 10mA, I_B = 0.5mA / < 600mV>C = 100mA, I_B = 5mA
• Total Power Dissipation (P_tot): 250mW to 300mW (at T_amb = 25°C)
• Operating Junction Temperature: -65°C to +150°C
• Package / Case: SOT-23 (TO-236AB) Surface Mount (Pin 1: Base, Pin 2: Emitter, Pin 3: Collector)

Features

• High Voltage Rating: Withstands up to 65V across the collector-emitter junction, making it suitable for industrial 24V/48V systems and telecom circuits.
• Low Noise and Clean Signal Amplification: Excellent low-frequency noise figure makes it suitable for low-noise front-end audio preamplifiers and sensitive sensor signal processing.
• High DC Current Gain Linearity: Maintains stable h_FE across a wide range of collector currents, ensuring predictable gain in analog amplification.
• Fast Switching & High Bandwidth: High transition frequency (f_T up to 250MHz) supports high-speed digital logic switching and RF/IF stages.
• SMD Space-Saving SOT-23 Footprint: Compact surface-mount profile enables high-density PCB layouts and automated surface-mount assembly (SMT).

Common Applications

• General-Purpose Switching: Controlling small relays, indicator LEDs, buzzers, and optocouplers from MCU GPIO pins.
• Audio Preamplifier Stages: Low-noise signal amplification for microphone preamps and analog audio mixers.
• Level Shifting & Inversion: Translating digital logic levels between low-voltage microcontrollers (3.3V/5V) and higher supply rails.
• Current Mirror & Reference Circuits: Building matched current sources and active loads in analog circuitry.
• Sensor Interface Buffers: High-impedance buffering for analog sensor nodes and transducer signal lines.

Usage Tips

• Base Current Limiting: Always calculate and insert a suitable base series resistor (R_B) to prevent excessive base current from damaging the base-emitter junction; ensure sufficient base overdrive (I_B ≈ I_C / 10 to I_C / 20) for full saturation switching.
• Base Pull-Down Resistor: Connect a 10kΩ to 100kΩ pull-down resistor from Base to Emitter (GND) to keep the transistor securely switched OFF when the driving microcontroller pin is floating or in high-impedance reset state.
• Inductive Load Protection: When switching inductive devices (such as relays, small solenoids, or coils), always connect a reverse-biased flyback diode across the load to protect the collector against high-voltage inductive spikes.
• Thermal Derating: For continuous collector currents near the 100mA maximum limit, ensure adequate copper trace area is connected to the collector lead to prevent junction overheating beyond rated power dissipation.

Datasheet