BC856BS,115

The BC856BS,115 from Nexperia is a dual PNP bipolar junction transistor in the compact SOT363 surface-mount package, offering two independent PNP transistors in a space-saving 6-lead configuration. Designed for general-purpose amplification and switching applications, each transistor features a 65V collector-emitter voltage rating and 100mA continuous collector current capability. The high current gain (hFE of 220 typical, ranging from 125 to 500) makes the BC856BS suitable for low-level signal amplification, while the low saturation voltage (200mV max) ensures efficient switching operation. A key advantage of the dual-transistor configuration is the excellent parameter matching between the two transistors, which is particularly beneficial for differential amplifier input stages, current mirrors, and matched pair circuits. With a low noise figure of 4dB typical and 100MHz transition frequency, these transistors deliver good RF and audio performance. The 200mW total power dissipation rating provides adequate thermal margin for most low-power applications. The SOT363 package measures just 2.0mm × 1.25mm × 0.95mm, saving valuable board space in high-density designs. Supplied in 7″ tape-and-reel packaging with 3,000 pieces per reel, the BC856BS is widely used in consumer electronics, telecommunications equipment, industrial control systems, and automotive electronics where reliable, low-cost PNP transistor performance is required.

The BC856BS contains two independent PNP bipolar junction transistors fabricated on the same silicon die and housed in a single SOT363 package. Each PNP transistor consists of three semiconductor regions — an n-type base between two p-type regions (emitter and collector). When the emitter-base junction is forward biased (emitter more positive than base by approximately 0.7V) and the collector-base junction is reverse biased (base more positive than collector), current flows from the emitter to the collector, controlled by the base current. The current gain (β or hFE) is the ratio of collector current to base current — with a typical hFE of 220, a small base current controls a much larger collector current. In the active region (forward-biased EB junction, reverse-biased CB junction), the transistor behaves as a current-controlled current source, suitable for amplification. In saturation (both junctions forward biased), the collector-emitter voltage drops to a low value (VCE(sat) ≤ 200mV), making the transistor act as a closed switch suitable for digital switching and load driving. Because both transistors are fabricated on the same die using identical processes, their electrical parameters (particularly VBE and hFE) are closely matched — a critical requirement for precision circuits like differential amplifiers and current mirrors where matching determines accuracy and thermal stability. The transition frequency (fT = 100MHz typical) indicates the frequency at which the current gain drops to unity, setting the upper limit for useful amplification. The low noise figure makes these transistors suitable for low-level signal preamplification.

Marking: “Wt%” (where % is the lot/batch code) is printed on the SOT363 package top surface. Pin 1 is identified by a beveled corner. The two PNP transistors are completely independent with separate base, emitter, and collector connections — no internal connection exists between the two transistors. For PNP transistors, the emitter is at the highest potential and current flows from emitter to collector when the base is pulled below the emitter voltage.

• Differential Amplifiers: The matched pair configuration is ideal for differential amplifier input stages in op-amps, instrumentation amplifiers, and precision measurement circuits where VBE matching and thermal tracking are critical
• Current Mirrors and Sources: Used to build current mirrors and programmable current sources for biasing circuits, current sources, and active loads in analog IC design
• Audio Preamplification: Suitable for low-level audio signal amplification in microphones, headphone amps, and audio preamps due to low noise and good gain
• Signal Switching: Serves as an analog switch or signal router in communication systems, test equipment, and data acquisition circuits
• Load Driving and Relay Control: Used to drive small relays, LEDs, and other low-current loads where PNP high-side switching is needed
• Consumer Electronics: Found in TVs, audio equipment, DVD players, and home appliances for general signal processing and switching
• Telecommunications: Used in telecom equipment, modems, and networking devices for line driving, signal amplification, and level shifting
• Automotive Electronics: Deployed in automotive body electronics, sensor interfaces, and control modules for various amplification and switching tasks