Nexperia USA Inc. BC857-QR

Overview

BC857-Q from Nexperia is a PNP general-purpose bipolar junction transistor (BJT) in SOT23 (TO-236AB) package, designed for low-voltage switching and linear amplification at ≤100 mA collector current and −45 V V_CEO. It delivers DC current gain (h_FE) of 125–800 at V_CE = −5 V, I_C = −2 mA, and is AEC-Q101 qualified for automotive body electronics.

For engineers reviewing the BC857-Q datasheet, BC857-Q pinout, BC857-Q application, or BC857-Q equivalent, this device serves as a drop-in replacement for legacy BC847-Q NPN pairs in complementary bias networks, supports rail-to-rail emitter-follower configurations in 5 V/3.3 V logic interfaces, and enables compact load switching in space-constrained PCBs with thermal resistance R_th(j-a) = 500 K/W on FR4.

Technical Context

The BC857-Q operates as a standard PNP BJT with base-controlled current amplification, requiring reverse-biased base-emitter junction (V_EB > 0) for conduction. Its V_(BR)CEO = −45 V and V_(BR)CBO = −50 V define safe blocking limits under open-base and open-emitter conditions respectively.

Thermal performance is specified for FR4 PCB mounting (single-sided, 35 µm Cu), with T_j(max) = 150 °C and P_tot = 250 mW at T_amb ≤ 25 °C. Noise figure is 2–10 dB at I_C = −200 µA, V_CE = −5 V, making it suitable for low-noise preamplifier stages in sensor signal chains.

Key Specifications

Pinout & Package

SOT23 (TO-236AB) plastic surface-mounted package with 3 leads; 1.9 mm × 1.3 mm footprint, 1.1 mm height, and gull-wing lead form for reflow soldering.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP general-purpose transistor applications.

Compared with BC847-Q and MMBT3906, the BC857-Q uniquely combines AEC-Q101 qualification, −45 V V_CEO, and 125–800 h_FE in SOT23-making it the only option among the three qualified for automotive interior modules requiring both reliability and design flexibility.

Availability

BC857-Q is available at Aetrix Electronics and suitable for automotive lighting control, industrial sensor interfaces, consumer appliance sequencing, and medical diagnostic bias networks requiring stable component supply across extended product lifecycles.

Supply support for BC857-Q includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Nexperia is a global semiconductor expert focused on essential efficiency technologies, delivering high-performance, reliable discrete, logic, and MOSFET devices.

The BC857-Q belongs to Nexperia's AEC-Q101-qualified general-purpose transistor family, engineered for robustness in automotive body electronics and industrial control systems where long-term parametric stability is critical.

FAQ

What is the maximum allowable base current for continuous operation?

The absolute maximum peak base current (I_BM) is −200 mA per the limiting values table. For continuous DC operation, base current must be sized so that power dissipation (V_BE(sat) × I_B) remains within the 250 mW total package limit, typically restricting I_B to ≤ −5 mA at I_C = −100 mA to maintain safe junction temperature.

Can BC857-Q replace BC857B-Q in an existing design?

Yes-BC857-Q is the base designation covering all BC857x-Q variants (A/B/C). The BC857B-Q specifically guarantees h_FE = 220–475 at V_CE = −5 V, I_C = −2 mA. Using BC857-Q without suffix implies full-range h_FE (125–800), so designs relying on minimum h_FE ≥ 220 should verify worst-case gain margin with BC857-Q's broader spec.

Is thermal derating required above 25 °C ambient?

Yes-P_tot = 250 mW is rated only at T_amb ≤ 25 °C. Derating follows linear reduction: P_tot = 250 mW − [(T_amb − 25) × 0.5 mW/°C], reaching zero at T_amb = 125 °C. This is based on R_th(j-a) = 500 K/W and T_j(max) = 150 °C, per section 8 of the datasheet.

Does BC857-Q support wave soldering?

Yes-the package outline and soldering section (Fig. 16) specify a dedicated wave soldering footprint (sot023_fw) with 2.8 mm × 4.5 mm pad layout and 1.4 mm lead spacing. Peak temperature must not exceed 260 °C for ≤5 seconds, and board dwell time in molten solder should be limited to prevent delamination per IPC-J-STD-020.