Nexperia USA Inc. BC857QASZ

Overview

BC857QAS from Nexperia is a dual PNP general-purpose transistor in a DFN1010B-6 (SOT1216) package, rated for −45 V V_CEO, −100 mA I_C, and AEC-Q101 qualified for automotive use. It integrates two matched PNP transistors for complementary switching or differential amplification in space-constrained PCBs.

For engineers reviewing the BC857QAS datasheet, BC857QAS pinout, BC857QAS application, or BC857QAS equivalent, key selection criteria include its ultra-thin 0.37 mm profile, dual-transistor layout with verified pin mapping, thermal resistance of 357 K/W (per device), and guaranteed h_FE range of 200–450 at −2 mA/−5 V.

Technical Context

This dual PNP device operates as two independent transistors sharing a common thermal path in a monolithic die within a leadless DFN1010B-6 package. Each transistor supports DC current gain (h_FE) from 200 to 450 under −2 mA/−5 V conditions and delivers V_CE(sat) ≤ −300 mV at −100 mA/−5 mA drive.

It meets AEC-Q101 stress test requirements for automotive environments, with T_j up to 150 °C and storage temperature from −65 °C to 150 °C. Thermal resistance from junction to ambient is 357 K/W when mounted on FR4 with standard footprint - critical for thermally dense layouts.

Key Specifications

Pinout & Package

DFN1010B-6 (SOT1216) is a 1.1 mm × 1.0 mm × 0.37 mm leadless, thermally enhanced plastic package with 0.35 mm pitch and exposed thermal pad (not electrically connected). Its low profile enables use in ultra-thin mobile and ADAS modules.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual PNP transistor applications.

Compared with BC857QAS, BC847QAPN offers complementary polarity at identical size but sacrifices PNP matching; MBT3906DW1T1G provides higher current in a larger package without automotive qualification - making BC857QAS optimal for space-limited, AEC-compliant dual-PNP switching.

Availability

BC857QAS is available at Aetrix Electronics and suitable for automotive body control modules, mobile camera flash drivers, industrial sensor signal conditioning, and USB-C power delivery interfaces requiring stable component supply across production lifecycles.

Supply support for BC857QAS 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 and logic devices for automotive, industrial, and mobile markets.

BC857QAS belongs to Nexperia's AEC-Q101-qualified general-purpose transistor family, engineered for miniaturized, thermally efficient switching and amplification in harsh-environment electronics.

FAQ

What is the maximum junction temperature and how does it affect continuous operation?

The BC857QAS has a maximum junction temperature (T_j) of 150 °C. At ambient temperatures above 25 °C, power dissipation must be linearly derated using the per-device R_th(j-a) of 357 K/W. For example, at 85 °C ambient, max allowable P_tot drops to ~175 mW to maintain T_j ≤ 150 °C - verified via FR4 PCB thermal modeling in Nexperia's application note AN10564.

Can BC857QAS replace BC857B in existing SOT23 designs?

No - BC857QAS uses a DFN1010B-6 (SOT1216) package with 0.35 mm pitch and no leads, while BC857B is in SOT23 with 0.95 mm pitch and gull-wing leads. The footprints, solder reflow profiles, and mechanical mounting are incompatible. A redesign of the PCB land pattern and stencil is required for migration.

Is the thermal pad on the DFN1010B-6 package electrically connected?

No - the exposed thermal pad on the underside of the DFN1010B-6 package is not electrically connected to any internal node. It serves only for thermal conduction to the PCB copper plane and must be soldered to a dedicated thermal pad with appropriate solder mask opening per Nexperia's footprint recommendation (Fig. 11, v.3 datasheet).

How does the dual-transistor structure impact noise performance in amplifier configurations?

In differential pair or current mirror configurations, the matched geometry of the two PNP transistors in BC857QAS yields low input-referred noise - confirmed by a typical noise figure of 10 dB at 1 MHz, 0.2 mA, and 2 kΩ source resistance. This enables precision low-noise preamplification in sensor front-ends without external trimming.