Diodes Incorporated BC857BT-7-F

Overview

BC857BT-7-F from Diodes Incorporated is a PNP small-signal transistor in SOT523 package, rated for -45 V V_CEO, -100 mA I_C, and 150 mW power dissipation, with h_FE = 220–520 (at I_C = -2 mA, V_CE = -5 V), used in low-power switching and amplification circuits in automotive control modules and sensor interface stages.

For engineers reviewing the BC857BT-7-F datasheet, BC857BT-7-F pinout, BC857BT-7-F application, or BC857BT-7-F equivalent, key selection criteria include verified AEC-Q101 qualification, ultra-small SOT523 footprint, guaranteed h_FE binning (B grade), ESD robustness (4 kV HBM), and complementary pairing with BC847BT-7-F for differential or push-pull designs.

Technical Context

This PNP bipolar junction transistor uses epitaxial planar die construction to ensure stable gain and leakage performance across -55°C to +150°C operating range. Its V_CEO = -45 V and V_CBO = -50 V support reliable operation in 24 V automotive supply rails with margin.

The device delivers V_CE(SAT) ≤ -650 mV at I_C = -100 mA / I_B = -5 mA and f_T = 100 MHz at I_C = -10 mA, enabling use in medium-speed switching (e.g., LED drivers, logic-level translation) and low-noise preamplifier stages (NF = 10 dB at 1 MHz).

Key Specifications

Pinout & Package

SOT523 is an ultra-small surface-mount plastic package (1.60 × 1.60 × 0.75 mm) with gull-wing leads, optimized for high-density PCB layouts and automated placement. It features matte tin-plated terminals, UL 94V-0 flammability rating, and moisture sensitivity level 1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP small-signal transistor applications.

Compared with BC857BW-7-F, the BC857BT-7-F saves 40% board area and supports denser routing; versus MMBT3906LT1G, it adds AEC-Q101 assurance, tighter h_FE, and 5 V higher breakdown-critical for 24 V system robustness.

Availability

BC857BT-7-F is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor interfaces, and compact wearable power management requiring stable component supply and long-term lifecycle continuity.

Supply support for BC857BT-7-F 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, specializing in high-reliability components for automotive, industrial, and computing markets.

The BC857x series belongs to Diodes' AEC-Q101-qualified small-signal transistor portfolio, engineered specifically for space-constrained, thermally demanding automotive subsystems and precision analog front-ends.

FAQ

What is the marking code for BC857BT-7-F on the device body?

The top-marking for BC857BT-7-F is "3W", where "3" identifies the BC857 family and "W" denotes the B-grade h_FE bin. This matches Diodes' official marking specification in DS30275 Rev. 10–2, page 1.

Does BC857BT-7-F support lead-free reflow soldering per JEDEC J-STD-020?

Yes - BC857BT-7-F has matte tin-plated leads and is qualified for lead-free reflow up to 260°C peak temperature. Its moisture sensitivity level is 1, eliminating bake requirements prior to assembly.

How does the SOT523 package affect thermal performance compared to SOT23?

SOT523's smaller size reduces thermal mass and increases R_θJA to 833°C/W (vs. ~300°C/W for SOT23), limiting continuous power to 150 mW. Derating is required above 25°C ambient; full power is only usable below 50°C with minimal copper area.

Can BC857BT-7-F be used as a direct replacement for BC857B in legacy SOT23 designs?

No - BC857BT-7-F uses SOT523, which is not pin-compatible with SOT23. Pad layout, stencil aperture, and pick-and-place programming must be revised. Electrical specs are identical, but mechanical integration requires redesign.