Diodes Incorporated BC857BT-7

Overview

BC857BT-7 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, used in low-power switching and amplification circuits in portable electronics and sensor interfaces.

For engineers reviewing the BC857BT-7 datasheet, BC857BT-7 pinout, BC857BT-7 application, or BC857BT-7 equivalent, key selection criteria include verified V_CEO derating above 85°C, confirmed SOT523 thermal resistance (R_θJA = 833 °C/W), h_FE binning consistency across temperature, and AEC-Q101 qualification for automotive-grade reliability.

Technical Context

This PNP bipolar junction transistor uses epitaxial planar die construction to ensure stable gain and low leakage across -55°C to +150°C operating range. Its ultra-small SOT523 footprint supports high-density PCB layouts while maintaining JEDEC-compliant ESD robustness (HBM 4 kV, MM 400 V).

It operates with V_BE(ON) = -600 to -820 mV at I_C = -2 to -10 mA and delivers f_T = 100 MHz at V_CE = -5 V, I_C = -10 mA - enabling use in audio preamplifiers and digital logic level translation where low saturation voltage and predictable current gain are required.

Key Specifications

Pinout & Package

SOT523 is a 3-pin ultra-small surface-mount plastic package with dimensions 1.60 × 1.60 × 0.55 mm (L × W × H), featuring matte tin-plated leads, 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 and MMBT857LT1G, BC857BT-7 uniquely combines AEC-Q101 qualification, SOT523 miniaturization, and extended h_FE range - making it optimal for space-constrained automotive and industrial edge devices requiring guaranteed reliability and gain stability.

Availability

BC857BT-7 is available at Aetrix Electronics and suitable for automotive body control units, portable sensor interfaces, and industrial PLC input conditioning requiring stable component supply and long-term lifecycle support.

Supply support for BC857BT-7 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 BC857 series belongs to Diodes' AEC-Q101-qualified small-signal transistor portfolio, designed specifically for robust, miniaturized switching and amplification in harsh-environment electronic control units.

FAQ

What is the maximum operating temperature for BC857BT-7?

The BC857BT-7 has an operating junction temperature range of -55°C to +150°C and storage temperature range matching that. At ambient temperatures above 85°C, power dissipation must be linearly derated per Fig. 1 in DS30275 - e.g., to ~90 mW at 85°C and ~30 mW at 125°C - based on its 833 °C/W thermal resistance.

Is BC857BT-7 pin-compatible with BC847BT-7?

No - BC857BT-7 is a PNP transistor while BC847BT-7 is its complementary NPN counterpart; both share identical SOT523 pinout (E-B-C), but polarity reversal means direct substitution would invert circuit behavior. They are electrically complementary, not functionally interchangeable, and require redesign of biasing and signal paths.

Does BC857BT-7 require external base resistors in switching applications?

Yes - because it is a current-controlled device, a series base resistor is mandatory to limit I_B and prevent damage. For example, driving a 10 mA collector load with h_FE = 220 requires ≥100 µA I_B; with V_BE ≈ -0.7 V and 3.3 V GPIO, a 26 kΩ resistor ensures safe operation while allowing full saturation.

How does the SOT523 package affect soldering process design?

The SOT523's 0.55 mm height and 0.22 mm lead width demand precise stencil aperture design (typically 0.25 × 0.4 mm) and reflow profile tuning - peak temperature 245°C ±5°C, ramp rate ≤3°C/s, and soak time 60–90 s at 150–200°C - to avoid tombstoning or insufficient wetting, especially given its moisture sensitivity level 1 rating.