Diodes Incorporated BC857A-7-F

Overview

BC857A-7-F from Diodes Incorporated is a PNP small-signal transistor in SOT23 package, rated for V_CEO = −45 V, I_C = −100 mA, and h_FE = 125–250 at I_C = −2 mA. It delivers V_CE(sat) ≤ −300 mV at I_C = −10 mA / I_B = −0.5 mA and operates across −55°C to +150°C. It is used in low-power switching and audio-frequency amplification stages in industrial control interfaces.

For engineers reviewing the BC857A-7-F datasheet, BC857A-7-F pinout, BC857A-7-F application, or BC857A-7-F equivalent, key selection criteria include guaranteed h_FE binning (A-grade), JEDEC-qualified reliability, SOT23 thermal performance (R_θJA = 403°C/W), and RoHS/"Green" compliance with <900 ppm Br+Cl.

Technical Context

This PNP bipolar junction transistor uses epitaxial base construction for stable DC current gain and low saturation voltage. Its h_FE range (125–250) and f_T ≥ 100 MHz support linear amplification up to mid-audio frequencies and fast switching in discrete logic-level translators.

The device is characterized under pulsed conditions (≤300 µs, ≤2% duty cycle) for V_CE(sat), V_BE(on), and h_FE. Thermal derating follows a linear 3.5 mW/°C reduction above +25°C ambient when mounted on minimum pad layout.

Key Specifications

Pinout & Package

Package: SOT23 - Surface-mount plastic package with 3 terminals, 0.008 g mass, UL 94V-0 rated molding compound, and matte tin-plated leads.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC857B-7-F and MMBT3906LT1G, BC857A-7-F provides the most conservative h_FE range for predictable base drive design and the highest V_CEO among common SOT23 PNP transistors, making it optimal for 24 V industrial interfaces requiring margin.

Availability

BC857A-7-F is available at Aetrix Electronics and suitable for industrial sensor interfaces, low-voltage logic level shifting, and LED status indication requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for BC857A-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 industrial, automotive, and computing markets.

BC857A-7-F belongs to the BC856A–BC858C PNP transistor family, designed specifically for cost-sensitive, high-volume switching and AF amplification applications demanding JEDEC qualification and green compliance.

FAQ

What is the maximum operating temperature for BC857A-7-F?

The BC857A-7-F is rated for junction and storage temperatures from −55°C to +150°C. Its thermal resistance (R_θJA = 403°C/W) means that at 310 mW power dissipation and +25°C ambient, junction temperature reaches approximately +155°C-exceeding the absolute maximum. Derating to ≤220 mW is required for reliable operation at +85°C ambient.

Is BC857A-7-F suitable for automotive applications?

BC857A-7-F itself is not AEC-Q200 qualified; Diodes offers automotive-compliant variants under separate part numbers (e.g., BC857AQ). The standard BC857A-7-F meets JEDEC reliability standards and is widely used in industrial controls, but automotive designs require the Q-suffix versions with full PPAP documentation and extended test coverage.

How does the "A" suffix affect h_FE specification?

The "A" suffix denotes the lowest h_FE bin in the BC857 series: 125–250 at I_C = −2 mA, V_CE = −5 V. This provides the most conservative gain guarantee for base-drive calculations, reducing risk of insufficient turn-on in margin-constrained circuits compared to "B" (220–475) or "C" (420–800) grades.

Can BC857A-7-F replace BC858A-7-F in existing designs?

No-BC858A-7-F has V_CEO = −30 V and V_CBO = −30 V, while BC857A-7-F is rated for −45 V and −50 V respectively. Substituting BC857A-7-F may be acceptable if voltage stress remains below −30 V, but the reverse substitution risks breakdown. Always verify worst-case V_CE in the target circuit before interchange.