onsemi BC858C

Overview

BC858C from Fairchild Semiconductor is a PNP epitaxial silicon transistor in SOT-23 package, rated for V_CEO = −30 V, I_C = −100 mA, and P_C = 310 mW, with h_FE = 420–800 at I_C = −2 mA, used in low-noise amplifier and switching stages of portable audio and power management circuits.

For engineers reviewing the BC858C datasheet, pinout, applications, or equivalent options, key selection considerations include its guaranteed h_FE classification (C-grade), V_CE(sat) ≤ −300 mV at I_C = −10 mA / I_B = −0.5 mA, noise figure of 2 dB at 1 kHz, SOT-23 footprint compatibility, and complementary pairing with BC848C.

Technical Context

This PNP bipolar junction transistor operates in active, saturation, and cutoff regions with defined DC gain linearity across I_C = −0.1 to −100 mA. Its f_T = 150 MHz enables RF amplification up to mid-VHF band, while Cob = 6 pF at V_CB = −10 V supports stable high-frequency biasing.

The device features low V_BE(sat) (−700 mV typ. at I_C = −10 mA) and tight h_FE binning (420–800), enabling predictable current mirror accuracy and consistent switching thresholds in discrete logic and analog feedback paths.

Key Specifications

Pinout & Package

SOT-23 plastic surface-mount package with gull-wing leads; 1.30 mm × 2.90 mm footprint, 1.14 mm height, 0.95 mm lead pitch, and JEDEC-standard thermal pad layout.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC848C and MMBT3906, BC858C delivers superior gain consistency (C-bin), lower noise (2 dB vs. ≥4 dB), and lower V_CE(sat), making it preferred for precision analog and low-power audio applications where performance margins matter.

Availability

BC858C is available at Aetrix Electronics and suitable for portable audio systems, battery-powered sensor interfaces, and discrete power management circuits requiring stable component supply and long-term obsolescence resilience.

Supply support for BC858C 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

Fairchild Semiconductor was a U.S.-based semiconductor company specializing in power management, analog, and discrete components before its acquisition by ON Semiconductor in 2016.

The BC856–BC860 family was designed for high-reliability, low-noise, and high-gain discrete PNP/NPN amplification and switching in space-constrained consumer and industrial electronics.

FAQ

What is the guaranteed h_FE range for BC858C?

The BC858C has a guaranteed DC current gain (h_FE) range of 420 to 800 when measured at V_CE = −5 V and I_C = −2 mA. This C-grade binning ensures consistent amplification performance across production lots and eliminates need for post-manufacture gain sorting in BC858C-based designs.

Is BC858C suitable for low-noise audio preamplifier applications?

Yes, BC858C is suitable for low-noise audio preamplifier applications due to its specified noise figure of 2 dB at 1 kHz, V_CE = −5 V, I_C = −200 µA, and tight h_FE tolerance. These characteristics enable clean signal amplification in electret microphone biasing and sensor front-end stages without introducing measurable hiss.

What is the maximum power dissipation of BC858C and how is it derated?

The BC858C has a maximum collector power dissipation (P_C) of 310 mW at T_A = 25°C. Derating follows a linear slope of −2.48 mW/°C above 25°C ambient, reaching zero dissipation at approximately 150°C junction temperature. PCB copper area and airflow directly impact achievable power handling in real-world layouts.

Does BC858C have a documented SOT-23 pinout, and what is the terminal assignment?

Yes, BC858C uses the standard SOT-23 package with confirmed pinout: Pin 1 = Base, Pin 2 = Emitter, Pin 3 = Collector. This assignment is explicitly stated in the Fairchild BC856–BC860 datasheet Rev. A2 and verified across distributor footprints (Digi-Key, Mouser) and IPC-7351B land pattern references.

How does BC858C compare to BC857C in terms of voltage ratings?

BC858C has V_CEO = −30 V and V_CBO = −30 V, whereas BC857C has V_CEO = −45 V and V_CBO = −50 V. The BC858C is optimized for lower-voltage rails (e.g., 3.3 V or 5 V systems), offering tighter gain binning and lower saturation voltage at the expense of reduced breakdown margin compared to BC857C.