Nexperia USA Inc. BC858B,235

Overview

BC858B,235 from Nexperia is a PNP general-purpose bipolar junction transistor in SOT23 (TO-236AB) package, rated for −30 V V_CEO, −100 mA I_C, and 220–475 h_FE at V_CE = −5 V, I_C = −2 mA. It serves as a low-voltage, low-current switching or amplification device in signal conditioning, level shifting, and discrete logic interface circuits.

For engineers reviewing the BC858B,235 datasheet, BC858B,235 pinout, BC858B,235 application, or BC858B,235 equivalent, key selection criteria include its PNP polarity, SOT23 footprint compatibility, guaranteed DC current gain range, −30 V collector-emitter breakdown rating, and thermal resistance of 500 K/W on FR4 PCB.

Technical Context

This transistor operates in active, saturation, and cutoff regions with defined V_BE(sat) ≤ −850 mV at I_C = −100 mA/I_B = −5 mA and V_CE(sat) ≤ −650 mV under same conditions. Its f_T is 100 MHz at V_CE = −5 V, I_C = −10 mA, enabling use in low-frequency analog and digital switching up to several tens of MHz.

The device features low leakage: I_CBO ≤ −4 µA at T_j = 150 °C and I_EBO ≤ −100 nA, with thermal resistance R_th(j-a) = 500 K/W on standard FR4 PCB - critical for thermal design in space-constrained consumer and industrial PCBs.

Key Specifications

Pinout & Package

SOT23 (TO-236AB) plastic surface-mounted package with 3 leads; compact 2.9 mm × 1.3 mm footprint, 1.1 mm height, and standard reflow-compatible pad layout per Figure 15.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP general-purpose transistor applications.

Compared with BC858B, BC857B offers higher voltage tolerance while maintaining identical gain and package, making it a drop-in upgrade for 12 V systems; MMBT3906 trades guaranteed gain consistency for broader distributor availability but demands revised base bias design.

Availability

BC858B,235 is available at Aetrix Electronics and suitable for LED driver circuits, microcontroller GPIO interfacing, discrete logic inverters, and power supply enable switches requiring stable component supply and SOT23 footprint compatibility.

Supply support for BC858B,235 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 high-volume, high-reliability essential semiconductors for automotive, industrial, mobile, and computing markets.

The BC856/BC857/BC858 series targets cost-sensitive, space-constrained applications requiring robust, standardized PNP transistors with guaranteed gain bins and AEC-Q200-aligned manufacturing processes.

FAQ

What is the maximum allowable collector-emitter voltage for BC858B,235?

The absolute maximum collector-emitter voltage (V_CEO) for BC858B,235 is −30 V with the base open, as specified in Table 6 of the Nexperia datasheet Rev. 9. Exceeding this value risks permanent junction breakdown, especially under transient conditions or elevated temperature.

Does BC858B,235 have a guaranteed DC current gain range?

Yes - BC858B,235 is binned to h_FE = 220–475 at V_CE = −5 V and I_C = −2 mA, per Table 2 and Table 8. This guaranteed range ensures consistent base drive requirements across production lots without design iteration.

Can BC858B,235 be used in place of BC857B in existing designs?

No - BC858B has V_CEO = −30 V versus BC857B's −45 V, and its h_FE curve shifts slightly at higher currents (Fig. 6 vs. Fig. 2). Substitution requires verification of voltage margin and gain-dependent timing in saturation, particularly in 12 V systems.

What is the thermal resistance of BC858B,235 on a standard PCB?

R_th(j-a) is 500 K/W when mounted on a single-sided FR4 PCB with 35 µm copper, tin-plated traces, and standard SOT23 footprint (Table 7). This value assumes no thermal vias or copper pour; adding 2–4 thermal vias beneath the pad can reduce it by 20–30%.