Nexperia USA Inc. BC858W-QX

Overview

BC858W-Q from Nexperia is a PNP general-purpose transistor in SOT323 (SC-70) package, rated for −30 V V_CEO, −100 mA I_C, and DC current gain (h_FE) of 125–800 at V_CE = −5 V and I_C = −2 mA. It serves as a low-power switching or linear amplification device in automotive signal conditioning, sensor interface, and power management circuits.

For engineers reviewing the BC858W-Q datasheet, BC858W-Q pinout, BC858W-Q application, or BC858W-Q equivalent, key selection criteria include its AEC-Q101 qualification, −30 V breakdown rating, SOT323 thermal resistance (625 K/W), and h_FE binning consistency across temperature (−55 °C to +150 °C).

Technical Context

This PNP bipolar junction transistor operates with base-emitter forward bias and collector-emitter reverse bias in standard active or saturation modes. Its design supports low-current analog amplification (I_C ≤ −100 mA) and digital switching (V_CE(sat) ≤ −600 mV at I_C = −100 mA, I_B = −5 mA), with guaranteed performance over −55 °C to +150 °C ambient range.

The device features low leakage (I_CBO ≤ −4 µA at T_j = 150 °C), tight h_FE distribution (125–800), and stable V_BE(sat) (≤ −850 mV), enabling predictable biasing in discrete amplifier stages and load-switch configurations without external compensation.

Key Specifications

Pinout & Package

SOT323 (SC-70) plastic surface-mounted package: 1.3 mm × 1.8 mm footprint, 0.95 mm height, 3-lead configuration with gull-wing terminations optimized for reflow soldering per IPC-7095.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BC857W-Q, BC858W-Q offers tighter voltage margin for cost-sensitive 12 V automotive modules; versus BC848W-Q, it enables high-side sourcing without level-shifting, preserving signal integrity in grounded-load configurations.

Availability

BC858W-Q is available at Aetrix Electronics and suitable for automotive body electronics, industrial sensor interfaces, and portable medical diagnostics requiring stable component supply with AEC-Q101 compliance and long-term lifecycle assurance.

Supply support for BC858W-Q 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 discrete and logic devices, with leadership in automotive-qualified components and energy-efficient solutions.

The BC858W-Q belongs to Nexperia's AEC-Q101-qualified general-purpose transistor family, engineered for robustness in automotive signal routing, power switching, and sensor interfacing where space, thermal, and reliability constraints dominate.

FAQ

Is BC858W-Q suitable for high-frequency switching above 10 MHz?

No. With f_T = 100 MHz only at I_C = −10 mA, BC858W-Q is optimized for DC to ~1 MHz applications. Its transition frequency drops significantly below 10 mA, and parasitic capacitances (C_c = 3 pF, C_e = 12 pF) limit slew rate in fast-switching circuits. Use RF-optimized transistors for >10 MHz operation.

What is the maximum allowable PCB copper area for thermal relief at 100 mA continuous current?

At I_C = −100 mA and V_CE(sat) = −600 mV, power dissipation is 60 mW. With R_th(j-a) = 625 K/W, junction rise is ~37.5 °C above ambient. No additional copper is required beyond the standard SOT323 footprint (2.65 × 2.35 mm solder lands), but doubling pad area reduces R_th(j-a) by ~15% per IPC-7095 guidelines.

Does BC858W-Q require base resistors in all switching applications?

Yes. The base-emitter junction behaves as a diode with V_BE ≈ −750 mV. Without a series resistor, excessive I_B can exceed I_BM = −200 mA, causing permanent damage. For I_C = −100 mA and h_FE = 125, minimum R_B = (V_IN − 0.75 V)/0.8 mA ensures safe saturation while avoiding overdrive.

How does BC858W-Q perform under transient thermal stress during pulsed operation?

Per Figure 1, Z_th(j-a) drops from 625 K/W (DC) to ~120 K/W at 10 ms pulse width (duty cycle 0.02). At I_C = −200 mA peak (I_CM), 10 ms pulses generate ~240 mW peak power, resulting in <30 °C junction rise-well within the 150 °C T_j limit. Thermal response is fully characterized in the datasheet for design validation.