onsemi BCW33LT3G

Overview

BCW33LT3G from onsemi is an NPN silicon general-purpose transistor in SOT-23 package, rated for 32 V_CEO, 100 mA continuous collector current, and DC current gain (h_FE) of 420–800 at 2 mA/5 V. It delivers low V_CE(sat) ≤ 0.25 V at I_C/I_B = 20, supports operation from −55 °C to +150 °C, and is used in signal amplification and switching circuits in portable audio and sensor interface modules.

For engineers reviewing the BCW33LT3G datasheet, pinout, applications, or equivalent options, key selection considerations include its Pb-free SOT-23 footprint, verified noise figure ≤10 dB at 1 kHz, thermal resistance of 417 °C/W on alumina substrate, and validated performance under pulsed duty cycles up to 2% with t_on/t_off < 300 ns.

Technical Context

This NPN bipolar junction transistor operates in linear and saturated switching modes, with base-emitter turn-on voltage specified between 0.55 V and 0.70 V at I_C = 2 mA. Its output capacitance (C_obo) is ≤4.0 pF at V_CB = 10 V, enabling stable high-frequency small-signal amplification up to f_T ≈ 250 MHz (typical, per family characterization).

Thermal design is supported by dual dissipation ratings: 225 mW on FR-5 board (derated 1.8 mW/°C above 25 °C) and 300 mW on alumina substrate (derated 2.4 mW/°C), corresponding to R_JA values of 556 °C/W and 417 °C/W respectively - critical for compact PCB layouts with limited airflow.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) plastic surface-mount package, 3-pin, Pb-free, marked "D3M" (date code + Pb-free indicator). Dimensions per Case 318-08: D = 2.80–3.04 mm, E = 1.20–1.40 mm, e = 1.78–2.04 mm, L = 0.10–0.30 mm.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BCW33LT3G, BC847BT-7-F offers higher voltage tolerance but reduced current gain, while MMBT3904LT1G provides broader industry adoption and tighter parametric screening at the expense of analog performance - making BCW33LT3G optimal for noise-sensitive, medium-gain linear applications.

Availability

BCW33LT3G is available at Aetrix Electronics and suitable for portable audio preamps, industrial sensor interfaces, LED indicator drivers, and microcontroller GPIO expander circuits requiring stable component supply and RoHS-compliant sourcing.

Supply support for BCW33LT3G 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and IoT markets.

The BCW33LT3G belongs to onsemi's general-purpose bipolar transistor product line, designed for reliable, low-cost signal amplification and switching in space-constrained consumer and industrial electronics.

FAQ

What is the maximum operating temperature for BCW33LT3G?

The BCW33LT3G has a specified junction and storage temperature range of −55 °C to +150 °C. This allows deployment in harsh environments such as automotive engine compartments or industrial motor control enclosures. Derating of power dissipation begins above 25 °C per the thermal characteristics table, and sustained operation near 150 °C requires careful thermal design using the 417 °C/W R_JA value on alumina substrate. The BCW33LT3G must not exceed this absolute maximum to avoid permanent degradation.

Does BCW33LT3G support Pb-free reflow soldering?

Yes, BCW33LT3G is explicitly designated as Pb-free (marked with "G" suffix and "M" date code), compliant with J-STD-020 moisture sensitivity level 1 and RoHS Directive 2011/65/EU. It supports standard lead-free reflow profiles with peak temperatures up to 260 °C. The device's SOT-23 package is qualified for IPC-A-610 Class 2 and Class 3 assembly, and its thermal response data (Figure 16) enables accurate transient junction temperature modeling during reflow.

What is the typical noise figure of BCW33LT3G and at what conditions is it measured?

The BCW33LT3G has a maximum noise figure (NF) of 10 dB, measured at V_CE = 5.0 Vdc, I_C = 0.2 mAdc, R_S = 2.0 kΩ, f = 1.0 kHz, and bandwidth = 200 Hz. This value is confirmed in the Electrical Characteristics table and supported by Figure 7 (Noise Figure Contours). The BCW33LT3G's low-noise capability makes it suitable for microphone preamplifiers and precision analog sensor conditioning where signal integrity below 10 kHz is critical.

Can BCW33LT3G be used in switching applications with fast transitions?

Yes, BCW33LT3G is characterized for switching performance: typical turn-on time (t_on) and turn-off time (t_off) are both under 300 ns at V_CC = 3.0 V, I_C/I_B = 10, and T_J = 25 °C (Figures 12 and 13). These values confirm suitability for PWM-driven LED dimming, digital logic interfacing, and low-duty-cycle pulse generation up to ~1 MHz. The BCW33LT3G's C_obo ≤ 4.0 pF further supports clean edge fidelity in high-speed switching.

How does the DC current gain (h_FE) of BCW33LT3G vary with collector current?

The BCW33LT3G specifies h_FE = 420–800 at I_C = 2.0 mAdc and V_CE = 5.0 Vdc. Per Figure 9 (Collector Characteristics) and Figure 11 (Temperature Coefficients), h_FE peaks near 1–10 mA and decreases at both lower (<0.1 mA) and higher (>50 mA) currents. At I_C = 100 mA, h_FE drops to ~100–200 (inferred from family curves). Designers should verify gain at the intended operating point using the BCW33LT3G's published static curves rather than relying solely on the 2 mA test condition.