onsemi BCW70LT1

Overview

BCW70LT1 from onsemi is a PNP silicon general-purpose transistor in SOT-23 package, rated for −45 V_CEO, −100 mA continuous collector current, and DC current gain (h_FE) of 215–500 at −2 mA/−5 V. It delivers low V_CE(sat) (≤ −0.3 V) and V_BE(on) (−0.6 to −0.75 V), supporting reliable switching and amplification in compact analog and digital interface circuits.

For engineers reviewing the BCW70LT1 datasheet, pinout, applications, or equivalent options, key selection considerations include its PNP polarity, SOT-23 footprint compatibility, thermal derating behavior on FR-5 vs. alumina substrates, noise performance at low collector currents, and Pb-free compliance per J-STD-609.

Technical Context

The BCW70LT1 operates as a discrete bipolar junction transistor with fixed PNP polarity, requiring external base current control for saturation or active-region biasing. Its h_FE range (215–500) supports predictable current amplification across production lots, while V_(BR)CEO = −45 V and V_(BR)EBO = −5.0 V define safe operating limits under reverse-biased conditions.

Thermal design relies on two distinct R_JA values: 556 °C/W on FR-5 board and 417 °C/W on alumina substrate - indicating layout-dependent power handling. Small-signal parameters include C_obo ≤ 7.0 pF and NF ≤ 10 dB at 1 kHz, confirming suitability for low-noise preamplifier stages and moderate-frequency switching up to ~100 MHz.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) package, 3-pin surface-mount, case 318, style 6. Dimensions: 2.90 mm × 1.30 mm × 1.00 mm (L × W × H), with 1.90 mm lead pitch. RoHS-compliant, Pb-free finish.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BCW70LT1, BC807-16LT1G offers higher current capacity but no guaranteed low-noise spec, while MMBT3906LT1G trades off saturation voltage and noise performance for wider distribution and lower unit cost - making BCW70LT1 optimal where balanced gain, low-loss switching, and verified noise behavior are jointly required.

Availability

BCW70LT1 is available at Aetrix Electronics and suitable for LED driver circuits, level-shifting interfaces, analog sensor signal conditioning, and power supply enable control requiring stable component supply across automotive infotainment, industrial PLC I/O modules, and medical diagnostic equipment.

Supply support for BCW70LT1 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, sensors, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BCW70LT1 belongs to onsemi's general-purpose bipolar transistor product line, designed for cost-effective, reliable switching and amplification in space-constrained PCB layouts where SOT-23 footprint and Pb-free compliance are mandatory.

FAQ

What is the maximum continuous collector current rating for the BCW70LT1?

The BCW70LT1 has a maximum continuous collector current (I_C) rating of −100 mAdc at T_A = 25°C. This value decreases linearly with ambient temperature above 25°C at 1.8 mW/°C on FR-5 board, meaning usable current drops to approximately −60 mA at 85°C ambient. Derating must be applied per the thermal characteristics table in the official BCW70LT1 datasheet to avoid junction overheating.

Is the BCW70LT1 pin-compatible with other SOT-23 PNP transistors like the MMBT3906?

Yes, the BCW70LT1 uses standard SOT-23 (TO-236AB) package with pin 1 = Base, pin 2 = Emitter, pin 3 = Collector - matching the MMBT3906LT1G pinout. However, electrical differences exist: BCW70LT1 offers lower V_CE(sat) (≤ −0.3 V vs. ≤ −0.4 V) and specified noise figure (≤ 10 dB), whereas MMBT3906LT1G emphasizes broader current capability (−200 mA) and tighter h_FE binning. Layout reuse is possible, but functional validation is required.

Does the BCW70LT1 meet RoHS and Pb-free requirements?

Yes, the BCW70LT1 is manufactured as a Pb-free device compliant with J-STD-609 Class 2a and RoHS Directive 2011/65/EU. The "M" marking on the package denotes Pb-free finish, and the device uses matte tin plating over copper leadframe. Full compliance documentation, including substance declarations and test reports, is available from onsemi upon request for BCW70LT1.

What is the typical noise figure of the BCW70LT1 and under what conditions is it measured?

The BCW70LT1 has a maximum noise figure (NF) of 10 dB, measured at I_C = −0.2 mAdc, V_CE = −5.0 Vdc, R_S = 2.0 kΩ, f = 1.0 kHz, and BW = 200 Hz. This specification is validated per the test setup shown in Figure 2 of the BCW70LT1 datasheet and reflects input-referred noise performance relevant to low-level analog signal amplification stages.

Can the BCW70LT1 be used in high-frequency switching applications above 10 MHz?

The BCW70LT1 exhibits a current-gain bandwidth product (f_T) of approximately 100 MHz at I_C = −10 mA (per Figure 12), supporting switching operation up to ~10–20 MHz with acceptable gain roll-off. However, its C_obo of ≤ 7.0 pF and documented turn-off time (t_f) of ~30 ns indicate diminishing performance beyond 50 MHz. For >50 MHz RF switching, dedicated RF transistors such as the MMBTH10 are recommended over BCW70LT1.