onsemi BCX17LT1

Overview

BCX17LT1 from ON Semiconductor (formerly Motorola) is a PNP silicon small-signal transistor in SOT-23 package, rated for 45 V_CEO, 500 mA continuous collector current, and 225 mW power dissipation on FR-5 board. It delivers h_FE = 100–600 at I_C = 100 mA, V_CE = 1.0 V, and is used in low-power switching and linear amplification circuits such as LED drivers and sensor interface stages.

For engineers reviewing the BCX17LT1 datasheet, pinout, applications, or equivalent options, key selection criteria include its PNP polarity, V_CEO = 45 V rating, h_FE range across operating currents, thermal performance on standard PCBs, and compatibility with SOT-23 reflow profiles.

Technical Context

The BCX17LT1 operates as a general-purpose PNP bipolar junction transistor with base-emitter and base-collector junctions optimized for low-to-medium current switching and analog amplification. Its V_BRCEO = 45 V and V_BRCES = 50 V support robust off-state blocking in 24 V rail systems.

Thermal design relies on R_θJA = 556 °C/W (FR-5) or 417 °C/W (alumina), enabling operation up to T_J = 150 °C. Saturation voltage V_CE(sat) ≤ 0.62 V at I_C = 500 mA / I_B = 50 mA confirms suitability for efficient low-side switch configurations.

Key Specifications

Pinout & Package

SOT-23 (TO-236AB) plastic surface-mount package, 3-pin, case style 318–08, footprint compliant with JEDEC MO-178. Dimensions: 2.80 × 1.20 × 0.95 mm (L × W × H).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BCX17LT1, MMBT3906 offers broader distribution but reduced voltage headroom, while BC807-16 provides higher power capability at the cost of gain flexibility-both require validation of base drive and thermal performance in the target layout.

Availability

BCX17LT1 is available at Aetrix Electronics and suitable for industrial sensor interfaces, automotive body control modules, LED driver circuits, and power supply enable switches requiring stable component supply and long-term manufacturability.

Supply support for BCX17LT1 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

ON Semiconductor is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, communications, computing, and consumer markets.

The BCX17LT1 belongs to Motorola's legacy small-signal transistor family, designed for general-purpose amplification and switching in space-constrained, cost-sensitive applications where reliability and standardized SOT-23 packaging are essential.

FAQ

What is the maximum collector-emitter voltage rating for BCX17LT1?

The BCX17LT1 has a maximum collector-emitter voltage rating (V_CEO) of 45 Vdc at I_C = 10 mA and I_B = 0. This rating applies under open-base conditions and defines the upper limit for safe operation in common-emitter configurations. Exceeding this voltage risks avalanche breakdown and permanent device damage. The BCX17LT1 also supports V_BRCES = 50 Vdc with emitter open, useful for load-dump transient tolerance in automotive applications.

Is BCX17LT1 a PNP or NPN transistor?

The BCX17LT1 is a PNP bipolar junction transistor. Its pinout is Base (pin 1), Emitter (pin 2), Collector (pin 3) in SOT-23 package. As a PNP device, it conducts when the base is driven ~0.7 V below the emitter, making it suitable for high-side switching and complementary circuit topologies. This polarity is confirmed by negative voltage/current conventions in the original Motorola datasheet and consistent with its device marking "T1" in the BCX series family.

What is the DC current gain (h_FE) range for BCX17LT1 at typical operating conditions?

The BCX17LT1 exhibits h_FE = 100–600 at I_C = 100 mA and V_CE = 1.0 Vdc, per the Motorola datasheet. At higher currents (I_C = 300 mA), h_FE drops to 70–? (min not specified), and at I_C = 500 mA, it falls further to 40–? (min not specified). Designers should use the 100–600 range for base resistor calculations in linear amplifier stages and verify saturation with I_B ≥ I_C/10 for switching applications.

Can BCX17LT1 be used in surface-mount reflow processes?

Yes, BCX17LT1 is qualified for standard SMT reflow soldering. Its SOT-23 package complies with JEDEC MO-178 and supports peak temperatures up to 260 °C for ≤ 10 seconds. Preheating is recommended to limit thermal gradient; the datasheet specifies delta-T ≤ 100 °C between preheat and soldering zones and max gradient ≤ 5 °C/s during cooling. These constraints ensure mechanical integrity and prevent delamination or bond wire failure in the BCX17LT1 die assembly.

What is the thermal resistance (R_θJA) of BCX17LT1 on a standard FR-5 PCB?

The BCX17LT1 has a junction-to-ambient thermal resistance (R_θJA) of 556 °C/W when mounted on a 1.0 × 0.75 × 0.062 inch FR-5 board at T_A = 25 °C. This value assumes use of the minimum recommended SOT-23 footprint. Under these conditions, the device dissipates 225 mW at its maximum rated junction temperature of 150 °C. For higher power operation, alumina substrates reduce R_θJA to 417 °C/W, enabling 300 mW dissipation.