Nexperia USA Inc. PMST5550,115

Overview

PMST5550 from Nexperia is an NPN high-voltage transistor in SOT323 (SC-70) package, rated for 140 V V_CEO, 300 mA I_C, and 60 minimum h_FE at 1 mA. It operates up to 150 °C junction temperature and delivers 100 MHz f_T, serving as a switching and amplification device in telephony line interface circuits.

For engineers reviewing the PMST5550 datasheet, PMST5550 pinout, PMST5550 application, or PMST5550 equivalent, key selection criteria include its 160 V V_CBO rating, low 200 mW P_tot at T_amb ≤ 25 °C, SC-70 thermal resistance of 625 K/W, and verified performance in high-voltage analog switching with <250 mV V_CEsat at 50 mA/5 mA drive.

Technical Context

This discrete NPN bipolar junction transistor is optimized for high-voltage, low-current operation where robust breakdown margins and stable DC gain are required. Its 160 V V_CBO and 140 V V_CEO support reliable operation in off-hook telephone line circuits and isolated signal switching stages.

The device exhibits 6 pF C_c and 30 pF C_e capacitance at specified bias conditions, enabling predictable frequency response up to 100 MHz f_T. Its 8 dB noise figure at 200 µA and 2 kΩ source impedance confirms suitability for low-noise preamplifier roles in telephony front-ends.

Key Specifications

Pinout & Package

Package: SOT323 (SC-70), plastic surface-mounted, 3-lead, 1.3 mm pitch, 2.0 × 1.25 × 0.95 mm body size.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN high-voltage transistor applications.

Compared with BC847BW and MMBT5551, PMST5550 uniquely balances 140 V V_CEO, SOT323 compactness, and 625 K/W thermal resistance-making it optimal for space-constrained, high-voltage telephony modules where both voltage headroom and board area are critical.

Availability

PMST5550 is available at Aetrix Electronics and suitable for telephone line interface, off-hook detection, and high-voltage signal switching requiring stable component supply and long-term industrial availability.

Supply support for PMST5550 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 specializing in high-performance, high-reliability discrete, logic, and MOSFET devices, headquartered in Nijmegen, Netherlands.

The PMST5550 belongs to Nexperia's high-voltage bipolar transistor product line, engineered specifically for analog signal conditioning and switching in legacy and modern telecommunication infrastructure.

FAQ

Is PMST5550 automotive-qualified?

No. Per Nexperia's revision history, PMST5550 was explicitly changed to non-automotive qualification in v.5 (October 2024). It lacks AEC-Q101 testing and is not approved for safety-critical vehicle systems. Automotive alternatives must be selected from Nexperia's dedicated -Q qualified portfolio.

What is the maximum allowable continuous power dissipation at 70 °C ambient?

At 70 °C ambient, derated P_tot is 120 mW. This is calculated using the 200 mW rating at 25 °C and R_th(j-a) = 625 K/W: P_tot = (150 °C − 70 °C) / 625 K/W = 0.128 W ≈ 120 mW. Operation beyond this requires heatsinking or forced airflow.

Can PMST5550 replace BC546 in existing designs?

No. BC546 has 65 V V_CEO and TO-92 packaging, while PMST5550 offers 140 V V_CEO but in SOT323. Direct replacement risks voltage overstress failure in BC546-based 48 V systems and requires PCB footprint redesign due to different package dimensions and thermal behavior.

Does PMST5550 support pulsed operation beyond 300 µs?

No. The datasheet specifies h_FE and V_CEsat test conditions with pulse width ≤ 300 µs and duty cycle δ ≤ 0.02. Longer pulses increase junction temperature beyond safe limits due to 625 K/W R_th(j-a), risking thermal runaway unless externally cooled or significantly derated.