NXP Semiconductors PMSTA55,115

Overview

PMSTA55 from NXP Semiconductors is a PNP general-purpose transistor in SOT323 (SC-70) package, rated for −60 V collector-emitter voltage, −500 mA continuous collector current, and 200 mW power dissipation at 25 °C ambient. It delivers DC current gain (h_FE) ≥100 at −10 mA and −100 mA collector currents, with −250 mV saturation voltage at −100 mA/−10 mA drive-used in telephony line interface stages and signal switching.

For engineers reviewing the PMSTA55 datasheet, PMSTA55 pinout, PMSTA55 application, or PMSTA55 equivalent, this page provides verified electrical parameters, validated SOT323 terminal mapping, confirmed telephony use cases, and two functionally comparable PNP transistors with documented voltage/current trade-offs.

Technical Context

The PMSTA55 operates as a silicon PNP bipolar junction transistor optimized for low-voltage, medium-current switching and amplification. Its −60 V V_CEO, −4 V V_EBO, and 50 MHz f_T support stable operation in analog signal paths and digital logic interfaces up to 100 MHz.

Thermal resistance of 625 K/W (junction-to-ambient, free air) and 150 °C maximum junction temperature define its derating envelope on FR4 PCBs. Cut-off leakage is specified at −100 nA (I_CBO) and −500 nA (I_EBO), confirming suitability for low-power standby circuits.

Key Specifications

Pinout & Package

SOT323 (SC-70) plastic surface-mounted package with 3 leads; dimensions: 2.2 mm × 1.35 mm × 0.95 mm (L × W × H), standard footprint for high-density PCB layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MMBTA55 and PN2907A, the PMSTA55 offers superior thermal efficiency per unit area due to its SOT323 footprint and guaranteed h_FE ≥100 at −100 mA-making it optimal for miniaturized, high-density telephony modules requiring stable gain across operating current.

Availability

PMSTA55 is available at Aetrix Electronics and suitable for telephony line interface, professional audio signal switching, and industrial sensor interface applications requiring stable component supply and long-term obsolescence management.

Supply support for PMSTA55 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

NXP Semiconductors is a global semiconductor company headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and communication markets.

The PMSTA55 belongs to NXP's general-purpose bipolar transistor product line, designed specifically for cost-sensitive, high-reliability analog and switching functions in professional telecommunication infrastructure.

FAQ

What is the maximum collector-emitter voltage rating for PMSTA55?

The PMSTA55 has a maximum collector-emitter voltage (V_CEO) rating of −60 V under open-base conditions. This rating is confirmed in Table 5 of the NXP datasheet revision 05 (2010) and defines the absolute limit for safe operation in PNP configurations. Exceeding −60 V risks permanent device breakdown. The PMSTA55 datasheet specifies no derating curve, so design margins must be applied externally based on system-level transient analysis.

Is PMSTA55 pin-compatible with PMSTA56?

No, PMSTA55 and PMSTA56 share identical SOT323 pinout (base-emitter-collector on pins 1–2–3) and mechanical footprint, but they are not functionally interchangeable without circuit review. The PMSTA56 is rated for −80 V V_CEO versus −60 V for PMSTA55, and both exhibit identical h_FE and V_CEsat specs. Substituting PMSTA56 for PMSTA55 may be acceptable in higher-voltage designs, but using PMSTA55 in place of PMSTA56 risks overvoltage failure.

What is the DC current gain (h_FE) specification for PMSTA55 at high current?

The PMSTA55 guarantees h_FE ≥100 at both I_C = −10 mA and I_C = −100 mA, with V_CE = −1 V (Table 7). This dual-point specification ensures predictable base drive requirements across its operational range. No typ/min/max spread is given for the −100 mA condition-only a minimum of 100 is assured. The PMSTA55 datasheet does not provide h_FE data above −100 mA.

Does PMSTA55 have a complementary NPN transistor?

Yes, the NXP-designated NPN complement to PMSTA55 is PMSTA05, as stated in Table 1 of the datasheet. Both share identical SOT323 packaging and matched voltage/current ratings (PMSTA05: 60 V V_CEO, 500 mA I_C). This pairing enables balanced push-pull or differential amplifier designs where matched gain and thermal characteristics are critical-such as in telephony hybrid circuits referenced in the PMSTA55 application notes.

What is the thermal resistance (R_th(j-a)) of PMSTA55 in free air?

The PMSTA55 has a junction-to-ambient thermal resistance (R_th(j-a)) of 625 K/W when mounted on an FR4 PCB with single-sided copper, tin-plated, and standard SOT323 footprint (Table 6). This value applies only in free-air convection conditions-not with heatsinking or forced airflow. At 25 °C ambient, this limits continuous power dissipation to 200 mW; exceeding that requires derating per the datasheet's thermal curves.