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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics STPSA42

Name: STPSA42
Brand: STMicroelectronics
SKU: STPSA42
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STPSA42

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA)

Datasheet:: STPSA42.pdf

Description:: TRANS NPN 300V 0.5A TO-92-3

Quantity:: RFQ Add To RFQ list

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Inventory:3,254

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Product details

Overview

STPSA42 from STMicroelectronics is a silicon epitaxial planar NPN high-voltage transistor in TO-92 package, rated for V_CBO = 300 V, V_CEO = 300 V, I_C = 0.5 A, and P_tot = 625 mW at T_C = 25 °C; used for RGB cathode current control in video amplifier circuits and hook-switch/dialer functions in telephone wireline interfaces.

For engineers reviewing the STPSA42 datasheet, STPSA42 pinout, STPSA42 application, or STPSA42 equivalent, key selection criteria include high-voltage breakdown capability (300 V), DC current gain (h_FE ≥ 25 @ I_C = 1 mA), saturation voltage (V_CE(sat) = 0.5 V @ I_C = 20 mA), thermal resistance (R_thj-amb = 200 °C/W), and complementary pairing with STPSA92.

Technical Context

This NPN bipolar junction transistor features a high-voltage planar structure optimized for linear and switching operation in analog signal paths requiring stable gain and low leakage. Its 300 V collector-base and collector-emitter breakdown ratings support operation in off-hook telephone line interface circuits and RGB driver stages where transient overvoltage immunity is critical.

The device delivers h_FE = 25–40 across I_C = 1–30 mA at V_CE = 10 V, with f_T = 50 MHz at I_C = 10 mA/V_CE = 20 V, enabling use in medium-frequency video amplification. Low capacitance values (C_CBO = 6 pF, C_EBO = 22 pF) support bandwidth preservation in cathode-current-controlled RGB stages.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CBO	300 V - Enables safe operation in telephone line interface circuits exposed to ringing voltages up to 170 V RMS with margin.
V_CEO	300 V - Supports direct connection to unregulated HV rails in RGB cathode drivers without external clamping.
I_C	0.5 A - Sufficient for driving cathode loads in CRT-based RGB video output stages and hook-switch current paths.
h_FE	25–40 - Provides predictable DC biasing stability in linear amplifier configurations with minimal base drive requirements.
f_T	50 MHz - Allows use in RGB video amplifiers operating up to ~10 MHz bandwidth with adequate gain margin.
R_thj-amb	200 °C/W - Requires heatsinking or derating above ~300 mW in still-air environments to maintain T_j ≤ 150 °C.
C_CBO	6 pF - Minimizes Miller effect in high-gain common-emitter video amplifier stages at 20 MHz test frequency.

Pinout & Package

TO-92 package: molded plastic case with three leads, through-hole mountable, standard lead spacing (P0 = 12.5–12.9 mm), and defined mechanical dimensions per STMicroelectronics mechanical drawing.

Pin/Terminal	Circuit Role	Design Meaning
Emitter (E)	Current sink terminal	Connected to ground or low-impedance return path; supports 0.5 A continuous conduction with V_EB ≤ 5 V.
Base (B)	Control input	Accepts 2 mA drive for full saturation; V_BE(sat) = 0.9 V ensures predictable turn-on threshold in digital switch applications.
Collector (C)	High-voltage output node	Rated for 300 V standoff; connects to RGB cathode or telephone line via current-limiting resistor or transformer primary.

Key Features

Feature	Design Value
High-voltage breakdown	V_CBO = V_CEO = 300 V enables direct interface with telecom line voltages and CRT anode-derived supplies.
Complementary pairing	Designed as NPN counterpart to STPSA92 (PNP), simplifying push-pull stage design in video and telephony circuits.
Low leakage	I_CBO ≤ 100 nA at V_CB = 200 V ensures stable bias in high-impedance video amplifier nodes over temperature.
Medium-frequency response	f_T = 50 MHz supports bandwidth-critical RGB amplification without added compensation networks.

Applications

Video Amplifier (RGB Cathode Control)

Telephone Wireline Interface

Use Scenario: Driving individual red/green/blue cathodes in CRT-based display systems with variable current modulation.

IC Role / Device Role / Timing Role: Linear current-controlled switch regulating cathode current based on analog video input level.

Use Value: 300 V V_CEO rating allows direct connection to CRT cathode supply rails; h_FE consistency ensures uniform color intensity across scan lines.

Use Scenario: Implementing hook-switch detection and dial pulse generation in analog telephone line interface cards.

IC Role / Device Role / Timing Role: High-voltage switch controlling loop current during off-hook and dialing states.

Use Value: 300 V V_CBO withstands 170 V RMS ringing voltage transients; low I_CBO prevents false hook-state detection under temperature stress.

DC-Coupled Video Output Stage

High-Voltage Signal Switching

Use Scenario: DC-coupled output buffer in professional video equipment requiring zero DC offset at load.

IC Role / Device Role / Timing Role: Emitter-follower configured transistor delivering low-output-impedance drive to coaxial cable loads.

Use Value: V_CE(sat) = 0.5 V and h_FE ≥ 25 enable precise DC-level translation without external level-shifting components.

Use Scenario: Isolating high-voltage control signals in industrial monitoring systems with mixed-signal grounding.

IC Role / Device Role / Timing Role: Level-shifting switch translating logic-level signals to 100–300 V domains.

Use Value: R_thj-amb = 200 °C/W and T_j(max) = 150 °C allow reliable pulsed operation at 0.6 A peak with <1.5% duty cycle.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC639	V_CEO = 80 V, I_C = 1 A, h_FE = 40–250 - lower voltage rating, higher current, wider gain spread.	Not suitable for 300 V telecom or CRT cathode applications; limited to low-voltage video switching or general-purpose amplification.	Select only when system voltage remains below 60 V and wide h_FE tolerance is acceptable.
MPSA42	V_CEO = 300 V, I_C = 0.5 A, h_FE = 50–250 - identical voltage/current ratings but broader h_FE range and higher f_T (300 MHz).	Compatible in most STPSA42 roles, but higher gain variability may require recalibration of base bias networks in precision video stages.	Preferred for new designs needing higher f_T; verify h_FE binning if closed-loop gain stability is critical.

Compared with BC639 and MPSA42, STPSA42 offers tighter h_FE distribution (25–40) and guaranteed 300 V breakdown in both C–B and C–E configurations, making it uniquely suited for legacy CRT and telecom designs where parameter consistency and absolute voltage margin are prioritized over raw speed or current headroom.

Availability

STPSA42 is available at Aetrix Electronics and suitable for video amplifier circuits, telephone wireline interfaces, DC-coupled video output stages, and high-voltage signal switching applications requiring stable component supply and long-term obsolescence management.

Supply support for STPSA42 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing analog, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The STPSA42 belongs to ST's legacy high-voltage bipolar transistor product line, developed specifically for analog signal conditioning and line-interface applications in telecom and display electronics where robustness and parameter consistency outweigh digital integration needs.

FAQ

Is STPSA42 still in active production?

No - STPSA42 is marked "Obsolete Product(s)" in the official STMicroelectronics preliminary data sheet dated February 2003. It is no longer manufactured, but Aetrix Electronics maintains legacy inventory and supports long-life design continuity through controlled distribution and cross-reference guidance.

What is the pin configuration for STPSA42 in TO-92 package?

Viewing the TO-92 package with flat side facing outward and leads pointing down, the pin order from left to right is Emitter (E), Base (B), Collector (C). This matches standard TO-92 NPN orientation and is confirmed by ST's mechanical drawings and schematic symbol polarity in the datasheet.

Can STPSA42 be used as a direct replacement for MPSA42?

Functionally yes in many high-voltage switching roles, but not interchangeably without validation: STPSA42 has narrower h_FE (25–40 vs. 50–250), identical V_CEO/V_CBO, and lower f_T (50 MHz vs. 300 MHz). Base resistor networks may require adjustment to ensure saturation in switching applications.

What thermal derating applies above 25 °C case temperature?

P_tot must be linearly derated above 25 °C at 5 mW/°C (based on R_thj-amb = 200 °C/W). At T_C = 75 °C, maximum allowable dissipation drops to 375 mW; forced airflow or PCB copper area must be added to maintain T_j ≤ 150 °C under sustained load.

STPSA42 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA)

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 500 mA

Voltage - Collector Emitter Breakdown (Max):: 300 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 2mA, 20mA

Current - Collector Cutoff (Max):: 100nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 30mA, 10V

Power - Max:: 625 mW

Frequency - Transition:: 50MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

STPSA42 FAQ

1.How can I place an order for STPSA42 through Aetrix?

Please submit a Request for Quotation (RFQ) for STPSA42 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for STPSA42 reliable?

The price and inventory of STPSA42 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STPSA42 is usually 5 days.

3.What payment methods are accepted for STPSA42?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STPSA42 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STPSA42?

STPSA42 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STPSA42 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for STPSA42?

For technical support, including STPSA42 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STPSA42 requirements.

6.How does Aetrix verify that STPSA42 is sourced from the original manufacturer or authorized distributors?

All STPSA42 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that STPSA42 meets industry standards.

7.What is the process for return or replacement of STPSA42?

All STPSA42 units undergo pre-shipment inspection (PSI). If there is an issue with STPSA42, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The STPSA42 part is unused and in its original packaging.

Return procedure for STPSA42:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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