Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

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

STMicroelectronics STPSA42-AP

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

Compare

Part No.:: STPSA42-AP

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: STPSA42-AP.pdf

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

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:9,090

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

STPSA42-AP 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. It serves as cathode current controller in RGB video amplifier circuits and hook-switch/dialer stages in telephone wireline interfaces.

For engineers reviewing the STPSA42-AP datasheet, STPSA42-AP pinout, STPSA42-AP application, or STPSA42-AP equivalent, key selection criteria include high-voltage breakdown capability (300 V), low saturation voltage (V_CE(sat) = 0.5 V @ 20 mA/2 mA), DC current gain (h_FE ≥ 25 @ 1 mA), transition frequency (f_T = 50 MHz), and TO-92 through-hole compatibility for legacy telecom and analog video designs.

Technical Context

This NPN 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 enable direct interface with CRT anode supplies and telephone line ringing voltages.

The device exhibits low junction-to-case thermal resistance (83.3 °C/W) and operates up to 150 °C junction temperature, supporting reliable performance in thermally constrained through-hole PCB layouts. Capacitance values (C_CBO = 6 pF, C_EBO = 22 pF) support bandwidth-critical video amplification without excessive phase shift.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CBO	300 V - Enables safe operation in 200–250 V peak line-signal environments like telephone ring detection.
V_CEO	300 V - Supports direct connection to CRT anode supplies or off-hook telephone line voltages without external clamping.
I_C	0.5 A continuous - Sufficient for RGB cathode drive and hook-switch actuation in analog telephony hardware.
V_CE(sat)	0.5 V @ 20 mA/2 mA - Minimizes power loss and self-heating during saturated switching in dialer logic stages.
h_FE	25–40 @ 1–30 mA - Provides predictable DC gain across operating range for stable biasing in video amplifier feedback loops.
f_T	50 MHz @ 10 mA/20 V - Ensures adequate bandwidth for baseband video signals and pulse-dial tone generation.
R_thj-case	83.3 °C/W - Allows effective heat conduction to PCB copper pour or heatsink tab in TO-92 mounting.

Pinout & Package

STPSA42-AP uses the standard TO-92 through-hole package with lead configuration: Emitter (pin 1), Base (pin 2), Collector (pin 3), viewed from flat side with leads down. Package dimensions conform to JEDEC TO-92 outline (A = 4.32–4.95 mm, L = 12.70–15.49 mm).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current sink terminal	Connected to ground or low-impedance return path; supports 0.5 A continuous current with minimal voltage drop.
Pin 2 (Base)	Control input	Receives 2 mA drive current to saturate transistor; requires ≤ 0.9 V V_BE(sat) for full turn-on.
Pin 3 (Collector)	High-voltage output node	Handles up to 300 V reverse bias; connects to CRT anode, telephone line, or video load resistor.

Key Features

Feature	Design Value
High-voltage blocking	300 V V_CBO/V_CEO enables direct interface with telecom and CRT supply rails without external protection.
Low saturation voltage	V_CE(sat) = 0.5 V ensures <10 mW dissipation at 20 mA, reducing thermal stress in densely packed analog boards.
Stable DC gain	h_FE ≥ 25 over 1–30 mA allows consistent bias design across production lots and temperature ranges.
High-frequency response	f_T = 50 MHz supports accurate reproduction of composite video edges and dual-tone multi-frequency (DTMF) signals.
TO-92 mechanical compatibility	Standard footprint and lead spacing simplify replacement in legacy repair and rework of telecom/video equipment.

Applications

RGB Video Amplifier

Telephone Hook Switch

Use Scenario: Driving red/green/blue cathodes in analog CRT monitors to control beam intensity.

IC Role / Device Role / Timing Role: NPN current switch regulating cathode current per color channel with precise DC gain and low V_CE(sat).

Use Value: Maintains color fidelity by minimizing saturation-induced nonlinearity and enabling fast pixel transitions via 50 MHz f_T.

Use Scenario: Detecting and controlling off-hook state in POTS telephone handsets and base stations.

IC Role / Device Role / Timing Role: High-voltage NPN switch interfacing 48 V talk battery and 90 V AC ring signal to microcontroller GPIO.

Use Value: Withstands 300 V breakdown while delivering clean on/off transitions for reliable hook-state sensing and dial pulse generation.

Telephone Dialer Circuit

Line Interface Protection Stage

Use Scenario: Generating pulse-dial sequences by switching loop current in rotary-dial telephones.

IC Role / Device Role / Timing Role: Current-controlled switch sourcing up to 0.5 A loop current with defined V_CE(sat) and thermal margin.

Use Value: Delivers repeatable 10–20 ms pulse widths and stable contact closure timing due to predictable h_FE and low thermal drift.

Use Scenario: Front-end protection stage isolating sensitive line drivers from transient surges on telephone wiring.

IC Role / Device Role / Timing Role: High-voltage clamp and current limiter placed between line transformer and IC driver.

Use Value: Absorbs 200 V transients without latch-up using 300 V V_CBO, while low C_CBO (6 pF) preserves signal integrity up to 10 MHz.

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
STPSA43	V_CBO/V_CEO = 350 V; h_FE min = 40 @ 10 mA; same TO-92 package	Higher voltage margin suits newer telecom systems with elevated ring voltage specs	Select when >300 V headroom is required and higher gain improves bias stability
BCP56-16	V_CBO = 80 V; SOT-223 surface-mount; h_FE = 100–250; P_tot = 1.5 W	Not suitable for 300 V line interfaces; intended for low-voltage switching in modern PCBs	Use only in new designs where voltage requirements are ≤ 80 V and SMT assembly is mandatory

Compared with STPSA42-AP, STPSA43 offers enhanced voltage safety margin and higher gain but identical form factor, whereas BCP56-16 trades voltage capability for surface-mount compatibility and higher power handling-making it unsuitable as a drop-in replacement in legacy high-voltage through-hole systems.

Availability

STPSA42-AP is available at Aetrix Electronics and suitable for video amplifier circuits, telephone wireline interfaces, dialer modules, and legacy CRT display subsystems requiring stable component supply and long-term obsolescence management.

Supply support for STPSA42-AP 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, digital, and mixed-signal ICs for automotive, industrial, and consumer markets.

The STPSA series targets high-voltage discrete transistors for analog signal conditioning and power switching in legacy telecom, broadcast, and display equipment where reliability under sustained DC stress is critical.

FAQ

Is STPSA42-AP still in active production?

No-STPSA42-AP is marked "Obsolete Product(s)" in the official STMicroelectronics preliminary data sheet dated February 2003. Aetrix Electronics maintains limited legacy stock and supports continuity sourcing for end-of-life replacement in certified repair and maintenance programs.

What is the difference between STPSA42 and STPSA42-AP?

STPSA42 is supplied in bulk TO-92 packaging, while STPSA42-AP uses ammopack (tape-and-reel compatible carrier tape). Both share identical electrical specifications, marking ("PSA42"), and mechanical dimensions per the TO-92 ammopack mechanical drawing in the datasheet.

Can STPSA42-AP replace BC337 in a circuit?

No-BC337 has V_CEO = 45 V and I_C = 0.5 A, making it unsafe for 300 V applications. STPSA42-AP's 300 V rating is essential for telephone line and CRT use cases; substituting BC337 risks immediate breakdown and catastrophic failure.

Does STPSA42-AP require a heatsink in normal operation?

Not typically-its 625 mW total dissipation at T_C = 25 °C and R_thj-case = 83.3 °C/W allow safe operation up to ~520 mW at ambient with standard PCB copper area. Heatsinking is only needed if case temperature exceeds 25 °C or power approaches 625 mW continuously.

STPSA42-AP Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tape & Box (TB)

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-92AP

STPSA42-AP FAQ

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

Please submit a Request for Quotation (RFQ) for STPSA42-AP 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-AP reliable?

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

3.What payment methods are accepted for STPSA42-AP?

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

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STPSA42-AP?

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

Once your STPSA42-AP 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-AP?

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

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

All STPSA42-AP 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-AP meets industry standards.

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

All STPSA42-AP units undergo pre-shipment inspection (PSI). If there is an issue with STPSA42-AP, 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-AP part is unused and in its original packaging.

Return procedure for STPSA42-AP:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-09 Counterfeit Electronic Components: How to Detect, Authenticate, and Test Suspect Parts

Counterfeit components can hide behind convincing markings and passing basic function tests. This engineering reference covers source traceability, external inspection, X-ray, XRF, electrical testing, …

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…