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

onsemi MJE170STU

Name: MJE170STU
Brand: onsemi
SKU: MJE170STU
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MJE170STU

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-225AA, TO-126-3

Datasheet:: MJE170STU.pdf

Description:: TRANS PNP 40V 3A TO-126-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

MJE170STU from ON Semiconductor is a PNP epitaxial silicon transistor designed for low-power audio amplification and high-speed switching applications. It features a -40 V collector-emitter breakdown voltage (V_CEO), -3 A continuous collector current (I_C), 12.5 W collector dissipation at T_C = 25°C, and DC current gain (h_FE) of 50–250 at I_C = -100 mA. It is commonly used in Class-B audio output stages and relay drivers.

For engineers reviewing the MJE170STU datasheet, pinout, applications, or equivalent options, key selection considerations include its TO-126 package thermal performance, PNP polarity compatibility with complementary driver circuits, saturation voltage behavior under pulsed loads, and safe operating area limitations at elevated case temperatures.

Technical Context

The MJE170STU operates as a medium-power PNP bipolar junction transistor with fixed emitter-base and collector-base junction structures optimized for linear amplification and switching. Its h_FE varies from 50 at I_C = -100 mA to 12 at I_C = -1.5 A, indicating strong current-dependent gain compression-critical for distortion management in audio output stages.

It exhibits V_CE(sat) = -0.3 V at I_C = -500 mA / I_B = -50 mA and rises to -1.7 V at I_C = -3 A / I_B = -600 mA, confirming its intended use in moderate-current, non-saturated switching where base drive capability must be carefully matched. Cob = 50 pF at V_CB = -10 V supports stable operation up to 50 MHz f_T.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	-40 V - Maximum allowable collector-emitter voltage before avalanche breakdown; defines safe rail voltage headroom in PNP amplifier or switch designs.
I_C (DC)	-3 A - Continuous collector current rating; sets upper limit for steady-state load handling in power stage applications.
P_C (T_C=25°C)	12.5 W - Thermal power limit at case temperature 25°C; requires heatsinking for sustained operation above ~1.5 W at ambient.
h_FE	50–250 - DC current gain range at V_CE = -1 V; determines required base drive current for target collector load across operating conditions.
V_CE(sat)	-0.3 V to -1.7 V - Collector-emitter saturation voltage across I_C = -500 mA to -3 A; directly impacts conduction loss and thermal rise in switching mode.
f_T	50 MHz - Current gain bandwidth product; supports stable audio-frequency amplification and fast digital switching up to ~5–10 MHz.

Pinout & Package

Package: TO-126 - Three-lead plastic power package with integral metal tab for mechanical mounting and thermal conduction to heatsink. Pin 1 = Emitter, Pin 2 = Collector (tab-connected), Pin 3 = Base.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current source terminal for PNP device	Connected to higher potential rail in common-emitter configuration; carries full load current and defines reference for base bias network.
2 (Collector)	Current sink terminal, electrically tied to metal tab	Must be isolated from heatsink unless circuit design permits direct connection; tab provides primary thermal path to external heatsink.
3 (Base)	Control input for minority-carrier injection	Requires current-limited drive (max I_B = -1 A); base-emitter voltage drop of -1.2 V at I_C = -500 mA informs bias resistor selection.

Key Features

Feature	Design Value
High h_FE at low current	h_FE ≥ 50 at I_C = -100 mA enables efficient low-level signal amplification without excessive base drive overhead.
Controlled saturation behavior	V_CE(sat) ≤ -0.9 V at I_C = -1.5 A ensures predictable conduction loss and thermal generation in Class-B output stages.
Low output capacitance	C_ob = 50 pF at V_CB = -10 V minimizes Miller effect and supports clean turn-off in switching applications up to 10 MHz.
Robust SOA at DC	Safe Operating Area includes DC boundary up to 3 A / 40 V, enabling reliable linear operation without secondary breakdown concerns.

Applications

Audio Power Amplifier Output Stage	DC Motor Driver Half-Bridge
Use Scenario: Used as the PNP complement in push-pull Class-B audio output stage driving 4–8 Ω speakers with ±15 V rails. IC Role / Device Role / Timing Role: PNP power transistor delivering negative half-cycle current; paired with NPN counterpart (e.g., MJE180) for symmetrical output swing. Use Value: h_FE ≥ 50 at I_C = -500 mA ensures stable biasing and low crossover distortion; V_CE(sat) = -0.3 V limits quiescent heating during mid-level output.	Use Scenario: Controls low-side current path in unidirectional 12 V DC motor interface with PWM speed control. IC Role / Device Role / Timing Role: High-current PNP switch sinking motor return current; driven by microcontroller GPIO via base resistor network. Use Value: I_C = -3 A rating handles stall currents up to 2.5 A; f_T = 50 MHz supports clean 20 kHz PWM edge transitions with minimal delay.
Relay Driver Circuit	Linear Voltage Regulator Pass Element
Use Scenario: Drives 12 V, 100 mA coil relay in industrial PLC output module with opto-isolated control input. IC Role / Device Role / Timing Role: Saturated PNP switch providing coil current path to ground; base driven by open-collector logic output. Use Value: V_CE(sat) = -0.3 V ensures >95% coil voltage delivery; Cob = 50 pF prevents false triggering from fast transients on shared PCB traces.	Use Scenario: Acts as series pass transistor in adjustable 0–12 V, 1 A linear regulator using LM317 feedback network. IC Role / Device Role / Timing Role: PNP pass element sourcing regulated output current; emitter connected to input, collector to load, base controlled by error amplifier. Use Value: P_C = 12.5 W at T_C = 25°C allows 5 W continuous dissipation with modest heatsink; h_FE stability over I_C improves regulation accuracy under load variation.

Audio Power Amplifier Output Stage

DC Motor Driver Half-Bridge

Use Scenario: Used as the PNP complement in push-pull Class-B audio output stage driving 4–8 Ω speakers with ±15 V rails.

IC Role / Device Role / Timing Role: PNP power transistor delivering negative half-cycle current; paired with NPN counterpart (e.g., MJE180) for symmetrical output swing.

Use Value: h_FE ≥ 50 at I_C = -500 mA ensures stable biasing and low crossover distortion; V_CE(sat) = -0.3 V limits quiescent heating during mid-level output.

Use Scenario: Controls low-side current path in unidirectional 12 V DC motor interface with PWM speed control.

IC Role / Device Role / Timing Role: High-current PNP switch sinking motor return current; driven by microcontroller GPIO via base resistor network.

Use Value: I_C = -3 A rating handles stall currents up to 2.5 A; f_T = 50 MHz supports clean 20 kHz PWM edge transitions with minimal delay.

Relay Driver Circuit

Linear Voltage Regulator Pass Element

Use Scenario: Drives 12 V, 100 mA coil relay in industrial PLC output module with opto-isolated control input.

IC Role / Device Role / Timing Role: Saturated PNP switch providing coil current path to ground; base driven by open-collector logic output.

Use Value: V_CE(sat) = -0.3 V ensures >95% coil voltage delivery; Cob = 50 pF prevents false triggering from fast transients on shared PCB traces.

Use Scenario: Acts as series pass transistor in adjustable 0–12 V, 1 A linear regulator using LM317 feedback network.

IC Role / Device Role / Timing Role: PNP pass element sourcing regulated output current; emitter connected to input, collector to load, base controlled by error amplifier.

Use Value: P_C = 12.5 W at T_C = 25°C allows 5 W continuous dissipation with modest heatsink; h_FE stability over I_C improves regulation accuracy under load variation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJE170G	Same die, Pb-free TO-126 package per ON Semiconductor's Green Policy; identical electrical specs and pinout.	No functional difference; suitable for RoHS-compliant production requiring lead-free finish.	Select MJE170G when environmental compliance mandates Pb-free assembly; otherwise MJE170STU remains fully interchangeable.
BD140	Lower V_CEO (-80 V vs. -40 V), lower h_FE (25–250), same TO-126 package; not pin-compatible due to reversed pin order (E-B-C vs. E-C-B).	Not suitable for direct replacement; requires PCB layout revision and bias recalibration due to pinout and gain mismatch.	Consider BD140 only in new designs where higher breakdown margin is needed and pinout can be accommodated; avoid for drop-in substitution.

Compared with MJE170STU, MJE170G offers identical performance with RoHS compliance, while BD140 provides higher voltage rating but demands board redesign and gain-aware biasing-making MJE170STU optimal for legacy audio and switching designs requiring known pinout and gain profile.

Availability

MJE170STU is available at Aetrix Electronics and suitable for audio amplifier output stages, relay driver circuits, DC motor control interfaces, and linear regulator pass elements requiring stable component supply and long-term industrial availability.

Supply support for MJE170STU 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 manufacturer specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The MJE170STU belongs to ON Semiconductor's legacy power bipolar transistor family, originally developed by Fairchild Semiconductor for general-purpose linear and switching applications demanding reliability, thermal robustness, and predictable gain characteristics.

FAQ

What is the maximum continuous collector current rating for the MJE170STU?

The MJE170STU has a maximum continuous collector current (I_C) rating of -3 A at T_C = 25°C. This rating assumes adequate heatsinking; derating is required above 25°C case temperature per the thermal resistance curve in the datasheet. At T_C = 100°C, the usable I_C drops to approximately -1.5 A. The MJE170STU must not be operated beyond this limit without verifying junction temperature via thermal modeling or measurement.

Does the MJE170STU have a built-in base-emitter resistor?

No, the MJE170STU is a standard discrete PNP bipolar transistor without any integrated base-emitter resistors. It requires an external base current limiting resistor or active driver circuit to establish proper bias conditions. The absence of internal resistors gives designers full control over base drive strength and switching speed-critical for optimizing V_CE(sat) and switching losses in the MJE170STU.

What is the pin configuration of the MJE170STU in the TO-126 package?

The MJE170STU uses the standard TO-126 pinout: Pin 1 = Emitter, Pin 2 = Collector (connected to the metal tab), Pin 3 = Base. When viewed with the flat side facing forward and leads pointing downward, the pins are numbered left-to-right as 1–2–3. This configuration is consistent across Fairchild/ON Semiconductor's MJE170-series transistors and differs from alternatives like BD140, which uses E-B-C ordering.

Can the MJE170STU be used in parallel configurations for higher current handling?

Parallel operation of MJE170STU devices is not recommended without individual emitter degeneration resistors due to gain and V_BE mismatches that cause current imbalance. Even with matched units, thermal runaway risk increases because higher current in one device raises its junction temperature, further lowering V_BE and drawing more current. For higher current needs, select a single higher-rated device rather than paralleling multiple MJE170STU units.

What is the typical base-emitter ON voltage for the MJE170STU?

The typical base-emitter ON voltage (V_BE(on)) for the MJE170STU is -1.2 V at V_CE = -1 V and I_C = -500 mA. This value is critical for calculating base resistor values in switch-mode applications and for designing bias networks in linear amplifier stages. V_BE(on) decreases slightly with increasing temperature and increases with decreasing collector current, so design margins should account for this variation across the operating range of the MJE170STU.

MJE170STU Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-225AA, TO-126-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 3 A

Voltage - Collector Emitter Breakdown (Max):: 40 V

Vce Saturation (Max) @ Ib, Ic:: 1.7V @ 600mA, 3A

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 50 @ 100mA, 1V

Power - Max:: 1.5 W

Frequency - Transition:: 50MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126-3

MJE170STU FAQ

1.How can I place an order for MJE170STU through Aetrix?

Please submit a Request for Quotation (RFQ) for MJE170STU 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 MJE170STU reliable?

The price and inventory of MJE170STU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MJE170STU is usually 5 days.

3.What payment methods are accepted for MJE170STU?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MJE170STU transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MJE170STU?

MJE170STU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MJE170STU 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 MJE170STU?

For technical support, including MJE170STU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MJE170STU requirements.

6.How does Aetrix verify that MJE170STU is sourced from the original manufacturer or authorized distributors?

All MJE170STU 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 MJE170STU meets industry standards.

7.What is the process for return or replacement of MJE170STU?

All MJE170STU units undergo pre-shipment inspection (PSI). If there is an issue with MJE170STU, 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 MJE170STU part is unused and in its original packaging.

Return procedure for MJE170STU:

1.Submit a request within 90 days.

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

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