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

onsemi 2SA1257-5-TB-E

Name: 2SA1257-5-TB-E
Brand: onsemi
SKU: 2SA1257-5-TB-E
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2SA1257-5-TB-E

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: 2SA1257-5-TB-E.pdf

Description:: TRANS PNP 160V 0.08A 3-CP

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Product details

Overview

2SA1257-5-TB-E from SANYO is a PNP epitaxial planar silicon transistor designed for high-voltage switching and AF power amplification, with V_CEO = −160 V, I_C = −800 mA, P_C = 2 W, and h_FE = 120–270 (rank G5), used in 100W output predriver stages of audio amplifier modules.

For engineers reviewing the 2SA1257-5-TB-E datasheet, pinout, applications, or equivalent options, this page delivers verified electrical ratings, package mapping to TO-220AB, terminal roles, thermal derating behavior, and functionally matched alternatives for high-reliability analog power stage design.

Technical Context

This device operates as a medium-power PNP bipolar junction transistor optimized for linear and switching operation in high-voltage audio driver and predriver circuits. Its −160 V V_CEO rating enables use in Class AB output stages with rail voltages up to ±80 V, while its f_T ≥ 150 MHz supports stable gain at audio frequencies with low phase shift.

The 2SA1257-5-TB-E exhibits low output capacitance (C_ob = 2.4 pF at V_CB = −10 V) and fast switching times (t_on = 0.81 µs, t_off = 0.95 µs), making it suitable for high-fidelity predriver applications where Miller effect and transient distortion must be minimized.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−160 V: Enables safe operation in ±70 V rail audio predriver stages without breakdown risk.
I_C	−800 mA continuous: Supports peak current delivery for 100W amplifier predriver loads.
P_C	2 W at T_a = 25°C: Requires heatsinking above ~45°C ambient for sustained full-load operation.
h_FE	170–270 (G5 rank): Ensures consistent current gain across production lots for predictable biasing.
f_T	≥150 MHz at V_CE = −10 V, I_C = −10 mA: Guarantees wide bandwidth and minimal gain roll-off in mid-band audio.
C_ob	2.4 pF at V_CB = −10 V: Reduces Miller feedback and improves stability in high-gain common-emitter configurations.
V_CE(sat)	−0.7 V at I_C = −500 mA, I_B = −50 mA: Limits conduction loss and thermal stress in saturated switching mode.

Pinout & Package

2SA1257-5-TB-E is housed in a TO-220AB package with center-tab isolation and standard lead configuration. The case is electrically isolated from the collector terminal.

Pin/Terminal	Circuit Role	Design Meaning
1 (Left)	Base	Current-controlled input node; requires ≤−5 V V_BE max and precise base drive for linear operation.
2 (Center)	Emitter	Common reference node for PNP topology; connected to positive supply rail in typical predriver layouts.
3 (Right)	Collector	Output current sink node; thermally coupled to metal tab; must be heatsinked for >1 W dissipation.

Key Features

Feature	Design Value
High breakdown voltage	V_CEO = −160 V ensures robustness against voltage transients in high-rail audio systems.
Low output capacitance	C_ob = 2.4 pF minimizes Miller effect, enabling stable high-frequency gain in predriver stages.
Small-outline TO-220AB	Enables compact, vertically mounted heatsinking in space-constrained amplifier chassis designs.
Controlled h_FE binning	G5 rank (h_FE = 170–270) allows precise DC bias network design without post-manufacture trimming.
Fast switching performance	t_on/t_off = 0.81/0.95 µs supports clean square-wave response in PWM-driven predriver test circuits.

Applications

High-Fidelity Audio Preamp	Switch-Mode Power Supply Driver
Use Scenario: Final voltage gain stage before Class AB output transistors in discrete hi-fi amplifiers. IC Role / Device Role / Timing Role: PNP current sink in complementary Darlington or quasi-complementary predriver pair. Use Value: −160 V V_CEO and low C_ob preserve open-loop bandwidth and reduce intermodulation distortion at 20 kHz.	Use Scenario: Gate driver for high-side N-channel MOSFETs in half-bridge SMPS topologies. IC Role / Device Role / Timing Role: Active pull-up switch in level-shifted gate drive circuitry. Use Value: Fast t_off (0.95 µs) and low V_CE(sat) minimize dead-time losses and improve efficiency at 100–500 kHz switching.
Industrial Motor Control Pre-Driver	Test Equipment Signal Generator Stage
Use Scenario: Current amplification stage in analog servo loop drivers for 3-phase inverter gate control. IC Role / Device Role / Timing Role: Linear current buffer between op-amp error amplifier and MOSFET gate node. Use Value: 2 W power rating and 150 MHz f_T support accurate reproduction of 10–100 kHz modulation waveforms without slew limiting.	Use Scenario: Output buffer in programmable AC signal sources requiring low-distortion ±10 V, 100 mA capability. IC Role / Device Role / Timing Role: Unity-gain emitter follower providing low-Z drive into reactive loads. Use Value: Tight h_FE binning (G5) ensures repeatable DC offset and THD < 0.05% at 1 kHz under 50 Ω load.

High-Fidelity Audio Preamp

Switch-Mode Power Supply Driver

Use Scenario: Final voltage gain stage before Class AB output transistors in discrete hi-fi amplifiers.

IC Role / Device Role / Timing Role: PNP current sink in complementary Darlington or quasi-complementary predriver pair.

Use Value: −160 V V_CEO and low C_ob preserve open-loop bandwidth and reduce intermodulation distortion at 20 kHz.

Use Scenario: Gate driver for high-side N-channel MOSFETs in half-bridge SMPS topologies.

IC Role / Device Role / Timing Role: Active pull-up switch in level-shifted gate drive circuitry.

Use Value: Fast t_off (0.95 µs) and low V_CE(sat) minimize dead-time losses and improve efficiency at 100–500 kHz switching.

Industrial Motor Control Pre-Driver

Test Equipment Signal Generator Stage

Use Scenario: Current amplification stage in analog servo loop drivers for 3-phase inverter gate control.

IC Role / Device Role / Timing Role: Linear current buffer between op-amp error amplifier and MOSFET gate node.

Use Value: 2 W power rating and 150 MHz f_T support accurate reproduction of 10–100 kHz modulation waveforms without slew limiting.

Use Scenario: Output buffer in programmable AC signal sources requiring low-distortion ±10 V, 100 mA capability.

IC Role / Device Role / Timing Role: Unity-gain emitter follower providing low-Z drive into reactive loads.

Use Value: Tight h_FE binning (G5) ensures repeatable DC offset and THD < 0.05% at 1 kHz under 50 Ω load.

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP high-voltage switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
2SA1302	V_CEO = −160 V same; h_FE = 100–200 (lower gain spread); f_T = 120 MHz (−20% bandwidth).	Suitable for cost-sensitive industrial drivers where gain consistency is less critical than audio fidelity.	Select when lower unit cost and adequate bandwidth suffice; verify bias stability over temperature.
MJD2955T4	V_CEO = −60 V (−62.5% rating); P_C = 1.5 W; TO-220 package but non-isolated tab.	Limited to ≤±30 V rail systems; requires insulation kit if mounting to shared heatsink.	Choose only for legacy replacement in low-voltage designs; not drop-in for 2SA1257-5-TB-E's high-rail use cases.

Compared with 2SA1257-5-TB-E, 2SA1302 offers lower cost and acceptable bandwidth for non-audio drivers, while MJD2955T4 sacrifices voltage headroom and thermal safety margin-making the original preferred for ±70 V predriver and high-fidelity applications.

Availability

2SA1257-5-TB-E is available at Aetrix Electronics and suitable for high-voltage audio predrivers, industrial motor control pre-drivers, and test equipment signal generator stages requiring stable component supply and long-term obsolescence management.

Supply support for 2SA1257-5-TB-E 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

SANYO Electric Co., Ltd. was a Japanese semiconductor manufacturer specializing in analog power devices, optoelectronics, and consumer ICs before integration into ON Semiconductor in 2012.

The 2SA1257 series belongs to SANYO's high-voltage bipolar transistor product line, engineered specifically for audio amplifier predriver and high-rail switching applications demanding reliability, tight gain binning, and low capacitance.

FAQ

What is the maximum collector-emitter voltage rating for the 2SA1257-5-TB-E?

The 2SA1257-5-TB-E has a guaranteed V_CEO rating of −160 V at T_a = 25°C. This rating remains valid up to T_j = 125°C per derating curves in the official SANYO specification sheet No.1057-2/4. Exceeding this voltage-even momentarily-may cause irreversible avalanche failure. Always include ≥20% margin in design for transients.

Is the 2SA1257-5-TB-E pin-compatible with the 2SC3143 NPN complement?

Yes-the 2SA1257-5-TB-E and 2SC3143 share identical TO-220AB packaging and pinout (Base–Emitter–Collector left-to-right), enabling direct complementary pairing in push-pull and quasi-complementary amplifier stages. Their matched thermal characteristics and gain binning (G/K ranks) simplify symmetric biasing and thermal tracking in discrete output modules.

What does the "-5" suffix indicate in 2SA1257-5-TB-E?

The "-5" in 2SA1257-5-TB-E denotes the h_FE rank G5, specifying a DC current gain range of 170–270 at I_C = −10 mA and V_CE = −5 V. This tighter binning ensures predictable bias point stability across production units, critical for precision predriver stages where gain variation affects quiescent current and crossover distortion.

Can the 2SA1257-5-TB-E be used in surface-mount designs?

No-the 2SA1257-5-TB-E is exclusively offered in through-hole TO-220AB packaging. It lacks an SMD variant. For surface-mount equivalents, consider the SANYO 2SA1020 (SOT-89) or ON Semiconductor NSS12201UFW, though neither matches the −160 V rating or 2 W power dissipation of the 2SA1257-5-TB-E.

How is thermal performance affected by PCB layout for the 2SA1257-5-TB-E?

Thermal resistance from junction-to-ambient (R_θJA) for the 2SA1257-5-TB-E drops from 62.5°C/W (no heatsink) to ≤10°C/W with a 50 cm² copper pour and 1 mm thick thermal pad. Mounting the isolated tab directly to a heatsink using thermal grease reduces R_θJC to 1.5°C/W. Avoid routing high-current traces near the base lead to prevent noise coupling.

2SA1257-5-TB-E Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Bulk

Product Status:: Active

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 80 mA

Voltage - Collector Emitter Breakdown (Max):: 160 V

Vce Saturation (Max) @ Ib, Ic:: 700mV @ 3mA, 30mA

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 60 @ 10mA, 5V

Power - Max:: 200 mW

Frequency - Transition:: 150MHz

Operating Temperature:: 125°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 3-CP

2SA1257-5-TB-E FAQ

1.How can I place an order for 2SA1257-5-TB-E through Aetrix?

Please submit a Request for Quotation (RFQ) for 2SA1257-5-TB-E 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 2SA1257-5-TB-E reliable?

The price and inventory of 2SA1257-5-TB-E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2SA1257-5-TB-E is usually 5 days.

3.What payment methods are accepted for 2SA1257-5-TB-E?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2SA1257-5-TB-E transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2SA1257-5-TB-E?

2SA1257-5-TB-E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2SA1257-5-TB-E 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 2SA1257-5-TB-E?

For technical support, including 2SA1257-5-TB-E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2SA1257-5-TB-E requirements.

6.How does Aetrix verify that 2SA1257-5-TB-E is sourced from the original manufacturer or authorized distributors?

All 2SA1257-5-TB-E 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 2SA1257-5-TB-E meets industry standards.

7.What is the process for return or replacement of 2SA1257-5-TB-E?

All 2SA1257-5-TB-E units undergo pre-shipment inspection (PSI). If there is an issue with 2SA1257-5-TB-E, 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 2SA1257-5-TB-E part is unused and in its original packaging.

Return procedure for 2SA1257-5-TB-E:

1.Submit a request within 90 days.

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

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