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

onsemi 2SB1121S-TD-E

Name: 2SB1121S-TD-E
Brand: onsemi
SKU: 2SB1121S-TD-E
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2SB1121S-TD-E

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-243AA

Datasheet:: 2SB1121S-TD-E.pdf

Description:: TRANS PNP 25V 2A PCP

Quantity:: RFQ Add To RFQ list

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Product details

Overview

2SB1121S-TD-E from onsemi is a PNP bipolar junction transistor (BJT) designed for medium-power switching and linear amplification in compact hybrid ICs. It features V_CEO = −25 V, I_C = −2 A continuous, V_CE(sat) = −0.35 V (typ) at I_C = −1.5 A / I_B = −75 mA, f_T = 150 MHz, and operates up to T_j = 150 °C - used in relay drivers and voltage regulators.

For engineers reviewing the 2SB1121S-TD-E datasheet, pinout, applications, or equivalent options, key selection criteria include low saturation voltage, wide SOA, fast switching (t_on = 60 ns, t_f = 25 ns), PCP package thermal performance, and h_FE rank S (140–280 @ I_C = −100 mA).

Technical Context

This PNP BJT employs FBET and MBIT processes to achieve low V_CE(sat) and high current capability in a thermally efficient PCP (SC-62/SOT-89/TO-243) package. Its large safe operating area (SOA) supports pulsed I_CP = −5 A, enabling robust operation in inductive load switching.

With f_T = 150 MHz and Cob = 32 pF, the 2SB1121S-TD-E delivers high-frequency switching performance while maintaining DC gain stability: h_FE1 = 140–400 (rank-dependent) at I_C = −100 mA and h_FE2 = 65 min at I_C = −1.5 A.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	−25 V - maximum collector-emitter blocking voltage under open-base conditions; defines usable supply rail headroom in switching applications
I_C (cont.)	−2 A - continuous collector current rating; sets steady-state power handling limit with appropriate heatsinking
V_CE(sat)	−0.35 V (typ) at I_C = −1.5 A / I_B = −75 mA - enables <1.1 W conduction loss per device in high-current switch mode
f_T	150 MHz - usable bandwidth for small-signal amplification or high-speed digital switching up to ~10–20 MHz
t_on/t_f	60 ns / 25 ns - supports PWM frequencies >5 MHz with minimal switching loss in relay/lamp driver stages
P_C (ceramic)	1.3 W - thermal dissipation capacity when mounted on 250 mm² × 0.8 mm ceramic substrate; enables compact layout without forced cooling
h_FE Rank S	140–280 @ V_CE = −2 V, I_C = −100 mA - ensures predictable base drive requirements in linear regulator error amplifiers

Pinout & Package

Package: PCP (JEITA SC-62 / JEDEC TO-243AA / industry-standard SOT-89). Thermally enhanced plastic case with exposed emitter pad for improved heat transfer.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Current-controlled input node	Receives forward-biased base current to saturate or bias the PNP; requires series resistor for current limiting in digital drive
2 (Collector)	Main current sink terminal	Connected to load return path; carries full switched current; electrically tied to exposed metal tab in PCP package
3 (Emitter)	Common reference and current source	Typically connected to positive rail in high-side switch configuration; serves as thermal and electrical reference point

Key Features

Feature	Design Value
Low V_CE(sat)	−0.35 V typ at I_C = −1.5 A reduces conduction loss by >40% vs. standard PNP transistors in 24 V relay drivers
Wide SOA	Supports −5 A pulsed current with no second breakdown - critical for driving inductive loads like solenoids and contactors
Fast switching	60 ns turn-on and 25 ns fall time enable clean edge transitions in 1–5 MHz PWM lamp dimming circuits
Ultrasmall PCP package	3.0 × 1.5 × 1.0 mm footprint allows ≥30% higher component density than TO-92 in hybrid power modules
High f_T	150 MHz gain-bandwidth supports stable feedback in discrete LDO pass transistor configurations up to 100 kHz loop bandwidth

Applications

Relay Drivers	Voltage Regulators
Use Scenario: Driving 12–24 V DC electromagnetic relays in industrial PLC output modules with 100 ms coil energization cycles. IC Role / Device Role / Timing Role: High-side PNP switch controlling relay coil current path to ground; handles I_CP = −5 A surge during pull-in. Use Value: Low V_CE(sat) minimizes coil voltage drop and self-heating; wide SOA prevents failure during back-EMF transients.	Use Scenario: Discrete pass transistor in adjustable linear regulators delivering up to 1.5 A at 5–15 V output. IC Role / Device Role / Timing Role: Series pass element regulating output voltage via base-emitter control; operates in active region with V_CE ≈ 2–4 V. Use Value: High h_FE (140–280) reduces base drive burden; 150 MHz f_T ensures loop stability with minimal compensation.
Lamp Drivers	Electrical Equipment Control
Use Scenario: PWM-controlled incandescent/halogen lamp dimming in automotive interior lighting and HVAC panel backlighting. IC Role / Device Role / Timing Role: High-side switch modulating lamp current at 1–10 kHz; conducts −2 A continuous during ON phase. Use Value: Fast t_f = 25 ns eliminates visible flicker; low V_CE(sat) preserves lamp voltage headroom at low duty cycles.	Use Scenario: Load switching in programmable logic controller (PLC) digital output cards for factory automation equipment. IC Role / Device Role / Timing Role: Final-stage output transistor interfacing microcontroller GPIO to 24 V DC field devices (sensors, indicators, small actuators). Use Value: PCP package withstands industrial vibration; −25 V V_CEO accommodates 24 V nominal + 30% line surge per IEC 61000-4-5.

Relay Drivers

Voltage Regulators

Use Scenario: Driving 12–24 V DC electromagnetic relays in industrial PLC output modules with 100 ms coil energization cycles.

IC Role / Device Role / Timing Role: High-side PNP switch controlling relay coil current path to ground; handles I_CP = −5 A surge during pull-in.

Use Value: Low V_CE(sat) minimizes coil voltage drop and self-heating; wide SOA prevents failure during back-EMF transients.

Use Scenario: Discrete pass transistor in adjustable linear regulators delivering up to 1.5 A at 5–15 V output.

IC Role / Device Role / Timing Role: Series pass element regulating output voltage via base-emitter control; operates in active region with V_CE ≈ 2–4 V.

Use Value: High h_FE (140–280) reduces base drive burden; 150 MHz f_T ensures loop stability with minimal compensation.

Lamp Drivers

Electrical Equipment Control

Use Scenario: PWM-controlled incandescent/halogen lamp dimming in automotive interior lighting and HVAC panel backlighting.

IC Role / Device Role / Timing Role: High-side switch modulating lamp current at 1–10 kHz; conducts −2 A continuous during ON phase.

Use Value: Fast t_f = 25 ns eliminates visible flicker; low V_CE(sat) preserves lamp voltage headroom at low duty cycles.

Use Scenario: Load switching in programmable logic controller (PLC) digital output cards for factory automation equipment.

IC Role / Device Role / Timing Role: Final-stage output transistor interfacing microcontroller GPIO to 24 V DC field devices (sensors, indicators, small actuators).

Use Value: PCP package withstands industrial vibration; −25 V V_CEO accommodates 24 V nominal + 30% line surge per IEC 61000-4-5.

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-power switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
2SB1210S-TL-E	V_CEO = −30 V, I_C = −1.5 A, V_CE(sat) = −0.45 V (typ), same PCP package	Higher voltage margin but lower current rating; suitable where 24 V system surges exceed 25 V	Choose when V_CEO derating >20% is required; verify h_FE meets base drive budget
MMBT2907ALT1G	SOT-23 package, I_C = −600 mA, V_CE(sat) = −0.4 V (typ), f_T = 200 MHz	Lower power, smaller footprint; not suitable for >1 A loads or high-SOA demands	Select only for signal-level or low-current switching; avoid in relay/lamp drivers exceeding 0.8 A

Compared with 2SB1121S-TD-E, 2SB1210S-TL-E trades current capacity for higher voltage ruggedness, while MMBT2907ALT1G offers higher speed in a miniature package but cannot replicate the 2SB1121S-TD-E's −2 A continuous capability or wide SOA - making the latter irreplaceable in high-current industrial switching.

Availability

2SB1121S-TD-E is available at Aetrix Electronics and suitable for relay drivers, voltage regulators, and lamp drivers requiring stable component supply across industrial control, building automation, and embedded power systems.

Supply support for 2SB1121S-TD-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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier focused on energy-efficient innovation for automotive, industrial, cloud, and IoT applications.

The 2SB1121S-TD-E belongs to onsemi's general-purpose PNP BJT product line, engineered for high-density hybrid IC integration and reliable medium-power switching in space-constrained industrial equipment.

FAQ

What is the package type and pin configuration of the 2SB1121S-TD-E?

The 2SB1121S-TD-E uses the PCP package (JEITA SC-62 / JEDEC TO-243AA), identical to SOT-89. Pin 1 is Base, Pin 2 is Collector (electrically connected to the exposed metal tab), and Pin 3 is Emitter. This configuration supports high-current sinking with direct thermal path to PCB copper.

What does the "S" suffix in 2SB1121S-TD-E indicate?

Per onsemi documentation, the "S" denotes h_FE Rank S - specifying DC current gain between 140 and 280 at V_CE = −2 V and I_C = −100 mA. This rank ensures consistent base drive design across production lots of the 2SB1121S-TD-E.

Can the 2SB1121S-TD-E replace the 2SB1121T-TD-E in a design?

Yes, but only if h_FE tolerance is acceptable: the 2SB1121T-TD-E has h_FE = 200–400 (Rank T), offering higher minimum gain. The 2SB1121S-TD-E provides tighter low-end gain control (140–280), which may reduce base current variation in precision linear applications.

What is the maximum power dissipation of the 2SB1121S-TD-E on a standard FR-4 PCB?

onsemi specifies P_C = 500 mW on FR-4 (unspecified area), but recommends 1.3 W when mounted on a 250 mm² × 0.8 mm ceramic substrate. For FR-4 layouts, thermal vias under the emitter pad and ≥10 cm² copper pour are required to approach 0.8–1.0 W sustained dissipation in the 2SB1121S-TD-E.

Is the 2SB1121S-TD-E RoHS compliant and lead-free?

Yes - the "E" suffix in 2SB1121S-TD-E explicitly indicates Pb-free (lead-free) construction per J-STD-609, and the device complies with RoHS Directive 2011/65/EU. Packaging is marked "Pb-Free" and shipped in dry-packed reels per J-STD-033.

2SB1121S-TD-E Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-243AA

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 2 A

Voltage - Collector Emitter Breakdown (Max):: 25 V

Vce Saturation (Max) @ Ib, Ic:: 600mV @ 75mA, 1.5A

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 100 @ 100mA, 2V

Power - Max:: 500 mW

Frequency - Transition:: 150MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: PCP

2SB1121S-TD-E FAQ

1.How can I place an order for 2SB1121S-TD-E through Aetrix?

Please submit a Request for Quotation (RFQ) for 2SB1121S-TD-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 2SB1121S-TD-E reliable?

The price and inventory of 2SB1121S-TD-E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2SB1121S-TD-E is usually 5 days.

3.What payment methods are accepted for 2SB1121S-TD-E?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2SB1121S-TD-E transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2SB1121S-TD-E?

2SB1121S-TD-E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2SB1121S-TD-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 2SB1121S-TD-E?

For technical support, including 2SB1121S-TD-E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2SB1121S-TD-E requirements.

6.How does Aetrix verify that 2SB1121S-TD-E is sourced from the original manufacturer or authorized distributors?

All 2SB1121S-TD-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 2SB1121S-TD-E meets industry standards.

7.What is the process for return or replacement of 2SB1121S-TD-E?

All 2SB1121S-TD-E units undergo pre-shipment inspection (PSI). If there is an issue with 2SB1121S-TD-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 2SB1121S-TD-E part is unused and in its original packaging.

Return procedure for 2SB1121S-TD-E:

1.Submit a request within 90 days.

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

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