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onsemi TIP121TU
- Part No.:
- TIP121TU
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-220-3
- Datasheet:
-
TIP121TU.pdf
- Description:
- TRANS NPN DARL 80V 5A TO-220-3
- Quantity:
- Payment:
- Shipping:
Inventory:1,421
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Product details
Overview
TIP121TU from onsemi is an NPN silicon Darlington transistor in TO-220AB package, designed for medium-power linear amplification and low-speed switching. It delivers 5.0 A continuous collector current, 80 Vdc collector-emitter sustaining voltage (VCEO(sus)), and typical DC current gain (hFE) of 2500 at IC = 4.0 A - enabling robust drive capability in motor control and relay driver circuits.
For engineers reviewing the TIP121TU datasheet, pinout, applications, or equivalent options, key selection considerations include its built-in base-emitter shunt resistors, 65 W power dissipation at TC = 25°C, thermal resistance RJC = 1.92°C/W, and safe operating area limited by second breakdown and junction temperature.
Technical Context
The TIP121TU integrates two cascaded NPN transistors monolithically with internal base-emitter shunt resistors (≈8.0 kΩ and ≈120 Ω), eliminating external bias components. Its high hFE enables direct microcontroller GPIO drive without additional pre-driver stages.
It operates within –65°C to +150°C junction temperature range, supports unclamped inductive load energy up to 50 mJ, and exhibits VCE(sat) ≤ 2.0 V at IC = 3.0 A / IB = 12 mA - confirming suitability for saturated-switching applications requiring low conduction loss.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO(sus) | 80 Vdc minimum - sustains 80 V across C–E at IC = 100 mA with zero base drive, defining maximum off-state blocking capability. |
| IC (Continuous) | 5.0 Adc - supports sustained 5 A collector current with heatsink at TC = 25°C, enabling use in 50–100 W load interfaces. |
| hFE (Typ) | 2500 @ IC = 4.0 A - reduces required base drive current to ~1.6 mA for full 4 A output, easing MCU-level control. |
| VCE(sat) (Max) | 2.0 V @ IC = 3.0 A / IB = 12 mA - limits conduction power loss to ≤6 W at 3 A, critical for thermal management in sealed enclosures. |
| PD @ TC = 25°C | 65 W - defines maximum steady-state power dissipation with case temperature maintained at 25°C via heatsink. |
| RJC | 1.92 °C/W - quantifies thermal path resistance from junction to case; used with heatsink RCA to calculate max allowable ambient temperature. |
| E (Unclamped) | 50 mJ - specifies maximum energy the device can safely absorb during inductive turn-off without secondary breakdown. |
Pinout & Package
Package: TO-220AB (Case 221A), 3-terminal variant (Style 1), with metal tab electrically connected to collector. Mounting hole accommodates M3 screw; tab must be insulated if not referenced to system ground.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (Base) | Control input node | Receives base current to initiate conduction; internal shunt resistor provides turn-off path - no external pull-down required. |
| 2 (Collector) | Main power output terminal | Connected to metal tab; must be electrically isolated from heatsink unless circuit reference permits common-collector configuration. |
| 3 (Emitter) | Power return path | Serves as low-side switch return; carries full load current and defines emitter-referenced control logic level. |
| 4 (Collector) | Redundant collector connection | Second collector pin improves current sharing and thermal distribution; must be bonded to same net as Pin 2. |
Key Features
| Feature | Design Value |
|---|---|
| Monolithic Darlington pair | Integrates driver and output transistors on one die with matched thermal characteristics, ensuring stable gain and reduced propagation delay vs discrete pairs. |
| Built-in base-emitter shunt resistors | ≈8.0 kΩ + ≈120 Ω network ensures reliable turn-off without external components, reducing BOM count and PCB space in relay/motor drivers. |
| High VCEO(sus) rating | 80 Vdc minimum enables direct interface with 24 V industrial buses and 48 V telecom supplies while maintaining margin against inductive kickback. |
| Second-breakdown-limited SOA | Safe operating area validated for single-pulse conditions up to 100 µs - supports solenoid and lamp surge-current handling without derating. |
| Pb-free packaging | TU suffix denotes RoHS-compliant, lead-free TO-220AB construction per onsemi's Pb-Free strategy, compatible with standard reflow profiles. |
Applications
| DC Motor Control | Relay Driver Circuit |
|---|---|
|
Use Scenario: Driving 24 V, 3 A brushed DC motors in industrial actuators with PWM frequency ≤ 5 kHz. IC Role / Device Role / Timing Role: Low-side switching element providing saturated conduction and fast turn-off via internal shunt resistors. Use Value: Eliminates need for external flyback diode snubbing in many cases due to 50 mJ unclamped inductive energy rating. |
Use Scenario: Replacing mechanical relays in programmable logic controller (PLC) output modules rated for 24 V/5 A loads. IC Role / Device Role / Timing Role: Solid-state switch replacing electromechanical contacts, controlled directly by 5 V TTL logic. Use Value: Achieves >1 million operations lifetime vs relay wear-out, with 2.0 VCE(sat) limiting heat generation at full 3 A load. |
| Lamp Dimming Interface | Linear Regulator Pass Element |
|
Use Scenario: Phase-angle dimming of incandescent lamps in building automation systems using triac-triggered gate drive. IC Role / Device Role / Timing Role: Current amplifier stage boosting microcontroller output to drive triac gate with ≥50 mA peak current. Use Value: High hFE of 2500 allows 20 µA MCU output to deliver 50 mA gate current - enabling direct GPIO control without buffer ICs. |
Use Scenario: Pass transistor in adjustable 0–30 V, 3 A linear power supply with thermal foldback protection. IC Role / Device Role / Timing Role: Series pass element dissipating up to 65 W with external heatsink and current-limiting feedback. Use Value: RJC = 1.92°C/W enables stable operation at TJ ≤ 150°C with 40°C/W heatsink, supporting continuous 3 A output at 10 V drop. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar NPN Darlington transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| TIP122 | Higher VCEO(sus) = 100 Vdc; otherwise identical pinout, gain, and saturation voltage. | Required where bus voltage exceeds 80 V or higher inductive energy margin is needed. | Select TIP122 only if design requires >80 V blocking - TIP121TU offers optimal cost/performance for 24–48 V systems. |
| BD679A | TO-126 package; lower PD = 40 W; VCEO(sus) = 80 Vdc; hFE = 750 (min) - less gain, smaller footprint. | Suitable for space-constrained PCBs where 3 A max current suffices and heatsinking is limited. | Choose BD679A when board area is critical and thermal budget allows lower power dissipation; not a drop-in replacement due to package and gain differences. |
Compared with TIP122 and BD679A, the TIP121TU balances 80 V blocking, 5 A current, 65 W dissipation, and TO-220 thermal performance - making it the preferred choice for industrial 24/48 V switching where reliability and serviceability outweigh miniaturization goals.
Availability
TIP121TU is available at Aetrix Electronics and suitable for DC motor control, relay driver circuits, lamp dimming interfaces, and linear regulator pass elements requiring stable component supply and long-term industrial availability.
Supply support for TIP121TU 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 specializing in energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and consumer markets.
The TIP121TU belongs to onsemi's legacy plastic medium-power complementary silicon transistor family, engineered for robustness in general-purpose amplifier and low-speed switching applications where simplicity, thermal resilience, and proven field reliability are prioritized.
FAQ
What is the maximum continuous collector current rating for the TIP121TU?
The TIP121TU is rated for 5.0 Adc continuous collector current at case temperature TC = 25°C with adequate heatsinking. Derating applies above 25°C at 0.52 W/°C. This rating assumes proper mounting to a heatsink capable of maintaining the case temperature within specification - exceeding 5 A risks thermal runaway or second breakdown.
Does the TIP121TU require an external base resistor for microcontroller drive?
The TIP121TU incorporates built-in base-emitter shunt resistors (≈8.0 kΩ and ≈120 Ω), so no external base resistor is required for basic turn-on/turn-off control. However, a series current-limiting resistor is still recommended between the MCU GPIO and the base pin to prevent excessive base current during transient conditions or logic overvoltage events.
What is the collector-emitter saturation voltage of the TIP121TU under typical operating conditions?
The TIP121TU has a maximum VCE(sat) of 2.0 Vdc at IC = 3.0 Adc and IB = 12 mAdc. At higher currents like 5.0 Adc, VCE(sat) rises to 4.0 Vdc max. These values define conduction losses - e.g., 6 W dissipation at 3 A - and inform heatsink sizing and efficiency calculations in switching designs.
Can the TIP121TU be used in linear regulator applications?
Yes, the TIP121TU is suitable as a pass transistor in linear regulators due to its 65 W power dissipation rating at TC = 25°C, 80 VCEO(sus), and stable hFE. It must be mounted on a heatsink sized using RJC = 1.92°C/W and ambient thermal resistance to maintain TJ ≤ 150°C. Internal shunt resistors also aid stability in feedback-controlled configurations.
Is the TIP121TU pin-compatible with other devices in the TIP12x family?
Yes, the TIP121TU shares identical TO-220AB pinout (Style 1: Base–Collector–Emitter–Collector) with all TIP120, TIP121, TIP122, TIP125, TIP126, and TIP127 variants. This allows direct substitution within the same NPN group (TIP120/TIP121/TIP122) when voltage and gain requirements align - though VCEO(sus) differs across models (60/80/100 V).
TIP121TU Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-220-3
- Packaging:
- Tube
- Product Status:
- Obsolete
- Transistor Type:
- NPN - Darlington
- Current - Collector (Ic) (Max):
- 5 A
- Voltage - Collector Emitter Breakdown (Max):
- 80 V
- Vce Saturation (Max) @ Ib, Ic:
- 4V @ 20mA, 5A
- Current - Collector Cutoff (Max):
- 500µA
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 1000 @ 3A, 3V
- Power - Max:
- 2 W
- Frequency - Transition:
- -
- Operating Temperature:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- TO-220-3
TIP121TU FAQ
1.How can I place an order for TIP121TU through Aetrix?
Please submit a Request for Quotation (RFQ) for TIP121TU 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 TIP121TU reliable?
The price and inventory of TIP121TU are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for TIP121TU is usually 5 days.
3.What payment methods are accepted for TIP121TU?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for TIP121TU transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for TIP121TU?
TIP121TU orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your TIP121TU 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 TIP121TU?
For technical support, including TIP121TU datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your TIP121TU requirements.
6.How does Aetrix verify that TIP121TU is sourced from the original manufacturer or authorized distributors?
All TIP121TU 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 TIP121TU meets industry standards.
7.What is the process for return or replacement of TIP121TU?
All TIP121TU units undergo pre-shipment inspection (PSI). If there is an issue with TIP121TU, 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 TIP121TU part is unused and in its original packaging.
Return procedure for TIP121TU:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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