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Diodes Incorporated ZTX857STZ
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- Part No.:
- ZTX857STZ
- Manufacturer:
- Diodes Incorporated
- Category:
- Single Bipolar Transistors
- Package:
- E-Line-3, Formed Leads
- Datasheet:
-
ZTX857STZ.pdf
- Description:
- TRANS NPN 300V 3A E-LINE
- Quantity:
- Payment:
- Shipping:
Inventory:1,971
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Product details
Overview
ZTX857STZ from Diodes Incorporated is an NPN silicon planar medium-power high-current transistor rated for 300 V VCEO, 3 A continuous collector current, and 1.2 W power dissipation at Tamb = 25°C; it delivers low saturation voltage (140 mV at IC = 2 A, IB = 200 mA) and supports switching in high-voltage industrial power supplies.
For engineers reviewing the ZTX857STZ datasheet, ZTX857STZ pinout, ZTX857STZ application, or ZTX857STZ equivalent, key selection criteria include VCEO rating, hFE consistency across 10 mA–3 A, safe operating area under pulsed conditions, and TO-92-compatible thermal derating behavior.
Technical Context
This discrete NPN bipolar junction transistor operates in linear amplification and hard-switching modes with verified breakdown performance: V(BR)CEO ≥ 300 V (IC = 10 mA), V(BR)CBO ≥ 330 V (IC = 100 µA), and V(BR)EBO ≥ 6 V (IE = 100 µA). Its fT of 80 MHz at IC = 100 mA, VCE = 10 V enables moderate-speed switching.
Thermal design relies on Rth(j-amb) = 150 °C/W (PCB-mounted, 1 in² copper) and Rth(j-case) = 50 °C/W, with transient impedance curves validated for pulse widths from 0.1 ms to 1 s. Saturation characteristics are specified under pulsed conditions (300 µs, ≤2% duty cycle).
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 300 V - Maximum collector-emitter voltage before avalanche breakdown under open-base condition. |
| IC (continuous) | 3 A - Continuous DC collector current sustainable with proper PCB heatsinking (1 in² copper). |
| VCE(sat) | 140 mV @ IC = 2 A, IB = 200 mA - Low conduction loss enabling efficient switching in 200–300 V rail applications. |
| hFE | 100–300 @ IC = 10 mA–3 A - Gain stability across three decades of collector current supports consistent drive requirements. |
| fT | 80 MHz @ IC = 100 mA, VCE = 10 V - Enables reliable operation in <100 kHz switch-mode power supply control stages. |
| Rth(j-amb) | 150 °C/W - Thermal resistance defining maximum ambient temperature rise per watt dissipated on standard FR-4 PCB. |
Pinout & Package
Package: TO-92 compatible (E-Line 3-303 outline), through-hole, epoxy-molded plastic case with leads identified as Collector (C), Base (B), Emitter (E) - pin 1 = Emitter, pin 2 = Base, pin 3 = Collector (viewed from flat side, leads down).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Emitter (pin 1) | Current sink terminal | Reference node for base drive; connects to ground or low-side return path in common-emitter configurations. |
| Base (pin 2) | Control input | Receives forward-biased current to enable conduction; requires IB ≥ IC/hFE(min) for saturation. |
| Collector (pin 3) | High-voltage output terminal | Handles up to 300 V potential swing; connects to primary-side switching node in flyback or forward converters. |
Key Features
| Feature | Design Value |
|---|---|
| High VCEO rating | 300 V enables direct use in 230 VAC rectified bus (≈325 V peak) without series stacking. |
| Low VCE(sat) | 140 mV at 2 A reduces conduction loss to <0.3 W, improving efficiency in medium-power SMPS. |
| Wide hFE range | 100–300 across 10 mA–3 A ensures predictable base drive sizing across load conditions. |
| Pulsed ICM | 5 A peak allows short-duration surge handling (e.g., inrush limiting or motor start-up). |
| TO-92 compatibility | Drop-in replacement for legacy ZTX851/ZTX853 in existing through-hole layouts with no footprint change. |
Applications
| Switch-Mode Power Supply (SMPS) Primary Switch | DC Motor Driver (Medium Power) |
|---|---|
Use Scenario: Used as main switching transistor in 20–60 W offline flyback converters with 230 VAC input. IC Role / Device Role / Timing Role: Discrete high-voltage NPN switch controlling primary winding current during ON-time; driven by UC3842/UC3843 controller. Use Value: 300 V VCEO withstands reflected flyback voltage spikes; 140 mV VCE(sat) limits conduction loss to <0.3 W at 2 A. | Use Scenario: H-bridge low-side driver stage for 24–48 V brushed DC motors drawing up to 3 A continuous. IC Role / Device Role / Timing Role: Ground-referenced current sink in half-bridge configuration; switched via microcontroller GPIO with base resistor network. Use Value: 3 A IC rating supports motor stall current; hFE ≥ 100 at 2 A ensures reliable saturation with ≤20 mA base drive. |
| High-Voltage Linear Regulator Pass Element | Industrial Relay Driver |
Use Scenario: Series pass transistor in 100–250 V adjustable linear regulators for analog instrumentation. IC Role / Device Role / Timing Role: Voltage-controlled current source operating in active region; biased with constant-current mirror. Use Value: V(BR)CEO ≥ 300 V prevents breakdown under line transients; Rth(j-amb) = 150 °C/W allows 1.2 W dissipation with minimal heatsink. | Use Scenario: Direct drive of 12–24 V industrial relays with coil currents up to 2.5 A. IC Role / Device Role / Timing Role: Single-stage saturated switch interfacing microcontroller outputs to relay coils. Use Value: Low VCE(sat) (≤170 mV) minimizes self-heating during sustained ON-state; TO-92 mounting simplifies board-level integration. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar NPN high-voltage switching transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ZTX851 | VCEO = 250 V, Ptot = 1.0 W, hFE min = 100 @ IC = 1 A | Lower voltage margin; unsuitable for 230 VAC-derived rails above 250 V peak. | Select when system max VCE < 250 V and thermal budget is tighter than 1.2 W. |
| MJD122 | TO-220 package, VCEO = 100 V, IC = 8 A, Ptot = 15 W | Higher current but lower voltage rating; requires heatsink and layout redesign. | Select only if >3 A peak current is required and voltage stress remains <100 V. |
Compared with ZTX851, ZTX857STZ provides +50 V headroom and +0.2 W power margin for 230 VAC systems; versus MJD122, it trades package size and current for voltage capability and TO-92 compatibility-critical for space-constrained, high-voltage designs.
Availability
ZTX857STZ is available at Aetrix Electronics and suitable for industrial power supplies, DC motor controllers, and high-voltage linear regulators requiring stable component supply and long-term manufacturability.
Supply support for ZTX857STZ 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
Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design centers across Asia and manufacturing in China, Taiwan, and the US.
ZTX857STZ belongs to the ZTX high-voltage transistor family, engineered specifically for robust switching and linear operation in industrial power conversion where reliability at elevated voltage and temperature is critical.
FAQ
What is the maximum safe operating voltage for ZTX857STZ in continuous DC applications?
The absolute maximum collector-emitter voltage is 300 V under open-base conditions (V(BR)CEO). For reliable long-term operation, design margins should limit steady-state VCE to ≤240 V to accommodate transients and temperature derating. The device has been validated to sustain 330 V in pulsed mode (IC = 10 mA, Tamb = 25°C).
Can ZTX857STZ be used in parallel for higher current handling?
No-ZTX857STZ lacks built-in emitter ballasting or matched gain characteristics required for stable current sharing. Parallel operation risks thermal runaway due to positive temperature coefficient of VBE(sat) and hFE variation. For >3 A, select a single higher-rated device like MJD127 or use external emitter resistors with careful thermal coupling.
What is the recommended PCB layout for thermal management?
Mount ZTX857STZ on FR-4 with ≥1 in² (6.5 cm²) of 2-oz copper connected directly to the collector pad (pin 3) via multiple thermal vias. Avoid isolation gaps near the collector lead. Keep base and emitter traces short and wide to minimize inductance in switching applications. Derate power linearly above 25°C ambient using the 150 °C/W Rth(j-amb) curve.
Does ZTX857STZ meet RoHS and REACH compliance?
Yes-ZTX857STZ is RoHS 2011/65/EU compliant and REACH SVHC-free per Diodes Incorporated's official product change notice (PCN #19-0037). Lead finish is matte tin, and the epoxy molding compound meets UL94 V-0 flammability rating. Full compliance documentation is available upon request from Aetrix Electronics.
ZTX857STZ Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Diodes Incorporated
- Series:
- -
- Package/Case:
- E-Line-3, Formed Leads
- Packaging:
- Cut Tape (CT)
- Product Status:
- Active
- Transistor Type:
- NPN
- Current - Collector (Ic) (Max):
- 3 A
- Voltage - Collector Emitter Breakdown (Max):
- 300 V
- Vce Saturation (Max) @ Ib, Ic:
- 250mV @ 600mA, 3A
- Current - Collector Cutoff (Max):
- 1µA (ICBO)
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 100 @ 500mA, 10V
- Power - Max:
- 1.2 W
- Frequency - Transition:
- 80MHz
- Operating Temperature:
- -55°C ~ 200°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- E-Line (TO-92 compatible)
ZTX857STZ FAQ
1.How can I place an order for ZTX857STZ through Aetrix?
Please submit a Request for Quotation (RFQ) for ZTX857STZ 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 ZTX857STZ reliable?
The price and inventory of ZTX857STZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZTX857STZ is usually 5 days.
3.What payment methods are accepted for ZTX857STZ?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZTX857STZ transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for ZTX857STZ?
ZTX857STZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your ZTX857STZ 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 ZTX857STZ?
For technical support, including ZTX857STZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZTX857STZ requirements.
6.How does Aetrix verify that ZTX857STZ is sourced from the original manufacturer or authorized distributors?
All ZTX857STZ 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 ZTX857STZ meets industry standards.
7.What is the process for return or replacement of ZTX857STZ?
All ZTX857STZ units undergo pre-shipment inspection (PSI). If there is an issue with ZTX857STZ, 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 ZTX857STZ part is unused and in its original packaging.
Return procedure for ZTX857STZ:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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