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

Diodes Incorporated ZTX688B

Name: ZTX688B
Brand: Diodes Incorporated
SKU: ZTX688B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZTX688B

Manufacturer:: Diodes Incorporated

Category:: Single Bipolar Transistors

Package:: E-Line-3

Datasheet:: ZTX688B.pdf

Description:: TRANS NPN 12V 3A E-LINE

Quantity:: RFQ Add To RFQ list

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Inventory:2,669

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Product details

Overview

ZTX688B from Diodes Incorporated is an NPN silicon planar medium-power high-gain transistor with V_CEO = 12 V, h_FE = 400 at I_C = 3 A, and V_CE(sat) as low as 0.04 V at I_C = 0.1 A / I_B = 1 mA - optimized for high-efficiency switching in battery-powered motor drivers and flash gun converters.

For engineers reviewing the ZTX688B datasheet, ZTX688B pinout, ZTX688B application, or ZTX688B equivalent, key selection criteria include saturation voltage under high-current drive, thermal resistance (R_th(j-amb) = 116 °C/W on 1-in² PCB copper), gain linearity across 0.1–3 A, and TO-92 compatibility for legacy board reuse.

Technical Context

The ZTX688B operates as a medium-power NPN switch with DC current gain (h_FE) specified from 100 to 500 across I_C = 0.1–10 A, supporting robust Darlington pair configurations. Its f_T = 150 MHz enables fast switching (t_on = 40 ns, t_off = 500 ns) under pulsed 500 mA loads at V_CC = 10 V.

Thermal design is anchored by R_th(j-case) = 70 °C/W and R_th(j-amb) = 116 °C/W on standard PCB mounting, with safe operating area (SOA) validated up to T_j = +175 °C and transient pulse limits defined for duty cycles ≤2%.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	12 V - maximum collector-emitter voltage before breakdown; defines rail limit in 12 V motor driver stages
h_FE @ I_C=3 A	400 - stable DC current gain at high output current; ensures reliable base drive sizing for 3 A load switching
V_CE(sat) @ I_C=3 A	0.18 V - low saturation voltage reduces conduction loss to ≤0.54 W at full rated current
f_T	150 MHz - usable for PWM frequencies up to ~10 MHz with controlled rise/fall times
R_th(j-amb)	116 °C/W - thermal resistance on 1-in² PCB copper; enables 1.5 W continuous dissipation at T_amb = 25 °C
t_off	500 ns - turn-off delay under 500 mA load; supports >100 kHz switching in flash converter topologies

Pinout & Package

Package: TO-92 (E-Line compatible, 3-lead plastic). Mounting requires minimum 1-inch² copper area for rated power dissipation.

Pin/Terminal	Circuit Role	Design Meaning
E (Emitter)	Current sink terminal	Connected to ground or low-side return path; carries full load current with minimal voltage drop
B (Base)	Control input	Receives current-limited drive (e.g., 20 mA for 3 A I_C); requires series resistor to prevent overdrive
C (Collector)	High-side current source	Switches positive rail to load; must be routed with low-inductance trace for fast switching integrity

Key Features

Feature	Design Value
Low V_CE(sat) at high I_C	0.18 V @ 3 A - cuts conduction loss by >40% vs. standard general-purpose transistors
High h_FE linearity	500 @ 0.1 A → 400 @ 3 A → 100 @ 10 A - maintains predictable base drive across wide load range
Fast switching speed	t_on/t_off = 40/500 ns - enables efficient operation in 50–200 kHz DC-DC and flash charging circuits
Extended temperature range	T_j = –55 °C to +200 °C - supports operation in automotive under-hood and industrial motor control environments

Applications

Motor Driver Stage

Flash Gun Converter

Use Scenario: Driving 12 V brushed DC motors in portable tools with peak currents up to 3 A.

IC Role / Device Role / Timing Role: High-current NPN switch controlling motor direction and PWM speed via base-driven saturation.

Use Value: Low V_CE(sat) minimizes heat generation during sustained 2–3 A operation, eliminating need for heatsink on TO-92 package.

Use Scenario: Boosting capacitor charge voltage from 3 V battery to 300 V in camera flash circuits.

IC Role / Device Role / Timing Role: Primary switching transistor in flyback or Royer oscillator topology, gated at ~20–50 kHz.

Use Value: 150 MHz f_T and 40 ns t_on ensure clean square-wave drive to transformer primary, improving energy transfer efficiency.

Darlington Pair Input

Battery-Powered Load Switch

Use Scenario: Serving as the input stage of a complementary Darlington pair for high-current linear regulators.

IC Role / Device Role / Timing Role: First-stage amplifier providing high h_FE (500) to reduce required drive current for second-stage transistor.

Use Value: Gain stability across I_C = 0.1–1 A allows precise base current calculation without iterative compensation.

Use Scenario: Enabling/disabling 12 V subsystems (e.g., sensors, displays) in handheld medical devices.

IC Role / Device Role / Timing Role: Low-leakage (I_CBO = 0.1 µA) NPN switch isolating downstream circuitry from battery when off.

Use Value: Ultra-low cutoff current extends shelf life in battery-critical applications where standby drain must be <1 µA.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
ZTX653	V_CEO = 60 V, h_FE = 200 @ 3 A, higher V_CE(sat) (0.25 V)	Better suited for higher-voltage rails (>24 V); less efficient at 12 V due to higher saturation loss	Select if system requires >30 V breakdown margin and can tolerate 40% higher conduction loss
BCX56-10	h_FE = 100–250 @ 1 A, V_CE(sat) = 0.3 V @ 1 A, TO-92 but lower P_tot (0.8 W)	Limited to ≤1 A continuous; unsuitable for 3 A motor or flash load peaks	Only acceptable for signal-level or sub-500 mA switching where gain and speed are secondary

Compared with ZTX653 and BCX56-10, the ZTX688B uniquely balances 12 V rail compatibility, 3 A current capability, and sub-0.2 V saturation - making it the only TO-92 option qualified for sustained 1.5 W dissipation in compact battery-powered systems.

Availability

ZTX688B is available at Aetrix Electronics and suitable for motor drivers, flash gun converters, Darlington input stages, and battery-powered load switches requiring stable component supply and long-term industrial availability.

Supply support for ZTX688B 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 semiconductor company specializing in discrete, analog, and mixed-signal solutions for industrial, computing, consumer, and communications markets.

The ZTX688B belongs to Diodes' high-gain medium-power bipolar transistor product line, engineered specifically for space-constrained, thermally sensitive switching applications where TO-92 footprint and low V_CE(sat) are critical.

FAQ

What is the maximum continuous collector current for ZTX688B at 70°C ambient?

At T_amb = 70 °C, the ZTX688B's derated continuous collector current is 2.1 A. This is calculated using its 116 °C/W junction-to-ambient thermal resistance and 1.5 W practical power dissipation rating: (150 °C − 70 °C) / 116 °C/W = 0.69 W max; then I_C = √(P / R_CE(sat)) ≈ 2.1 A assuming typical V_CE(sat) ≈ 0.15 V.

Can ZTX688B replace a BC337 in a 12 V motor driver?

Yes - but only if the BC337 is used below 500 mA. The ZTX688B delivers 3× the current (3 A vs. 0.8 A), 4× the gain (400 vs. 100), and lower V_CE(sat) (0.18 V vs. 0.7 V), enabling direct upgrade without circuit redesign, provided PCB copper area meets 1-in² minimum for thermal performance.

Is ZTX688B suitable for linear regulator pass transistor use?

No - it is not optimized for linear operation. Its SOA curve shows limited safe area above 10 V V_CE, and its h_FE drops sharply above 3 A. Designed for saturated switching, not analog biasing; use complementary devices like ZTX951/ZTX952 for linear regulator pairs.

Does ZTX688B have lead-free and RoHS-compliant packaging?

Yes - Diodes Incorporated manufactures the ZTX688B in lead-free, RoHS-compliant TO-92 packages per their standard product release. The device meets JEDEC J-STD-020 moisture sensitivity level (MSL) 1 and is qualified for reflow soldering up to 260 °C peak temperature.

ZTX688B Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

Package/Case:: E-Line-3

Packaging:: Bulk

Product Status:: Discontinued at Digi-Key

Transistor Type:: NPN

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

Voltage - Collector Emitter Breakdown (Max):: 12 V

Vce Saturation (Max) @ Ib, Ic:: 350mV @ 20mA, 3A

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 500 @ 100mA, 2V

Power - Max:: 1 W

Frequency - Transition:: 150MHz

Operating Temperature:: -55°C ~ 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: E-Line (TO-92 compatible)

ZTX688B FAQ

1.How can I place an order for ZTX688B through Aetrix?

Please submit a Request for Quotation (RFQ) for ZTX688B 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 ZTX688B reliable?

The price and inventory of ZTX688B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZTX688B is usually 5 days.

3.What payment methods are accepted for ZTX688B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZTX688B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZTX688B?

ZTX688B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZTX688B 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 ZTX688B?

For technical support, including ZTX688B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZTX688B requirements.

6.How does Aetrix verify that ZTX688B is sourced from the original manufacturer or authorized distributors?

All ZTX688B 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 ZTX688B meets industry standards.

7.What is the process for return or replacement of ZTX688B?

All ZTX688B units undergo pre-shipment inspection (PSI). If there is an issue with ZTX688B, 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 ZTX688B part is unused and in its original packaging.

Return procedure for ZTX688B:

1.Submit a request within 90 days.

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

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