Diodes Incorporated ZTX788B

Overview

ZTX788B from Zetex Semiconductors (now Diodes Incorporated) is a PNP silicon planar medium-power high-gain bipolar junction transistor, designed for switching and linear amplification in low-voltage, medium-current applications. It features V_CEO = –15 V, h_FE = 300 at I_C = –2 A, V_CE(sat) = –0.25 V at I_C = –1 A / I_B = –5 mA, and f_T = 100 MHz - enabling use in flash gun converters and motor drivers where low saturation loss and robust gain are critical.

For engineers reviewing the ZTX788B datasheet, ZTX788B pinout, ZTX788B application, or ZTX788B equivalent, key selection considerations include its TO-92-compatible E-Line package, PNP polarity with –15 V breakdown ratings, high DC current gain across 10 mA–6 A, low V_BE(sat) of –0.9 V, and thermal resistance R_th(j-amb) = 175 °C/W on standard PCB mounting.

Technical Context

The ZTX788B operates as a medium-power PNP BJT optimized for saturated switching and analog amplification in battery-powered systems. Its design emphasizes high h_FE stability over wide I_C range (10 mA to 6 A), low V_CE(sat) down to –0.15 V, and fast switching (t_on = 35 ns, t_off = 400 ns) under pulsed conditions (300 µs, ≤2% duty cycle).

Thermal performance is defined for two mounting conditions: R_th(j-amb) = 175 °C/W (free-air) and 116 °C/W (1-inch² copper PCB), with R_th(j-case) = 70 °C/W. Safe operating area (SOA) curves confirm capability up to –3 A continuous and –8 A peak pulse, constrained by V_CEO = –15 V and T_j ≤ +200 °C.

Key Specifications

Pinout & Package

Package: TO-92-compatible E-Line (3-lead plastic case, JEDEC TO-92 outline), lead-forming option available per datasheet drawing 3-273. Mounting requires ≥1 inch² copper area for rated 1.5 W dissipation.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD2955 and BC557B, the ZTX788B uniquely balances TO-92 mountability, –15 V rating, 300+ h_FE at –2 A, and sub-0.3 V saturation - making it optimal for space-constrained, medium-current PNP switching where thermal and gain trade-offs must be tightly controlled.

Availability

ZTX788B is available at Aetrix Electronics and suitable for flash gun converters, battery-powered motor drivers, Darlington base stages, and low-voltage linear regulators requiring stable component supply and consistent parametric performance across production batches.

Supply support for ZTX788B 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

Zetex Semiconductors, acquired by Diodes Incorporated in 2008, specialized in high-performance discrete semiconductors for power management and signal conditioning in portable and industrial electronics.

The ZTX series was developed for medium-power bipolar switching applications demanding high gain, low saturation, and robust thermal behavior in compact through-hole packages - directly addressing design needs in battery-operated and thermally constrained systems.

FAQ

Is ZTX788B suitable for surface-mount assembly?

No - ZTX788B uses a through-hole TO-92-compatible E-Line package with axial leads. It is not designed for reflow soldering or pick-and-place automation. For SMT equivalents, consider Diodes Inc.'s DXT788BVQ (SOT-23) or DMG3415L (P-channel MOSFET alternative), though gain and saturation characteristics differ significantly.

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

At T_amb = 70°C, derating from 25°C gives ΔT = 45°C. With 5.7 mW/°C derating, allowable power loss drops by 256.5 mW. Starting from 1.5 W, max P_tot = 1.2435 W. Using V_CE(sat) ≈ –0.25 V, max continuous I_C ≈ 4.97 A - but absolute maximum rating limits I_C to –3 A. Therefore, –3 A is the safe continuous limit regardless of thermal calculation.

Can ZTX788B replace a 2N3906 in high-current circuits?

No - while both are PNP BJTs, the 2N3906 is rated for only –200 mA continuous and –1 W dissipation. ZTX788B supports –3 A and 1.5 W, but its higher gain and different SOA require updated base drive design. Direct substitution without recalculating R_B and verifying thermal margin will cause overheating or premature failure.

Does ZTX788B have built-in ESD protection?

No - the datasheet does not specify ESD protection diodes or human-body-model (HBM) ratings. It is a bare-die planar transistor with no integrated clamping. External protection (e.g., series base resistor + parallel Zener) is recommended in environments with >2 kV HBM risk, especially during board handling or in motor-drive feedback paths.