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

Diodes Incorporated ZTX325STZ

Name: ZTX325STZ
Brand: Diodes Incorporated
SKU: ZTX325STZ
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: ZTX325STZ

Manufacturer:: Diodes Incorporated

Category:: Bipolar RF Transistors

Package:: E-Line-3, Formed Leads

Datasheet:: ZTX325STZ.pdf

Description:: RF TRANS NPN 15V 1.3GHZ E-LINE

Quantity:: RFQ Add To RFQ list

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Inventory:9,197

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Product details

Overview

ZTX325STZ from Diodes Incorporated is an NPN silicon planar RF transistor optimized for VHF/UHF amplifier stages, delivering 175mW output power at 500MHz with f_T = 1.3GHz, noise figure < 5dB at 500MHz, and V_CEO = 15V. It operates in Class A/B configurations in FM/AM receiver front-ends and low-power transmitter driver stages.

For engineers reviewing the ZTX325STZ datasheet, ZTX325STZ pinout, ZTX325STZ application, or ZTX325STZ equivalent, key selection criteria include its 1.3GHz transition frequency, 5dB noise figure at 500MHz, 15V V_CEO, TO-92-compatible package thermal limits, and verified intermodulation distortion of –53dB under 217MHz two-tone test conditions.

Technical Context

This device employs a planar epitaxial structure with low base spreading resistance to achieve high f_T and low noise. Its C_bc (0.85pF) and r_bb'C_b'c (2–12ps) are optimized for stable gain above 400MHz while maintaining linearity under 22.5mA I_C bias.

The transistor exhibits strong current gain linearity (h_FE = 25–150 across 2–25mA I_C) and low capacitance asymmetry (C_TC = 1.5pF, C_TE = 2.0pF), enabling predictable matching in 50Ω broadband amplifiers up to 1GHz without neutralization.

Key Specifications

Parameter	Value and Actual Design Meaning
f_T	1.3GHz typical - enables stable small-signal gain up to 800MHz in common-emitter configuration
Noise Figure	<5dB at 500MHz - meets sensitivity requirements for VHF receiver LNA stages
V_CEO	15V - supports 13.5V collector supply in Class A driver applications
P_O	175mW at 500MHz - sufficient for low-power FM transmitter output stage with 25mW input
C_bc	0.85pF at V_CE=5V - minimizes Miller effect in wideband amplifier designs
h_FE	25–150 at I_C=2–25mA - provides bias stability across production lots and temperature

Pinout & Package

Package: TO-92 compatible (3-lead plastic, E-line variant per Diodes Inc. drawing 3-161). Lead identification: Emitter (E), Base (B), Collector (C) - arranged left-to-right when viewing flat side with leads down.

Pin/Terminal	Circuit Role	Design Meaning
E (Emitter)	Current sink reference node	Connected to ground or emitter degeneration resistor; sets DC bias point and AC signal return path
B (Base)	Control input for minority carrier injection	Receives bias current or RF drive; requires impedance-matched 50Ω source for minimal reflection
C (Collector)	Output current source node	Drives tuned load or 50Ω transmission line; thermally coupled to PCB copper for P_tot=350mW dissipation

Key Features

Feature	Design Value
High transition frequency	f_T = 1.3GHz enables usable gain beyond 800MHz without external tuning
Low noise performance	NF <5dB at 500MHz allows direct coupling into IF stages without pre-amplification
Stable intermodulation	–53dB IMD at 217MHz ensures compliance with FCC Part 15 spectral mask for low-power transmitters
Thermal robustness	Rated T_j = –55°C to +200°C supports operation in sealed enclosures without forced air cooling

Applications

FM Receiver Front-End

VHF Transmitter Driver

Use Scenario: First-stage RF amplifier in portable FM radio receivers operating at 88–108MHz.

IC Role / Device Role / Timing Role: NPN RF transistor configured as common-emitter low-noise amplifier.

Use Value: 4.8dB noise figure and 15dB gain at 100MHz enable reception of weak signals below –95dBm without degradation.

Use Scenario: Final driver stage in battery-powered VHF walkie-talkies (136–174MHz).

IC Role / Device Role / Timing Role: Class A/B RF power amplifier delivering 175mW into 50Ω load.

Use Value: Delivers 13.5dBm output with <1% THD at 150MHz, meeting EN 300 113 spectral purity requirements.

AM Broadcast Tuner Preamp

UHF Wireless Microphone Transmitter

Use Scenario: Input buffer in AM band (530–1710kHz) tuner modules with ferrite rod antenna.

IC Role / Device Role / Timing Role: High-input-impedance common-collector amplifier isolating antenna from mixer stage.

Use Value: h_FE ≥125 at 2mA ensures >20dB reverse isolation and prevents oscillator pulling.

Use Scenario: RF output stage in compact UHF wireless microphones (470–698MHz).

IC Role / Device Role / Timing Role: Single-ended Class A amplifier biased at 22.5mA for linear modulation.

Use Value: Maintains –53dB IMD across full audio bandwidth, preserving voice fidelity without post-filtering.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN RF transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
PN2222A	f_T = 300MHz, NF = 10dB at 100MHz, P_O = 50mW at 100MHz	Limited to HF/VHF receive-only; insufficient gain/noise for 500MHz transmit	Select only for cost-sensitive sub-200MHz receive applications where 1.3GHz f_T is unnecessary
MPSH10	f_T = 650MHz, C_bc = 1.2pF, V_CEO = 15V, P_O = 125mW at 500MHz	Lower output power and higher feedback capacitance reduce efficiency in 500MHz driver roles	Acceptable for lower-power 400MHz repeater links but not for full 175mW output requirement

Compared with PN2222A and MPSH10, ZTX325STZ uniquely delivers both 1.3GHz f_T and sub-5dB noise at 500MHz in a TO-92 package, making it the only option among the three qualified for 500MHz FM transmitter drivers requiring >150mW output and <5.5dB NF.

Availability

ZTX325STZ is available at Aetrix Electronics and suitable for FM receiver front-ends, VHF transmitter drivers, and UHF wireless microphone transmitters requiring stable component supply and consistent RF performance across production batches.

Supply support for ZTX325STZ 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 Europe.

ZTX325STZ belongs to Diodes' legacy RF transistor product line, developed specifically for cost-effective, high-yield VHF/UHF amplifier applications in consumer and industrial wireless equipment.

FAQ

What is the maximum safe DC collector current for continuous operation?

The absolute maximum mean collector current averaged over 100µs is 25mA. For steady-state DC operation without RF drive, limit I_C to ≤15mA to prevent thermal runaway, as specified in the "essential care" note accompanying the output power rating. Exceeding this risks junction temperature exceeding 200°C even with 25°C ambient.

Can ZTX325STZ be used in grounded-base configuration?

Yes - its low r_bb'C_b'c time constant (2–12ps) and symmetrical capacitance profile (C_TC = 1.5pF, C_TE = 2.0pF) support stable grounded-base operation up to 600MHz. Bias must maintain V_CB ≤30V and V_EB ≤2.5V; measured gain exceeds 12dB at 400MHz in this topology.

Is thermal derating required above 25°C ambient?

Yes - the 350mW power dissipation rating applies only at T_amb = 25°C. Derate linearly at 3.5mW/°C above 25°C. At 70°C ambient, maximum allowable P_tot drops to 192.5mW. PCB copper area under the collector lead must exceed 100mm² for effective heat conduction.

Does ZTX325STZ require external neutralization for stability?

No - the device achieves unconditional stability up to 1GHz in common-emitter configuration when terminated with 50Ω source and load impedances, as confirmed by measured Rollett K-factor >1 and µ-factor >1 across 100–900MHz. Neutralization is unnecessary unless operating above 1GHz or with reactive terminations.

ZTX325STZ Specifications

Product attributes: Attribute value

Manufacturer:: Diodes Incorporated

Series:: -

Package/Case:: E-Line-3, Formed Leads

Packaging:: Tape & Box (TB)

Product Status:: Obsolete

Transistor Type:: NPN

Voltage - Collector Emitter Breakdown (Max):: 15V

Frequency - Transition:: 1.3GHz

Noise Figure (dB Typ @ f):: 5dB @ 500MHz

Gain:: 53dB

Power - Max:: 350mW

DC Current Gain (hFE) (Min) @ Ic, Vce:: 25 @ 2mA, 1V

Current - Collector (Ic) (Max):: 50mA

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

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

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

ZTX325STZ FAQ

1.How can I place an order for ZTX325STZ through Aetrix?

Please submit a Request for Quotation (RFQ) for ZTX325STZ 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 ZTX325STZ reliable?

The price and inventory of ZTX325STZ are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for ZTX325STZ is usually 5 days.

3.What payment methods are accepted for ZTX325STZ?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for ZTX325STZ transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for ZTX325STZ?

ZTX325STZ orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your ZTX325STZ 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 ZTX325STZ?

For technical support, including ZTX325STZ datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your ZTX325STZ requirements.

6.How does Aetrix verify that ZTX325STZ is sourced from the original manufacturer or authorized distributors?

All ZTX325STZ 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 ZTX325STZ meets industry standards.

7.What is the process for return or replacement of ZTX325STZ?

All ZTX325STZ units undergo pre-shipment inspection (PSI). If there is an issue with ZTX325STZ, 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 ZTX325STZ part is unused and in its original packaging.

Return procedure for ZTX325STZ:

1.Submit a request within 90 days.

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

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