PXT3904 bipolar transistor — Specifications & Equivalents

About the PXT3904

The PXT3904 is an NPN bipolar transistor with a collector–emitter voltage (V_CEO) rating of 40 V, a continuous collector current (I_C) of 0.2 A and a DC current gain (h_FE) of minimum 100. It can dissipate up to 0.5 W and is rated to a junction temperature of 150 °C. It is supplied in the SOT89 package.

At a glance

• Type: NPN bipolar transistor
• Max collector–emitter voltage (V_CEO): 40 V
• Max collector current (I_C): 0.2 A
• DC current gain (h_FE): minimum 100
• Transition frequency (f_T): 300 MHz
• Power dissipation (P_D): 0.5 W
• Max junction temperature (T_J): 150 °C
• Package: SOT89

Typical applications

Judging from its ratings the PXT3904 is generally applied in RF and high-speed switching stages and small-signal amplification and general-purpose switching.

A transition frequency (f_T) of 300 MHz indicates the frequency range over which useful current gain remains available.

The quoted current gain of minimum 100 determines the base drive needed: divide your target collector current by the minimum h_FE, not the typical figure, when sizing the base resistor.

Biasing and absolute maximum ratings

Absolute-maximum breakdown limits are V_CEO 40 V, V_CBO 60 V and V_EBO 6 V (magnitudes). The emitter–base rating is the easiest to overlook and is often only a few volts, so protect the junction against reverse drive.

Dissipation is capped at 0.5 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the PXT3904

A drop-in substitute for the PXT3904 must be the same NPN type and offer a collector–emitter rating of at least 40 V, a collector current rating of at least 0.2 A, current gain in the same ballpark as minimum 100 and a transition frequency of at least 300 MHz for the same bandwidth.

Mechanically, check the replacement against the SOT89 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

Where the application switches inductive loads or runs near the voltage limit, keep extra headroom rather than choosing a part that only just meets the original numbers.

Frequently asked questions

What is the PXT3904?

The PXT3904 is an NPN bipolar junction transistor (BJT). It is rated for 40 V collector-emitter and 0.2 A continuous collector current.

What is the maximum voltage of the PXT3904?

Maximum collector-emitter voltage (Vceo) is 40 V, and collector-base (Vcbo) is 60 V.

How much current can the PXT3904 handle?

Continuous collector current is rated at 0.2 A, with dissipation limited to 0.5 W.

What is the hFE of the PXT3904?

DC current gain (hFE) is quoted as minimum 100. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the PXT3904 come in?

It is listed in SOT89. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the PXT3904?

This page lists 17 candidate equivalents matched on electrical ratings and package. Any replacement should meet or exceed the original voltage, current and dissipation figures and use a compatible drive level.