MMBTA44 bipolar transistor — Specifications & Equivalents

About the MMBTA44

The MMBTA44 is an NPN bipolar transistor with a collector–emitter voltage (V_CEO) rating of 400 V, a continuous collector current (I_C) of 0.1 A and a DC current gain (h_FE) of minimum 50. It can dissipate up to 0.35 W and is rated to a junction temperature of 150 °C. It is supplied in the SOT23 package.

At a glance

• Type: NPN bipolar transistor
• Max collector–emitter voltage (V_CEO): 400 V
• Max collector current (I_C): 0.1 A
• DC current gain (h_FE): minimum 50
• Power dissipation (P_D): 0.35 W
• Max junction temperature (T_J): 150 °C
• Package: SOT23

Typical applications

Judging from its ratings the MMBTA44 is generally applied in small-signal amplification and general-purpose switching and high-voltage switching such as offline converters and lamp drivers.

The quoted current gain of minimum 50 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 400 V, V_CBO 500 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 0.35 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the MMBTA44

A drop-in substitute for the MMBTA44 must be the same NPN type and offer a collector–emitter rating of at least 400 V, a collector current rating of at least 0.1 A and current gain in the same ballpark as minimum 50.

Mechanically, check the replacement against the SOT23 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 MMBTA44?

The MMBTA44 is an NPN bipolar junction transistor (BJT). It is rated for 400 V collector-emitter and 0.1 A continuous collector current.

What is the maximum voltage of the MMBTA44?

Maximum collector-emitter voltage (Vceo) is 400 V, and collector-base (Vcbo) is 500 V.

How much current can the MMBTA44 handle?

Continuous collector current is rated at 0.1 A, with dissipation limited to 0.35 W.

What is the hFE of the MMBTA44?

DC current gain (hFE) is quoted as minimum 50. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the MMBTA44 come in?

It is listed in SOT23. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the MMBTA44?

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.