2SD1045 bipolar transistor — Specifications & Equivalents

About the 2SD1045

The 2SD1045 is an NPN bipolar transistor with a continuous collector current (I_C) of 3 A and a DC current gain (h_FE) of minimum 160. It can dissipate up to 0.9 W and is rated to a junction temperature of 150 °C. It is supplied in the TO92 package.

At a glance

• Type: NPN bipolar transistor
• Max collector current (I_C): 3 A
• DC current gain (h_FE): minimum 160
• Transition frequency (f_T): 100 MHz
• Power dissipation (P_D): 0.9 W
• Max junction temperature (T_J): 150 °C
• Package: TO92
• Manufacturer: Multi-source (JIS registered part number)

Typical applications

Judging from its ratings the 2SD1045 is generally applied in RF and high-speed switching stages.

A transition frequency (f_T) of 100 MHz indicates the frequency range over which useful current gain remains available.

The quoted current gain of minimum 160 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_CBO 30 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 0.9 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the 2SD1045

A drop-in substitute for the 2SD1045 must be the same NPN type and offer a collector current rating of at least 3 A, current gain in the same ballpark as minimum 160 and a transition frequency of at least 100 MHz for the same bandwidth.

Mechanically, check the replacement against the TO92 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

Because 2SD1045 is a JIS-registered part number rather than one vendor's proprietary series, it is produced by several manufacturers. Datasheet figures vary slightly between them, so check the datasheet of the brand you actually buy — this also makes like-for-like sourcing easier.

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 2SD1045?

The 2SD1045 is an NPN bipolar junction transistor (BJT).

How much current can the 2SD1045 handle?

Continuous collector current is rated at 3 A, with dissipation limited to 0.9 W.

What is the hFE of the 2SD1045?

DC current gain (hFE) is quoted as minimum 160. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the 2SD1045 come in?

It is listed in TO92. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the 2SD1045?

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.