TIP42 bipolar transistor — Specifications & Equivalents

About the TIP42

The TIP42 is a PNP bipolar transistor with a collector–emitter voltage (V_CEO) rating of 40 V, a continuous collector current (I_C) of 6 A and a DC current gain (h_FE) of minimum 20. It can dissipate up to 65 W and is rated to a junction temperature of 150 °C. It is supplied in the TO220 package.

At a glance

• Type: PNP bipolar transistor
• Max collector–emitter voltage (V_CEO): 40 V
• Max collector current (I_C): 6 A
• DC current gain (h_FE): minimum 20
• Transition frequency (f_T): 3 MHz
• Power dissipation (P_D): 65 W
• Max junction temperature (T_J): 150 °C
• Package: TO220
• Manufacturer: Multi-source (originally a Texas Instruments TIP series)

Typical applications

Judging from its ratings the TIP42 is generally applied in power output and driver stages.

A transition frequency (f_T) of 3 MHz indicates the frequency range over which useful current gain remains available.

The quoted current gain of minimum 20 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 80 V and V_EBO 5 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 65 W, and that figure assumes the datasheet's mounting and ambient conditions — derate it for your own thermal design.

Choosing a replacement for the TIP42

A drop-in substitute for the TIP42 must be the same PNP type and offer a collector–emitter rating of at least 40 V, a collector current rating of at least 6 A, current gain in the same ballpark as minimum 20 and a transition frequency of at least 3 MHz for the same bandwidth.

Mechanically, check the replacement against the TO220 footprint and confirm the pin order — parts sharing a package outline do not always share a pinout.

This is a widely second-sourced series, so verify parameters against the datasheet of the brand you are buying rather than assuming every version is identical.

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 TIP42?

The TIP42 is a PNP bipolar junction transistor (BJT). It is rated for 40 V collector-emitter and 6 A continuous collector current.

What is the maximum voltage of the TIP42?

Maximum collector-emitter voltage (Vceo) is 40 V, and collector-base (Vcbo) is 80 V.

How much current can the TIP42 handle?

Continuous collector current is rated at 6 A, with dissipation limited to 65 W.

What is the hFE of the TIP42?

DC current gain (hFE) is quoted as minimum 20. Size base drive from the minimum value so the transistor saturates fully across production spread.

What package does the TIP42 come in?

It is listed in TO220. Verify the pinout of the specific variant, as one outline can carry different pin assignments.

What can I use to replace the TIP42?

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.