The MPSA06 and complementary MPSA56 are ideal companions for audio amplifier input circuitry. With an 80 V_CE rating, 500 mA capacity, and a DC current gain of 100, they are also suitable for a variety of switching or driver applications. The MPSA06 family is a solid member of the jellybean semiconductor club, especially when we consider variants such as the SOT-23 and the more capable SOT-223 package as shown in Figure 1 for the OnSemi (Fairchild) MPSA06.
Figure 1: Datasheet for the OnSemi (Fairchild) MPSA06 transistor and variants.
History of the MPSA06 and MPSA56
Many jellybean components originated in the late 1960 and 1970. While I have yet to determine the specific launch year for the MPSA06 and the MPSA56, they were unceremoniously listed in Motorola’s 1983 edition of the Small-Signal Transistor Data handbook. This suggests that they were already well-established components.
The part number MPS prefix may be interpreted as “Motorola, Plastic, Small-signal transistor.” It’s interesting to note that Motorola would rebrand standard JEDEC parts such as the 2N3904 which was branded as the Motorola MPS3904. The “A” designation is uncertain, but likely refers to device packaging. For example, there were several closely related components including the MPSU06 (NPN) / MPSU56 (PNP) pair in a 1 W TO-202 package and the MPSW06 (NPN) / MPSW56 (PNP) pair in a 1W (extended length) TO-92 (TO-226AE) package.
Tech Tip: Parts such as the MPSU06 and MPSW06 are largely lost to history. Equipment can still be repaired using DigiKey transistors. For most applications (audio and switching), you will need to match or exceed parameters such as V_CE, gain, and power dissipation. You may also need to be creative with the soldering to make sure your transistor is properly installed on the PCB, as not all transistors have an E-B-C pinout.
Locating MPSA06 components in DigiKey
The DigiKey tools are designed to help you find a needle in a haystack. You could search directly for the MPSA06 or the MPSA56. You will quickly locate a few parts. However, that’s not the way to search for the jellybean parts. Instead, we should search using a root number and type keyword such as “A06 BJT” or “A56 BJT”. This will return all DigiKey components independent of the prefix and suffix that are often appended to the components.
The keyword search “A06 BJT” casts a wide net that occasionally catches a wayward components, However, it generally does a good job of locating the original TO-92 components and surface mount variants including the OnSemi PZTA06 as shown in Figure 2.
Figure 2: Image of an MPSA06 descendent in a SOT-223-4 package.
Parting thoughts
Searching DigiKey reveals that over a million variants of the original MPSA06 / MPSA56 are in stock. While not as popular as the 2N3904 family, the MPAS06 family has been a reliable friend for at least 40 years and will likely be with us for many decades to come.
Look for the MPSA06 family as the rail voltage starts to get higher. A perfect application is the low-power sections of an audio and guitar amplifier.
Best wishes,
APDahlen
Related Information
Please follow these links to related and useful information:
About this author
Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET-accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this.