Authentic Supplies for the Transistor Historian and Kit Builder.


Available Only from the TransistorMuseum


All Transistors Tested

Before Shipment.



Historical Background


After the invention of the transistor in the late 1940s, there was rapid development of new device types and structures over the next two decades.  One important goal was to produce transistors capable of high frequency operation.  Philco was an early manufacturer of transistors, starting in 1953/54, with the famous Surface Barrier Type (SBT).  This used a unique electrochemical etching process during manufacture that allowed for an extremely thin germanium base layer, which in turn allowed the transistor to operate at very high frequencies (20 to 30 MHZ).  Philco sold millions of these transistors in the 1950s, which were used in high speed digital computer circuits and high frequency radio circuits.  Improvements to the SBT technology lead to even higher performing MAT and MADT transistors.   This latter type, Micro Alloy Diffused Base Transistor, was introduced by Philco in the late 1950s, and established the 2N501 as the “workhorse” of high speed digital and switching applications.  Several other transistor companies responded to this sales success with second source versions of the 2N501, including Sprague, General Transistor, General Instrument, CBS and ETCO. 






Your MADT Transistor Order Will be Supplied in the Storage/Display Envelope Shown Above, which Includes an Insert with Historical Description and a Schematic.





Germanium PNP MADT
Micro Alloy Diffused Base
Transistor Type 2N501

Vintage 1950s - 60s

Use: Computer



Your TransistorMuseum™

Order Will Contain:


Two Tested 2N501 Germanium PNP

 MADT High-Freq Transistors

(See the Style Shown Above)


Hobbyist Insert Depicting the Historical Importance of this Classic Transistor, Includes a Schematic of an Early Transistor Digital Logic Circuit Using the 2N501 MADT  Transistor


A TransistorMuseum™ Classic

Semiconductor Storage

 and Display Envelope 








$10 per Package (Two Transistors)

Includes Shipping Within U.S.


Email me at

To Determine Payments Options

(Paypal or Check)










By Jack Ward

All Rights Reserved.