MMBT4401 Bipolar Junction Transistor Diodes Incorporated MMBT4401 Bipolar Junction Transistor (BJT) with epitaxial planar die construction is a 40V NPN small signal transistor. The MMBT4401 is qualified to AEC-Q101 standards for high reliability, available in the SOT23 package. This transistor is constructed from molded plastic 'Green' compound and complies with UL94V-0 flammability rating. Diodes Incorporated MMBT4401 features a wide storage and operating temperature range of -55ºC to 150ºC. This BJT is RoHS compliant. The MMBT4401 transistor is ideal for medium power amplification and switching.