2002. 9. 12 1/4 semiconductor technical data 2n3904 epitaxial planar npn transistor revision no : 1 general purpose application. switching application.
At 20mA, that's about 120 Ohms. The current gain depends on the collector current, but figure on 50. With a base current of 20mA, that's a collector current of way more than the 2N3904 can handle, so 20mA will saturate it thoroughly. You can probably get by with a lower base current. Look at a 2N3904 datasheet for gain at different collector ...
2N3904 Datasheet, 2N3904 PDF, 2N3904 Data sheet, 2N3904 manual, 2N3904 pdf, 2N3904, datenblatt, Electronics 2N3904, alldatasheet, free, datasheet, Datasheets, data ... Parallax Inc. 599 Menlo Drive, Ste.100, Rocklin, CA 95765 USA toll-free 888-512-1024 It is a little more powerful than the 2n3904. Most likely the current gain is less, and and maybe also the maximal voltages. Depending on your application that may be OK, which is quite likely if it is not too demanding. The correct thing would for you to check the numbers in the data sheet. 2n3904 [Old version datasheet] Medium Integrated Power Solution Using a Dual DC/DC Converter and an LDO [Old version datasheet] High-Integration, High-Efficiency Power Solution Using DC/DC Converters With DVFS
Order today, ships today. 2N3904TF – Bipolar (BJT) Transistor NPN 40V 200mA 300MHz 625mW Through Hole TO-92-3 from ON Semiconductor. Pricing and Availability on millions of electronic components from Digi-Key Electronics. 2N3904 General Purpose Transistors NPN TO-92 Page 1 31/05/05 V1.0 High Speed Switching Features: • NPN Silicon Planar Switching Transistors. • Fast switching devices exhibiting short turn-off and low saturation voltage characteristics. 2002. 9. 12 1/4 semiconductor technical data 2n3904 epitaxial planar npn transistor revision no : 1 general purpose application. switching application. Data sheet status Objective speciﬁcation This data sheet contains target or goal speciﬁcations for product development. Preliminary speciﬁcation This data sheet contains preliminary data; supplementary data may be published later.