{"id":90786,"date":"2024-10-09T10:00:39","date_gmt":"2024-10-09T08:00:39","guid":{"rendered":"https:\/\/botland.com.pl\/blog\/2n3904-what-is-it-and-what-is-it-used-for\/"},"modified":"2026-04-08T10:48:17","modified_gmt":"2026-04-08T08:48:17","slug":"2n3904-what-is-it-and-what-is-it-used-for","status":"publish","type":"post","link":"https:\/\/botland.store\/blog\/2n3904-what-is-it-and-what-is-it-used-for\/","title":{"rendered":"2N3904 – What is it and what is it used for?"},"content":{"rendered":"Reading time:<\/span> 4<\/span> min.<\/span><\/span>\t\t
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The 2N3904 bipolar trans<\/strong> istor is one of the most popular and widely used NPN transistors.
\nIn this article, we will look at the technical characteristics of this element and its example applications in electronics! <\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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NPN transistor 2N3904 - characteristic parameters<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The 2N3904<\/a> is a bipolar transistor with an NPN<\/strong> conduction type – this means that current flows from the emitter to the collector when a suitable threshold voltage is applied to the base.
\nIt is a low-power transistor<\/a>, but has a relatively high current amplification factor (hFE), which usually ranges from tens to hundreds.
\nThe allowable collector-emitter voltage (Vceo) is about 40V, which means that the 2N3904 transistor can switch voltages of this level.
\nSimilarly, the allowable collector-base voltage (Vcb) is also about 40V.
\nIn contrast, the maximum emitter-base voltage (Veb) is about 6V.
\nThe 2N3904 transistor can conduct a continuous collector current (Ic) of up to 200mA.
\nThe base current (Ib) is proportional to the collector current and is determined by the current gain factor.
\nThe 2N3904 is available in various housings, such as TO-92 (THT mounting), SOT-23 (SMD mounting) and others. <\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Applications of the 2N3904 transistor in electronics<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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NPN 2N3904 bipolar transistor 40V\/0.2A - 5pcs.<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Although the 2N3904 transistor is a low-power signal component, its applications are wide<\/strong> and include.
\nlow-power amplifiers, electronic switches, detectors, voltage regulators, electronic protection, as well as noise generators.
\nWhen designing electronic circuits with transistors, it is important to become familiar with the exact parameters<\/strong> available in datasheets, including electrical parameters, current and voltage characteristics, and frequency characteristics.
\nThe 2N3904 transistor is often used because of its versatility, availability, low purchase cost and good electrical performance, making it a popular choice for many electronic applications. <\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t<\/section>\n\t\t\t\t

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Testing a bipolar transistor<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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To test an NPN-type bipolar transistor<\/a> with a multimeter, you can use the diode test mode of the multimeter.
\nTurn off the power to the circuit under test and make sure the transistor is disconnected from any live power circuit.
\nSet the multimeter<\/a> to diode test mode and identify the connectors of the transistor.
\nAn NPN transistor has three junctions: emitter (E), base
\n(B) and collector
\n(C).
\nThe multimeter used here so that it can measure the voltage at any two connectors of the transistor.
\nIn diode mode, the multimeter supplies the transistor with a small voltage and helps identify the diodes embedded in the transistor. <\/p>\n

We connect the red probe of the multimeter to the base (B) of the transistor.
\nHolding the black probe, check the connection between the base (B) and emitter (E).
\nThe voltage will drop on the ,,diode” base-emitter.
\nThen, holding the red probe on the base of the transistor, we apply the black probe to the collector.
\nAt the base-collector junction, the voltage drop should also be similar to that at the base-emitter junction, checked in an identical manner. <\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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Switching and control with 2N3904 transistor<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The NPN bipolar transistor, like the 2N3904, can be used in various circuits, including frequency filters<\/strong>.
\nIn a high-pass and low-pass filter, NPN 2N3904 transistors can be used as operational amplifiers<\/a> to provide appropriate signal gain in specific frequency bands.
\nThe 2N3904 can be used in an operational amplifier configuration to amplify the input signal before passing it through filter elements such as capacitors and inductors.
\nThe NPN transistor can be used as an amplifying element in a band-pass filter.
\nIn this case, the 2N3904 can be used as part of an amplifier configuration that amplifies the signal in the frequency band to be passed through the filter.
\nIn a low-pass filter with an active element, the NPN transistor can be used as part of a low-pass filter circuit in which the signal is passed through a capacitor and resistor.
\nThe 2N3904 can be used as an operational amplifier in an integrating (integrator) or differentiating configuration, which are often used in this type of filter.
\nIn low-pass filters with an inductor, the NPN transistor can be used as a signal amplification element before passing it through the inductor and capacitor.
\nThe 2N3904 can be used as part of an operational amplifier or in an emitter or collector common-circuit configuration to amplify the signal. <\/p>\n

All of these applications require appropriate circuit design<\/strong> based on the properties of the 2N3904 transistor and frequency filtering requirements.
\nThe NPN transistor can be used as an amplifier, a key or a regulating element in frequency filters depending on the needs of the project. <\/p>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t

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2N3906 - complementary pair for 2N3904<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The complementary pair for the 2N3904<\/a>, is the PNP transistor 2N3906<\/strong>.
\nThis means that they are PNP (2N3906) and NPN (2N3904) bipolar transistors, which have similar characteristics, but with opposite types of conductivity: <\/p>\n