The electrical characteristics of 2N2222 are summarized in a single table below. According to the datasheet, some of them have an operating crystal temperature (TJ) of up to +200 oC. New devices are manufactured using lead-free technology (Lead Free) and comply with the European RoHS standard.
Total Power Dissipation Ptot at T amb £ 25 ☌ 0.5 W.Emitter-base Voltage VEBO (I C = 0) 5 V.Collector-emitter VCEO Voltage (I B = 0) 30 V.Collector-base Voltage VCBO (I E = 0) 60 V.The maximum technical specifications of 2N2222 (at TA < +25oC): The datasheet states that the device is designed to operate at high switching speeds and provide effective amplification over a wide frequency range. They are true at ambient temperature (TA) of no more than +25oC. Let’s take a closer look at the 2N2222 transistor, its specifications and features. You should note that the “K” pin is physically connected to the metal case.
The pin assignment is as follows (clockwise from the small protrusion): Usually found in devices such as screamers, PA Systems & loudspeakers.The pinout of the 2N2222 in the TO-18 is shown in the figure below.Usage in Emergency services such as police & ambulance sirens.Civil defense uses such as alarms for early warning systems.Industrial uses such as fire & substance danger alarms.Commonly used in home security setups & monitoring systems.The tone signal from the speaker will be an increasing or decreasing tone depending on whether the circuit is switched on or off. On disconnecting the circuit from the power, the capacitor C1 discharges slowly resulting in a decreasing frequency cycle. This increasing voltage results in a decreasing time constant at the R2/C2 junction, Which also results in an increased frequency of the multivibrator.
When the circuit is switched on, the capacitor C1 charges slowly till it reaches its maximum voltage level. Combined, the two transistors represent a self-triggering multivibrator. This is due to the generator part of the circuit, which is a combination of PNP (2N2907) and NPN (2N2222) transistors. This circuit produces a sound very similar to a siren.
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