Looking at the other specs the max collector to emitter voltage is 30V, transition frequency is 250MHz, minimum and maximum DC current gain is 30 to 300 and max collector dissipation is 625 Milliwatt.Īs mentioned it can be used for general purpose switching and amplification purposes. The maximum collector current of the transistor is 600mA, which is quite unique because mostly available TO-92 package transistors have 100mA to 200mA max collector current capability. The transistor is packed with quite good specs in its TO-92 package and low cost which makes it a reliable choice for wide variety of commercial and educational uses. It is a general purpose transistor and can be used in wide variety of switching and amplification applications. PN2222 is a popular transistor NPN bipolar junction transistor (BJT) available in TO-92 package. PN2222 Transistor Explained / Description: Max Storage, Operating & Junction temperature range: -55 to 150 Centigrade.Minimum & Maximum DC Current Gain (hFE): 30 to 300.Max Collector Dissipation (Pc): 625 Milliwatt.Max Collector-Emitter Voltage (VCE): 30V.Usually found in devices such as screamers, PA Systems & loudspeakers.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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