12/11/2023 0 Comments 2n 3904 datasheetMeasure the transistor’s cut-off frequency fβ and calculate its characteristic frequency fT using the “gain-bandwidth product” method. When the effective value of the voltage between the two terminals of R1 measured by the oscilloscope is 50 mVrms, and since R1 = 100 kohms, Ib is approximately equal to 0.5 uA. Set the signal source output to a 1 kHz sine wave and change the output amplitude. Calculate the effective value of Ib current so that Ib is approximately equal to 0.5 uA. Set the signal source output to a 1 kHz sine wave, adjust the signal source output signal amplitude, and use oscilloscope channel 2 to test the voltage waveform between the two terminals of R1 (connect the banana head interface marked as Input). The h-parameters of the transistor reflect the small-signal AC characteristics of the transistor under certain fixed static conditions.Ĭonnect the signal generator output to the BNC interface on the left side of the experimental board’s AC IN, and connect the oscilloscope Channel 1 to the BNC interface on the right side of the experimental board’s AC OUT. Where Ib and Vbe are the input variables of the transistor, and Ic and Vce are the output variables. With a reasonable setting of the static operating point and an AC small signal input, the transistor can be equivalent to a linear two-port circuit, represented by AC components of current and voltage. ![]() Once the base current separates, the transistor will turn off, so this phase is called the cutoff region, and the VBE may be around 600mV. Moreover, the collector-emitter/collector-base terminals are capable of handling typical voltages of 40V and 60V respectively. This particular stage is referred to as the saturation region. When the 2N3904 NPN transistor is completely biased, it permits a maximum of 200mA to flow through two specific terminals, namely emitter and collector. Once the current supply is given to the base terminal, the transistor can be biased. The maximum current supply across the collector terminal is 200mA, so loads consuming more than 200mA cannot be connected via this transistor. The high gain value of the 2N3904 transistor is 300, which determines its amplification ability. ![]() Similarly, once a signal is given to the base pin, it will be forward biased. Due to this biasing current, 2N3904 goes to the saturation state and the LED turns ON.If the base pin is connected to the GND terminal, both the emitter and collector terminals are reverse biased or left open. When the switch is closed, the base of the transistor is biased, and current flows to the base of the transistor. Due to this, 2N3904 remains in the cut-off state and the LED does not glow. ![]() And no current flows to the base of the transistor. When the switch is open, the base of the transistor is not biased. The required resistor value can be easily calculated using Ohm’s law. Proper biasing of the base ensures adequate base current to turn ON the transistor.Ī resistor of 220 Ohm is connected between the load(LED) and the collector terminal to protect the LED from overcurrent. The base of the transistor is biased using a 10 K Ohm resistor(R3) in parallel to the 1 K Ohm resistor(R2) plus base-emitter junction resistance(in series). The complete circuit is powered via a 5 V supply. In the circuit diagram given above, 2N3904 is used as a switch to turn ON/OFF an LED connected at the collector terminal.
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