Experiment A:1) Fundamental of basic electrical instrument Objectives: Operate basic electrical laboratory tools (oscilloscope, function generator, DC power supply). Determine transistor type (NPN, PnP), terminals, and material using digital multimeter. Graph the collector characteristics of a transistor using experimental methods and determine. Determine the value of the alpha and beta ratios of a transistor. Construct series and shunt voltages regulator configurations. Calculate and measure Vout when input power supply Vin is changed while resistor load Rl is fixed and vice versa for voltage regulator circuit. Describe the difference of clipping and climping circuits. Analyze inverting amplifier, non-inverting amplifier, summing amplifier and multistage of op-amp circuits.
Part 1A :Fundamental of basic electrical instrument.
Theory :The oscilloscope, often just called the scope, displays the signals as a plot of magnitude versus time. It is an electronic test instrument that displays electrical signals graphically, usually as a voltage (vertical or Y axis) versus time (horizontal or X axis) as shown in figure 1. The intensity or brightness of a waveform is sometimes considered the Z axis. There are some applications where other vertical axes such as current may be used, and other horizontal axes such as frequency or another voltage may be used.. A signal or function generator is used to produce periodic signals of the frequency, amplitude, and waveform needed for input to the device under test. The counter/timer can measure time intervals and frequencies very accurately, and the digital multimeter measure voltages, currents, resistance, and it can test silicon diodes and transistors. Everything you do in an electronics laboratory depends upon your familiarity with these instruments.
Procedures: First of all, all the switches of the oscilloscope was studied and a adjusted to various values. The function generator was adjusted to a 1000 Hz sinusoidal waveform. On the oscilloscope, the vertical sensitivity was set to 1V/div. Finally the amplitude control of the function generator was adjusted to a 4V peak-to-peak (p-p) sinusoidal waveform on the screen of the oscilloscope. Then the circuit in the below figure was constructed. The function generator was set to sin wave output and frequency to 100Hz. The probe and ground clip of the scope were connected to point A and C. Then the scope was turned on, and th AC-GND-DC was set to AC coupling. The amplitude control of function generator and the scope’s controls were adjusted to produce a single sin wave with 6Vp-p. VOLTS/DIV settings and the value were recorded in a table. Then TIME/DIV was adjusted until an appropriate size of signal is achieved. After this the data was recorded in a table. Finally, the same steps were done to measure the voltage across point B and C.
Results :VOLTS/DIV (V/div) output Voltage (V)P-P TIME/DIV(ms/div) Time division (ms) A to C 1 6 2 10.4 B to C 1 5.2 2 10.4
Discussion :As can be seen from the table above, the voltage between A and C is bigger than the voltage from B to C. This is a result of the bigger resistance between A to C, which was 5Kohm while the resistance between B an C was just 1Kohm. Accordingly as long as the resistance is increased the voltage will simultaneously will be increased.
Conclusion :To sum up this experiment, all the objectives were successfully approached, and students were able to deal the instruments correctly.
part 2A :Characteristics of BJT (Bipolar Junction Transistor)
Theory :A bipolar (junction) transistor (BJT) is a three-terminal electronic device constructed of doped semiconductor material and may be used in amplifying or switching applications. Transistor is an abbreviation to...
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