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Transistor Current Amplification

Transistor Current Amplification
Бакытгуль Абыканова, заведующий кафедрой, кандидат педагогических наук, доцент

Гулдана Бекова, старший преподаватель

Атырауский государственный университет имени Х. Досмухамедова, Казахстан

Участник конференции

 

Keywords:Transistor, Amplification, Electricity

 

In nature there are no two identical elements, i.e., all the real elements have a large spread of values, which leads to errors during the experiment.  Electronics Workbench in all of the elements described are strictly defined parameters, so every time the experiment is repeated a result, only parameters defined by the elements and the calculation algorithm.

Ease of measurement: Studying is impossible without errors, and errors in a real lab can sometimes be very costly to the experimenter. Working with Electronics Workbench, the experimenter is insured against accidental electric shock and equipment will not go down because of an incorrectly assembled circuit.  Through this program the user has available a wide range of devices, which are unlikely to be available in real life.

Thus, you always have a unique opportunity to plan and conduct a wide range of studies of electronic circuits in minimal time. Sophisticated graphics capabilities of the scheme take a lot of space, the image at the same time trying to make it more dense, which often leads to errors in connecting the wires to the elements of the chain.The library of the program has the components: passive components, transistors, controlled sources, managed switches, hybrid elements, indicators, logic elements, trigger devices, digital and analog components, special combinational and sequential circuits.


Active elements can be represented as a perfect model of the real elements.You can also create your own models of the elements and add them to the library elements. The program uses a large set of instruments for measurement: ammeter, voltmeter, oscilloscope, multimeter, Bode plotter (plotting frequency characteristics of the circuits), and function generator, the generator of the words, logic analyzer and a logic inverter.

Working with Electronics Workbench

The program Electronics Workbench is designed for modeling and analysis of electronic circuits. Features of the program Electronics Workbench v.5 roughly equivalent to the capacity of the program Microcap and allow you to work from basic experiments to experiments on statistical modeling.

1. Objective

  • The construction of the load line of the transistor stage.
  • Setting the operating point of the transistor stage.
  • Investigation of the parameters of the working point of the transistor.
  • Investigation of conditions for the transfer of the transistor in the saturation regime and cutoff.
  • Determination of the static transfer coefficient of the transistor cascade from the experimental data.
  • Determination of voltage gain of the transistor cascade from the experimental data.
  • Determination of current gain of the transistor cascade from the experimental data.
  • Defining the gain of the power transistor stage.
  • Determination of the input impedance of the transistor stage.
  • Determining output resistance of the transistor stage.
  • Definition of operation modes of the transistor, in which there are distortions of the output amplifier.

2. Equipment at your workingplace

  • · Laboratory Facility PU-2000.
  • · Removable motherboard EB-111.
  • · Connecting cables and jumpers.
  • · Multimeter.
  • · Dual beam oscilloscope.
  • · Computer.

3. Bried details of theory

The properties of the amplifier is determined by the choice of operating point DC. Mode, which employs amplification stage, can be determined by constructing a line to load on the output characteristics of the transistor.

One of the most common practical ways to set the operating point of the transistor in the amplifier stage is to use a voltage divider (Fig. 1).

Fig. 1

The collector current in the amplifying mode is described by the load line:

The operating point is determined by the intersection of the load line and the output characteristics of the transistor. Engine air flow for known values of R1 and R2, the transistor base current is given by:

For a symmetrical AC output amplifier collector voltageVCEshould be approximately equal to half the voltage of the collector circuit.

The voltage gain of the amplifier stage is determined by the ratio of the amplitudes of the output signal to the input:

                                                                                                               (10)

The input resistance of the amplifier of AC is defined as the ratio of the amplitudes of the input voltage and input current:

                                                                                                                    (11)

The value of the differential output resistance of the amplifier is a voltage Uххidle at the amplifier output, which can be measured as a voltage drop across the load resistance, greater than 200 kOhm, and voltage Uout, measured for a given load resistance RL, the following equation is solved forRout:

The saturation regimeis characterized by a low dropout voltage UCE. In the cut-off the collector current is zero and does not create the resistor voltage drop across RCConsequently, the voltage  UCEin cutoff mode and is equal to the maximum supply voltage.

4. The procedure of the experiment

Investigation of the Electronics Workbench simulation

EWb-1. Setting the operating point of the transistor.

1. Assemble a circuit for setting the operating point of transistor dc with a voltage divider (Fig. 4).

Fig. 2

2. Turn on the circuit and record the results of measurements in Table 5.7. Calculate the current transfer ratio?.

3. Calculate the voltage at the base of transistor UB, obtained using a voltage divider. Based on this value and taking into account thatUBE0= 0.7 V, calculate the emitter current and the ratio between the currents of the transistor, calculate the collector current. The calculated values of the emitter and collector currents, calculate the voltage between the collector and emitter of  UCE. The results of calculations write to the table. Compare the measured and calculated values.

4. Conduct a change in the resistance R1, to put the transistor in saturation and cutoff. Record test results in Table 6.

Table 1

Mode

R1, [kOhm]

UB, [V]

UCE, [V]

IB, [?A]

IC, [mA]

IE, [mA]

?

Active

 

 

 

 

 

 

 

Actual Calcualation

 

 

 

 

 

 

 

Saturation

 

 

 

 

 

 

 

Sections

 

 

 

 

 

 

 

EWb-2. Increasing alternating current signal

1. Assemble circuit in Figure 5.5 and turn it into work. Sketch the form of input and output signals.

Fig. 3

2. Determine the amplitude of the input and output signals and the results obtained, calculate the gain of the amplifier voltage. Write the result in Table 7.

Table 2

RL

Uin, [V]

Uout, [V]

KV

Rout

200[kOhm]

 

 

 

 

2 [kOhm]

 

 

 

3. Change the load (RL= 2 kOhm) and the results of measurements of the amplitudes of input and output, calculate the new value of the gain of the amplifier voltage.

4. Using the results of measurements of the amplitude of the output for two values of loads, calculate the output resistance of the amplifier.

5. By changing the resistance of resistor R1 2-3 times in one and the other side, sketch the received waveform. Explain the results.

6. Disconnect the capacitor C3 and sketch received waveform and explain changes in the output that occurred.

 

References:

  1. VI Karlaschuk. Electronic lab at the IBM PC. M., "SOLON-R," 2001.
  2. Electrical and electronics experiments and exercises: Workshop on Electronics Workbench: In 2 volumes / under total edited D.I.Panfilova. M. DODEKA, 2000.
  3. IS Potemkin Functional units of digital automation. - Moscow: Energoatomizdat, 1988. - 320.
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