﻿ Work tasks - Basic characteristics of the bipolar transistor
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## Basic features of the bipolar transistor

### Work Tasks and Measurement Procedures

##### Transfer (Current) Characteristic
1. Measure the point-by-point dependence of the collector current IC on the size-base current IB at a constant voltage between the collector and emitter UCE.

2. Plot the curve obtained from theory and compare qualitatively.

3. Determine the guideline that corresponds to the current gain factor β transistor in common emitter configuration by fitting a linear regression (e.g., in a spreadsheet) over the linear portion of the dependence.

##### Output (Collector) Characteristic
1. Measure the point-by-point dependence of the collector current IC on the voltage between the collector and emitter UCE for different values of the base current IB (e.g.  IB = 0 mA; 0,5 mA; 1 mA; … 2,5 mA).

2. Plot the resulting curves on a common graph and qualitatively compare the curves obtained with the dependence theories.

3. Compare the magnitude of the base current IB and the collector current IC at saturation of the transistor. Compare the values of the ratios with the current gain factor β.

#### Measurement procedure:

1. We perform a remote experiment Basic characteristics of the bipolar transistor.

##### Transfer (Current) Characteristic
1. We select the transfer characteristic measurement on the control panel of the remote task.

2. We set the voltage between the collector and the emitter UCE to about 3 V using the slider for the collector circuit.

3. Slightly increase the base current IB using the base circuit slider. Observe the voltage between the collector and emitter UCE. We adjust its value using the slider for the collector circuit if UCE changes significantly from the initially set value.

4. We save the experimental values in the table after the current stabilization of the base IB and collector IC (respecting the conditions of constant voltage between the collector and emitter UCE).

5. We change the value of the base current IB and repeat the measurement (see paragraphs 4 and 5) after saving the experimental data in the table.

6. The experimental values can be immediately plotted on a graph (Show graph button). This option can be used to continuously check the shape of the measured dependence. If the transfer characteristic is a linear dependence, the direction of this dependence corresponds to the current gain factor for a circuit with a common emitter.

7. We save the experimental data to the disk of the PC and stop the remote task after measuring the required data.

8. We open the resulting file in a spreadsheet program (MS Excel, Oo Calc, Kingsoft Spreadsheets…).

9. We plot to the graph an dependence of the collector current IC on the base current IB in the spreadsheet.

10. We interlace the obtained dependence in a spreadsheet by using linear regression (y = a.x + b) with displayed regression coefficients.

11. The value of the linear coefficient a in the regression equation is (see the expression (1)) is finding the value of the current gain factor β.

12. We compare the obtained value of the current gain factor β with the value of the coefficient h21 specified in the data sheet of the 2N3055 transistor.

##### Output (Collector) Characteristic
1. We select the output characteristic measurement on the control panel of the remote task.

2. We set a fixed value of the base current IB using the slider for the base circuit. We start with the value IB = 0 mA, then we will gradually set other values, e.g. 0.5 mA; 1 mA; … 2.5 mA, in other series of measurements.

3. Now we begin to gradually adjust the voltage between the collector and emitter UCE using the slider for the collector circuit. As a result, the collector current IC will change (it also depends on the chosen value of the base current IB). We check that the value of the base current IB does not change! If so, we adjust the value of its size using a slider base circuit.

4. After the stabilization of the measured variables IB, IC and UCE, we set the experimental values in the table (a separate table is always available for the measurement of the conversion and output characteristics, and it is possible to switch between the tables by selecting the measurement characteristics).

5. We change the voltage between the collector and the emitter UCE) after saving the experimental data in the table and we repeat the measurement (see paragraphs 15 to 16).

6. The experimental values can be immediately plotted on a graph (Show graph button). This option can be used for continuous control of the shape of the measured dependence. This is a bundle of dependencies set by base current IB in case of output characteristics. Displaying experimental values will be important until after measuring several dependencies for different values of base current IB.

7. We will change the value of the base current after measuring a dependency – dependency IC and UCE for const. IB – and measure the same thing again. In other words: We repeat the measurement from point 14. to 18. with another base current.

8. We save the experimental data to the disk of the PC and stop the remote task after measuring the required data.

9. We open the resulting file in a spreadsheet program (MS Excel, Oo Calc, Kingsoft Spreadsheets…).

10. We divide the experimental data for each series according to the base current IB specified in the spreadsheet. We plot all dependencies in the same diagram. We create the bundle of output characteristics where the base current IB is a parameter.

11. We compare the shapes of the obtained dependencies, plotted in a common graph, with the theory.

12. We compare the magnitude of the base current IB and the collector current IC at transistor saturation ("constant" part of the characteristic). We compare the values of the mutual ratios of the currents with the value of the current gain factor β obtained from the transfer characteristic.