PART7 Basic Circuit of Semiconductor

Experiment 1 : Characteristic of Diode

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PART7Basic Circuit of Semiconductor

Experiment Purpose

  • 1.Investigate characteristic of diode and zener diode.
  • 2.Understand characteristic of rectifier circuit and filter circuit.
  • 3.Understand characteristic of transistor.
  • 4.Understand characteristic of FET/SCR/UJT.
  • 5.Understand characteristic of LED.
Fig. 7-1AReS-EI-M07 Basic semiconductor Module

Experiment 1 :Characteristic of Diode

Theory

Semiconductor diode can pass the current to one direction while it cannot to the opposite direction. This is because while the forward resistance is low, the reverse resistance is very high. All semiconductor diodes usually are one-directional.

fig7-2

Fig. 7-2Junction Diode Impressed by Forward and Reverse Voltages

① Forward Current

As in fig.7-2(a), if + pole is connected to p type and - pole to n type of the p-n junction diode, it is said that the forward voltage or forward bias is applied. Here, big current, that is, forward current flows through the diode. The hole of p area flows actively to n area, and the electron of n area to p area so the big current can flow from p area to n area.

② Reverse Current

As in fig.7-2(b), if + pole is connected to n type and - pole to p type of p-n junction diode, it is said that the reverse voltage or reverse bias is applied. Here, very faint current, that is, reverse saturation current flows from n area to p area through the diode. This current reaches its maximum easily with low reverse voltage and even though the voltage gets higher it does not get bigger so is called reverse saturation current.

Current Formula of Diode

fig7-3

Fig. 7-3Forward v-i Characteristic of Common Junction Diode

The current flowing on the ideal diode can be expressed as below.

I = I_s (e^V/nV_T -1 )

In the formula above, VT=T/11,600(26mV in room temperature), T is absolute temperature, IS is reverse saturation current and n is an integer that has 1 value to Ge and 2 value to Si. In the formula above, if V=0 then I=0, and if V > 0.1V, according to I≅Is ε40V, I increases in quotient, and if V < -0.1V, I≅Is and it is in saturated status. Fig.7-3 shows the v-i characteristic of junction diode and fig.(b) shows that of germanium diode and silicon diode. As in fig.(b), the current increases radically at 0.7V in case of Si diode and over 0.2V in case of Ge diode. This voltage is called the cutin voltage or the threshold voltage of the diode.

Experiment Process

fig7-4


(a) Characteristic of forward current

fig7-4


(b) Characteristic of reverse current Fig. 7-4Diode Characteristic

1. Use Block a of M07 to measure characteristic of forward and reverse current of the diode.

2. To measure forward current of Si diode, connect the separate digital multimeter(ammeter) and compose a circuit as in fig.7-4(a).
- Adjust VR1 and change the input voltage as in table 7-1, and measure the forward current (IF) and the voltage between both ends of D1 and record the result.

3. To measure reverse current of Si diode, connect the separate digital multimeter(ammeter) and compose a circuit as in fig.7-4(b). Adjust VR1 and change the input voltage as in table 7-1, and measure the reverse current (IR) and record the result.

tab1

Experiment 7-1.1 Diode DC Characteristic Measurement (in Block a of M07, compose a circuit as in fig.7-4.)

When R1= 1kΩ

1.Connection(Block a of M07)
1.Circuit Connection

In Block a, connect between left terminal of R1 and center(middle) terminal of VR1 with yellow line.

2.Power Connection

Connect between Variable Power V1 terminal of M07 board and upper terminal of VR1 of Block a with red line, and between COM terminal and the earthing terminal with black line.

3.Measuring Instrument Connection

Ammeter Connection

Measure by using the current measurement function of separate Digital Multimeter.

Measuring the current (IF) on the diode: Connect the red line of Digital Multimeter to the right terminal of SW1 of Block a, and the black line to upper terminal of the diode D1.

Voltmeter Connection

Measuing input voltage: In Block a, connect between the left terminal of the resistance R1 and A+ terminal of Signal Input CH A on front panel with red line, and between the earthing terminal and A- terminal with black line.

Measuring the voltage (VD) of diode’s both ends: In Block a, connect between upper terminal of the diode D1 and B+ terminal of Signal Input CH B on front with red line, and between the earthing terminal and Low terminal with black line.

2.Wiring Diagram
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3.Measurement
  1. Forward Characteristic When R1= 1kΩ
    1Choose analog output at the left menu of Touch LCD panel, choose 3 CH DC tab

    Click button_arrow on the right of DC Voltage1 to set up 10v

    Click on to apply the output of DC 10V to the input of Block a.

    3CHDC

  2. 2Choose analog input at the left menu of Touch LCD panel and click Voltage & Ampere Meter tab.

    Click voltage, dc, av at CH A and CH B.

  3. 3Adjust VR1 and change the input voltage as in table 7-1, and record the forward current (IF) value indicated at the separate digital multimeter, the input voltage(CH A) measured at Voltage & Ampere Meter, and the voltage (VD) between both ends of the diode(CH B) in table 7-1.

    VoltAndAmpereMeter

  4. 4After the measurement, click on red to cut off the output.
  5. Reverse Characteristic When R1= 1kΩ
    5Choose variable power at the left menu of Touch LCD panel, choose 3 CH DC tab.

    Click button_arrow on the right of DC Voltage1 to set up 10v .

    Click inv to make -10V.

    3CHDC

    Click on to apply the output of DC -10V to the input of Block a.

  6. 6Change the input voltage as (-VD) in table 7-1, and record the reverse current (IF) value indicated at the separate digital multimeter, the input voltage(CH A) measured at Voltage & Ampere Meter, and the reverse voltage (-VD) between both ends of the diode(CH B) in table 7-1.
  7. 7After the measurement, click on red to cut off the output.

When R2=470Ω

1.Connection(Block a of M07)
1.Circuit Connection

In Block a, connect between the left terminal of R2 and center(middle) terminal of VR1 with yellow line.

2.Power Connection is same as When R1=1kΩ >1. Connection.
3.Measuring Instrument Connection is same as When R1=1kΩ >1. Connection.
2.Wiring Diagram
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3.Measurement
  1. 1The Measurement is same as When R1=1kΩ>1. Measurement, and record the measured values of forward and reverse characteristic in table 7-1.
  2. 2After the measurement, click on red to cut off the output.
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Experiment Result Report

result
Characteristic of Diode
1. Experiment Result Table

Table 7-1

result_table
Input Voltage | Current Si Diode(1kΩ Circuit)Si Diode(470Ω Circuit)
Forward[IF]VDReverse[IR]-VD Forward[IF]VDReverse[IR]-VD
0.1V 00.10     
0.2V 00.20     
0.3V 10uA0.30     
0.4V 11uA0.39     
0.5V 52uA0.45     
0.6V 0.11mA0.48     
0.7V 0.18mA0.50     
0.8V 0.27mA0.52     
0.9V 0.35mA0.53     
1.0V 0.40mA0.552uA-1.0 -1.0
2.0V 1.40mA0.603uA-2.0 -2.0
3.0V 2.40mA0.626uA-3.0 -3.0
4.0V 3.40mA0.63-4.0 -4.0
5.0V 4.40mA0.63-5.0 -5.0
6.0V 5.40mA0.66-6.0 -6.0
7.0V 6.20mA0.66-7.0 -7.0
8.0V 7.40mA0.67-8.0 -8.0
9.0V 8.60mA0.68-9.0 -9.0
10.0V 19uA-10 -10
2. Review and Explanation
1) When measuring forward characteristic of Si diode and when the input voltage is 10V, calculate the flowing current for the case of R1(1kΩ) and that of R2(470Ω), and compare it with the current IF which flows through Si diode.
2) What is bulk resistance? Calculate the bulk resistance using the experiment above.
3) Using the measured values in table 7-1, draw a forward characteristic curve of the diode.

section paper

(Reverse)section paper

4) Compare the drawn characteristic curve with the characteristic curve suggested in the theory.
3. Discuss the experiment result.