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| university:courses:electronics:electronics-lab-nr [15 Dec 2013 02:53] – major rewrite Doug Mercer | university:courses:electronics:electronics-lab-nr [11 Jan 2021 11:02] (current) – Fixed bad link for OP482 Ioana Chelaru |
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| =====Materials:===== | =====Materials:===== |
| | ADALM2000 Active Learning Module\\ |
| Analog Discovery Lab hardware\\ | |
| Solder-less breadboard, and jumper wire kit\\ | Solder-less breadboard, and jumper wire kit\\ |
| 1 - 4.7 KΩ resistor\\ | 1 - 4.7 KΩ resistor\\ |
| =====Directions Step 1:===== | =====Directions Step 1:===== |
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| The zener diode ( 1N4735 ) supplied in the Analog Parts Kit is a 6.1 volt diode. 6.1 volts is much too high a reverse breakdown voltage to build this circuit using the fixed +/- 5 volt power supplies of the Analog Discovery hardware. The forward voltage of an LED is in the range of 1.6 to 2.0 volts depending on the color of the diode. While not a proper reference diode, we can build the circuit for instructional purposes using the LEDs from the Analog Parts Kit. | The zener diode ( 1N4735 ) supplied in the ADALP2000 Analog Parts Kit is a 6.1 volt diode. 6.1 volts is much too high a reverse breakdown voltage to build this circuit using the fixed +/- 5 volt power supplies of the ADALM2000 hardware. The forward voltage of an LED is in the range of 1.6 to 2.0 volts depending on the color of the diode. While not a proper reference diode, we can build the circuit for instructional purposes using the LEDs from the ADALP2000 Analog Parts Kit. |
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| Build both of the versions of the circuits in figure 1(a) and 1(b) as shown in figure 2 on your solder-less breadboard. Use two LEDs preferably of the same color. Green LEDs will have a higher forward voltage drop than red or yellow. We want the diode current, I<sub>D</sub>, to be about 1 mA and the as close to this same value in both versions of the circuit. In the case (b) I<sub>D</sub> will be +5/R<sub>4</sub> so a 4.7 KΩ resistor would give about 1 mA. In case (a) I<sub>D</sub> will be (+5-V<sub>D</sub>)/R<sub>3</sub>. If we use 2 V as an estimate for V<sub>D</sub>, then R<sub>3</sub> would be around 3 KΩ. You can get 3 KΩ by connecting two 1.5 KΩ resistors from the Parts Kit in series. Also for case (a) we need to pick values for R<sub>1</sub> and R<sub>2</sub>. We want the current in R<sub>1</sub> to be much smaller than the current in R<sub>3</sub>. So setting R<sub>1</sub> and R<sub>2</sub> to a much higher value such as 20 KΩ should satisfy that condition. | Build both of the versions of the circuits in figure 1(a) and 1(b) as shown in figure 2 on your solder-less breadboard. Use two LEDs preferably of the same color. Green LEDs will have a higher forward voltage drop than red or yellow. We want the diode current, I<sub>D</sub>, to be about 1 mA and the as close to this same value in both versions of the circuit. In the case (b) I<sub>D</sub> will be +5/R<sub>4</sub> so a 4.7 KΩ resistor would give about 1 mA. In case (a) I<sub>D</sub> will be (+5-V<sub>D</sub>)/R<sub>3</sub>. If we use 2 V as an estimate for V<sub>D</sub>, then R<sub>3</sub> would be around 3 KΩ. You can get 3 KΩ by connecting two 1.5 KΩ resistors from the Parts Kit in series. Also for case (a) we need to pick values for R<sub>1</sub> and R<sub>2</sub>. We want the current in R<sub>1</sub> to be much smaller than the current in R<sub>3</sub>. So setting R<sub>1</sub> and R<sub>2</sub> to a much higher value such as 20 KΩ should satisfy that condition. |
| =====Hardware setup:===== | =====Hardware setup:===== |
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| Open the voltage source control and the voltmeter instrument windows from the main screen of the Waveforms software. A DMM, if available, could be useful to more accurately measure the DC voltages in the circuit than the Waveforms voltmeter instrument. | Open the voltage supply control and the voltmeter instrument windows from the Scopy software. A DMM, if available, could be useful to more accurately measure the DC voltages in the circuit than the Scopy voltmeter instrument. |
| | {{ :university:courses:electronics:anr_f2bb.png? |}} |
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| | <WRAP centeralign> Figure 3 LED based volt regulator breadboard connections </WRAP> |
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| =====Procedure:===== | =====Procedure:===== |
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| Turn on both the positive and negative power supplies. Observe the two voltages at -V<sub>REF</sub>, pins 8 and 14 of the op amp and at +V<sub>REF</sub> on the LED. | Turn on both the positive and negative power supplies. Observe the two voltages at -V<sub>REF</sub>, pins 8 and 14 of the op amp and at +V<sub>REF</sub> on the LED. |
| | {{ :university:courses:electronics:anr_f2ss.png?600 |}} |
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| | <WRAP centeralign> Figure 4 Scopy voltmeter</WRAP> |
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| =====Questions:===== | =====Questions:===== |
| {{ :university:courses:electronics:anr_f3.png?600 |}} | {{ :university:courses:electronics:anr_f3.png?600 |}} |
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| <WRAP centeralign> Figure 3, NPN shunt band-gap reference example </WRAP> | <WRAP centeralign> Figure 5 NPN shunt band-gap reference example </WRAP> |
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| =====Hardware setup:===== | =====Hardware setup:===== |
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| The setup is the same as step 1. | The setup is the same as step 1. |
| | {{ :university:courses:electronics:anr_f6.png? |}} |
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| | <WRAP centeralign> Figure 6 LED based volt regulator example </WRAP> |
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| =====Procedure:===== | =====Procedure:===== |
| ====Testing supply headroom==== | ====Testing supply headroom==== |
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| To test the headroom requirements for +V<sub>DD</sub>, disconnect the fixed positive power supply from +V<sub>DD</sub> and remove any supply decoupling capacitors. Be sure to turn off the power supplies before making any changes or additions to your breadboard. Now connect +V<sub>DD</sub> to AWG 1. Set AWG 1 to trapezium (trapezoid) waveform at 100 Hz. Set the amplitude to 2.5V with a 2.5V offset for a 0 to +5V swing. Connect scope channel 1 to the output of AWG1 and connect scope channel 2 to -V<sub>REF</sub> of the first example circuit at pin 14 of the OP482. Use the oscilloscope instrument in the XY mode, scope channel for X and scope channel 2 for Y. Start AWG 1 and turn on the fixed negative 5V power supply. Record the minimum +V<sub>DD</sub> voltage where -V<sub>REF</sub> starts to remain constant at -1.25V. | To test the headroom requirements for +V<sub>DD</sub>, disconnect the fixed positive power supply from +V<sub>DD</sub> and remove any supply decoupling capacitors. Be sure to turn off the power supplies before making any changes or additions to your breadboard. Now connect +V<sub>DD</sub> to AWG 1. Set AWG 1 to trapezium (trapezoid) waveform at 100 Hz. Set the amplitude to 5V peak-to-peak with a 2.5V offset for a 0 to +5V swing. Connect scope channel 1 to the output of AWG1 and connect scope channel 2 to -V<sub>REF</sub> of the first example circuit at pin 14 of the OP482. Use the oscilloscope instrument in the XY mode, scope channel for X and scope channel 2 for Y. Start AWG 1 and turn on the fixed negative 5V power supply. Record the minimum +V<sub>DD</sub> voltage where -V<sub>REF</sub> starts to remain constant at -1.25V. |
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| To test the headroom requirements for -V<sub>SS</sub>, reconnect +V<sub>DD</sub> to the fixed positive power supply. Disconnect the fixed negative power supply from -V<sub>SS</sub> and remove any supply decoupling capacitors. Now connect -V<sub>SS</sub> to AWG 1. Set the amplitude to 2.5V with a -2.5V offset for a 0 to -5V swing. Start AWG 1 and turn on the fixed positive 5V power supply. Repeat your measurements of pins 14 of the OP482 recording the lowest value for -V<sub>SS</sub> where the reference voltage is constant. | |
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| =====Questions:===== | |
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| | To test the headroom requirements for -V<sub>SS</sub>, reconnect +V<sub>DD</sub> to the fixed positive power supply. Disconnect the fixed negative power supply from -V<sub>SS</sub> and remove any supply decoupling capacitors. Now connect -V<sub>SS</sub> to AWG 1. Set the amplitude to 5V peak-to-peak with a -2.5V offset for a 0 to -5V swing. Start AWG 1 and turn on the fixed positive 5V power supply. Repeat your measurements of pins 14 of the OP482 recording the lowest value for -V<sub>SS</sub> where the reference voltage is constant. |
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| =====Directions Step 3:===== | =====Directions Step 3:===== |
| {{ :university:courses:electronics:anr_f4.png?600 |}} | {{ :university:courses:electronics:anr_f4.png?600 |}} |
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| <WRAP centeralign> Figure 4, NPN three terminal band-gap reference example </WRAP> | <WRAP centeralign> Figure 7 NPN three terminal band-gap reference example </WRAP> |
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| =====Hardware setup:===== | =====Hardware setup:===== |
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| The setup is the same as step 1. | The setup is the same as step 1. |
| | {{ :university:courses:electronics:anr_f8.png? |}} |
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| | <WRAP centeralign> Figure 8 LED based volt regulator example </WRAP> |
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| =====Procedure:===== | =====Procedure:===== |
| Repeat the supply headroom tests you did in Step 2 for this configuration. Are there any differences? | Repeat the supply headroom tests you did in Step 2 for this configuration. Are there any differences? |
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| | <WRAP round download> |
| | **Resources:** |
| | * Fritzing files: [[downgit>education_tools/tree/master/m2k/fritzing/neg_voltage_ref_bb | neg_voltage_ref_bb]] |
| | * LTspice files: [[downgit>education_tools/tree/master/m2k/ltspice/neg_voltage_ref_ltspice | neg_voltage_ref_ltspice]] |
| | </WRAP> |
| ====For further reading:==== | ====For further reading:==== |
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| [5] [[university:courses:electronics:electronics-lab-7|Activity 7. Zero gain amplifier (BJT)]]\\ | [5] [[university:courses:electronics:electronics-lab-7|Activity 7. Zero gain amplifier (BJT)]]\\ |
| [6] [[university:courses:electronics:electronics-lab-8|Activity 8. Stabilized current source (BJT)]]\\ | [6] [[university:courses:electronics:electronics-lab-8|Activity 8. Stabilized current source (BJT)]]\\ |
| [[http://www.analog.com/static/imported-files/data_sheets/OP282_OP482.pdf]] OP482 datasheet | [[adi>OP482]] datasheet |
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| Return to Lab Activity [[university:courses:electronics:labs|Table of Contents]] | Return to Lab Activity [[university:courses:electronics:labs|Table of Contents]] |
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| ====Appendix:==== | ====Appendix:==== |
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