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university:courses:electronics:electronics-lab-nr [27 Mar 2017 16:47]
dmercer [Materials:]
university:courses:electronics:electronics-lab-nr [23 Aug 2019 14:06] (current)
amiclaus
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 =====Directions Step 1:===== =====Directions Step 1:=====
  
-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. 
  
 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.
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 =====Hardware setup:===== =====Hardware setup:=====
  
-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?​ |}} 
 + 
 +<WRAP centeralign>​ Figure 3 LED based volt regulator breadboard connections </​WRAP>​
  
 =====Procedure:​===== =====Procedure:​=====
  
 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 |}}
 +
 +<WRAP centeralign>​ Figure 4 Scopy voltmeter</​WRAP>​
  
 =====Questions:​===== =====Questions:​=====
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 {{ :​university:​courses:​electronics:​anr_f3.png?​600 |}} {{ :​university:​courses:​electronics:​anr_f3.png?​600 |}}
  
-<WRAP centeralign>​ Figure ​3, NPN shunt band-gap reference example </​WRAP>​+<WRAP centeralign>​ Figure ​NPN shunt band-gap reference example </​WRAP>​
  
 =====Hardware setup:===== =====Hardware setup:=====
  
 The setup is the same as step 1. The setup is the same as step 1.
 +{{ :​university:​courses:​electronics:​anr_f6.png?​ |}}
 +
 +<WRAP centeralign>​ Figure 6 LED based volt regulator example </​WRAP>​
  
 =====Procedure:​===== =====Procedure:​=====
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 ====Testing supply headroom==== ====Testing supply headroom====
  
-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.
- +
-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. +
- +
-=====Questions:​=====+
  
 +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.
  
 =====Directions Step 3:===== =====Directions Step 3:=====
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 {{ :​university:​courses:​electronics:​anr_f4.png?​600 |}} {{ :​university:​courses:​electronics:​anr_f4.png?​600 |}}
  
-<WRAP centeralign>​ Figure ​4, NPN three terminal band-gap reference example </​WRAP>​+<WRAP centeralign>​ Figure ​NPN three terminal band-gap reference example </​WRAP>​
  
 =====Hardware setup:===== =====Hardware setup:=====
  
 The setup is the same as step 1. The setup is the same as step 1.
 +{{ :​university:​courses:​electronics:​anr_f8.png?​ |}}
 +
 +<WRAP centeralign>​ Figure 8 LED based volt regulator example </​WRAP>​
  
 =====Procedure:​===== =====Procedure:​=====
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 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?​
  
 +<WRAP round download>​
 +**Resources:​**
 +  * Fritzing files: [[ https://​minhaskamal.github.io/​DownGit/#/​home?​url=https://​github.com/​analogdevicesinc/​education_tools/​tree/​master/​m2k/​fritzing/​neg_voltage_ref_bb | neg_voltage_ref_bb]]
 +  * LTspice files: [[ https://​minhaskamal.github.io/​DownGit/#/​home?​url=https://​github.com/​analogdevicesinc/​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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 ====Appendix:​==== ====Appendix:​====
 +
  
  
university/courses/electronics/electronics-lab-nr.1490626066.txt.gz · Last modified: 27 Mar 2017 16:47 by dmercer