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university:courses:electronics:electronics-lab-loop-gain [27 Mar 2019 12:15] – add ltspice files Antoniu Miclausuniversity:courses:electronics:electronics-lab-loop-gain [21 Jan 2020 15:20] – ↷ Links adapted because of a move operation Cristina Suteu
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 =====Directions:===== =====Directions:=====
  
-Build the measurement setup as shown in figure 3 below. Remember to supply power to the op amp, +5 V to pin 7 and -5V to pin 4 with 0.1uF capacitors used to de-couple the Vp and Vn power supplies ( not shown in schematic diagram for simplicity ). If you are using the HPH1-1400L transformer for T<sub>1</sub> you should connect three of the 6 windings in series for the primary and the remaining three windings in series for the secondary ( see this [[university:courses:electronics:comms-lab-transformers|activity on transformers]] for more details ). Resistor R<sub>1</sub> is set to 1 KΩ and R<sub>2</sub> is either 1 KΩ or 10 KΩ to test different loop gains with the three different op-amps. Voltage divider R<sub>4</sub> and R<sub>5</sub> serves two purposes. First the 10 Ω R<sub>4</sub> matches the impedance of the resistor inserted in the feedback loop, R<sub>3</sub>. The AWG in the ADALM2000 cannot directly drive the 10 Ω resistor so the 100 Ω R<sub>5</sub> increases the load resistance to a value high enough for the AWG to safely drive. The attenuation of the divider also allows us to set the amplitude of the AWG high enough to provide a low noise signal while still injecting a small signal into the loop.+Build the measurement setup as shown in figure 3 below. Remember to supply power to the op amp, +5 V to pin 7 and -5V to pin 4 with 0.1uF capacitors used to de-couple the Vp and Vn power supplies ( not shown in schematic diagram for simplicity ). If you are using the HPH1-1400L transformer for T<sub>1</sub> you should connect three of the 6 windings in series for the primary and the remaining three windings in series for the secondary ( see this [[university:labs:m2k:comms_lab_transformers|activity on transformers]] for more details ). Resistor R<sub>1</sub> is set to 1 KΩ and R<sub>2</sub> is either 1 KΩ or 10 KΩ to test different loop gains with the three different op-amps. Voltage divider R<sub>4</sub> and R<sub>5</sub> serves two purposes. First the 10 Ω R<sub>4</sub> matches the impedance of the resistor inserted in the feedback loop, R<sub>3</sub>. The AWG in the ADALM2000 cannot directly drive the 10 Ω resistor so the 100 Ω R<sub>5</sub> increases the load resistance to a value high enough for the AWG to safely drive. The attenuation of the divider also allows us to set the amplitude of the AWG high enough to provide a low noise signal while still injecting a small signal into the loop.
  
 {{ :university:courses:electronics:amlg_f3.png?600 |}} {{ :university:courses:electronics:amlg_f3.png?600 |}}
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 The green squares indicate where to connect the ADALM2000 module AWG, scope channels and power supplies. Be sure to turn on the power supplies only after you double check your wiring. The green squares indicate where to connect the ADALM2000 module AWG, scope channels and power supplies. Be sure to turn on the power supplies only after you double check your wiring.
  
-Open the voltage supply control window to turn on and off the fixed +5 and -5 volt power supplies. Open the Network Analyzer Instrument and set the sweep to start at 10 KHz and stop at 5 MHz. The Max gain should be set to 1X. Set the Amplitude to 3V and the Offset to zero volts. Under the Bode scale set the magnitude top to 40 dB and range to 80 dB. Set the phase top to 180º and range to 360º. Under scope channels click on use channel 1 as reference. Set the number of steps to 500.+Open the voltage supply control window to turn on and off the fixed +5 and -5 volt power supplies. Open the Network Analyzer Instrument and set the sweep to start at 10 KHz and stop at 5 MHz. The Max gain should be set to 1X. Set the Amplitude to 3V  peak-to-peak and the Offset to zero volts. Under the Bode scale set the magnitude top to 40 dB and range to 80 dB. Set the phase top to 180º and range to 360º. Under scope channels click on use channel 1 as reference. Set the number of steps to 500.
  
 <WRAP centeralign>{{:university:courses:electronics:loop_gain-bb.png|}}</WRAP> <WRAP centeralign>{{:university:courses:electronics:loop_gain-bb.png|}}</WRAP>
university/courses/electronics/electronics-lab-loop-gain.txt · Last modified: 03 Nov 2021 20:27 by Doug Mercer

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