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| university:courses:electronics:electronics-lab-loop-gain [25 Jun 2020 22:07] – external edit | university:courses:electronics:electronics-lab-loop-gain [07 Apr 2021 14:38] – [Directions:] update link to transformers activity Cristina Suteu |
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| =====Directions:===== | =====Directions:===== |
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| 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. | 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:comms_lab_transformers_adalm2000|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. |
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| {{ :university:courses:electronics:amlg_f3.png?600 |}} | {{ :university:courses:electronics:amlg_f3.png?600 |}} |
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| <WRAP centeralign> Figure 3 Loop Gain Measurement setup </WRAP> | <WRAP centeralign> Figure 3 Loop Gain Measurement setup </ |
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| =====Hardware Setup:===== | =====Hardware Setup:===== |
