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--- lab05_en:inverting_op-amp_basics_amplification [2026/03/31 11:34] – [Inverting Operational Amplifier] mexleadmin
+++ lab05_en:inverting_op-amp_basics_amplification [2026/04/28 16:21] (current) – [Analysis of inverting input currents] mexleadmin
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 ==== Inverting Operational Amplifier ====
+== Gain of Op-Amp ==
 Build the following circuit in <imgref Fig-20_inverting_op-amp> with the power supply and a multimeter.
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 <imgcaption Fig-20_inverting_op-amp | Inverting Op-Amp> </imgcaption>
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-Values of the components:
-$U_{\rm DD}{\rm=10~V},~U_{\rm SS}{\rm=-10~V},~R_{\rm 2}{\rm=100~k\Omega}$
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+$U_{\rm DD}{\rm~=10~V},~U_{\rm SS}{\rm~=-10~V},~R_{\rm 1}{\rm~=10~k\Omega}$
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+Calculate the necessary value for $R_{\rm 2}$, so that the Output $U_{\rm OUT}$ is +5 V.
+Use the supply voltage of the operational amplifier for $U_{\rm IN}$.
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+$U_{\rm IN}{\rm~=}$
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+$R_{\rm 2}{\rm~=}$
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+== Analysis of inverting input currents ==
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+{{drawio>lab05:Fig-30_inverting_op-amp_inv_input.svg}}
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+<imgcaption Fig-30_inverting_op-amp_inv_input | Inverting Op-Amp: Analysis of currents of the inverting input> </imgcaption>
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+$U_{\rm DD}{\rm~=10~V},~U_{\rm SS}{\rm~=-10~V},~R_{\rm 1}{\rm~=10~k\Omega}$\\ \\
+Use the values from <imgref Fig-20_inverting_op-amp> for $U_{\rm IN},~U_{\rm OUT},~R_{\rm 2}$.
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+Complete the arrows in the scematic of the circuit.\\
+Determine the the currents $I_{\rm 1}$ and $I_{\rm 2}$ indirectly by measuring the voltage across known resistors\\
+and calculate the algebraic sum of the currents at node $N_{\rm {12}}$ using Kirchhoff’s Current Law (KCL).
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+$U_{\rm 1}{\rm~=}$
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+$U_{\rm 2}{\rm~=}$\\
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+$I_{\rm 1}{\rm~=}$
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+$I_{\rm 2}{\rm~=}$
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+$I_{\rm N12}{\rm~=}$
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+== Analysis of inverting input voltages ==
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+{{drawio>lab05:Fig-40_inverting_op-amp_inv_input_virt_gnd.svg}}
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+<imgcaption Fig-40_inverting_op-amp_inv_input_virt_gnd | Inverting Op-Amp: Analysis of virtual GND of the inverting input> </imgcaption>
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+$U_{\rm DD}{\rm~=10~V},~U_{\rm SS}{\rm~=-10~V},~R_{\rm 1}{\rm~=10~k\Omega}$\\ \\
+Use the values from <imgref Fig-20_inverting_op-amp> for $U_{\rm IN},~U_{\rm OUT},~R_{\rm 2}$.
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+Complete the reference arrows in the scematic of the circuit.\\
+Take the values for $U_{\rm 1},~U_{\rm 2},~U_{\rm OUT}$ from <imgref Fig-30_inverting_op-amp_inv_input>.\\
+Calculate the voltage $U_{12}$ using Kirchhoff's Voltage Law (KVL) within the circuit loop.\\
+Verify your calculated result by measuring $U_{12}$.
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+$U_{\rm 1}{\rm~=}$
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+$U_{\rm 2}{\rm~=}$
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+$U_{\rm OUT}{\rm~=}$
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+Calculated $U_{\rm 12}{\rm~=}$
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+Measured $U_{\rm 12}{\rm~=}$
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+Analyse the physical significance of the potential at $N_{12}$ relative to GND (defined as $U_{12}$) in the context of the operational amplifier's input configuration. What do you observe?\\
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-Set the signals listed in <tabref Table-1-Signals_V2> on the function generator and draw the corresponding oscilloscope screen images. The signal display on the oscilloscope should optimally fill the screen
+What happens if you short-circuit $R_2$ (the feedback resistor)?\\
+Experimentally verify this effect and explain the observed behavior regarding the output voltage.\\
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