| Beide Seiten der vorigen Revision Vorhergehende Überarbeitung Nächste Überarbeitung | Vorhergehende Überarbeitung |
| circuit_design:uebung_3.3.1 [2021/11/27 22:56] – tfischer | circuit_design:uebung_3.3.1 [2023/03/28 10:06] (aktuell) – mexleadmin |
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| <WRAP right><panel type="default"> <imgcaption pic3_3_1 | passive and active shielding> </imgcaption> {{drawio>pic3_3_1 }} </panel></WRAP> | <WRAP right><panel type="default"> <imgcaption pic3_3_1 | passive and active shielding> </imgcaption> {{drawio>pic3_3_1 }} </panel></WRAP> |
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| Imagine that you work in the company " HHN Mechatronics & Robotics", which is a cheap mobile [[https://en.wikipedia.org/wiki/Electrocardiography|EKG]] – So you want to build a measuring device for the electrocardiogram or the cardiac voltage curve - for athletes and those in need. The measurement signal has only a few millivolts and microamps. In order to protect the signal from electromagnetic radiation on the way from the glued-on electrode to the evaluation electronics, a [[https://en.wikipedia.org/wiki/Electromagnetic_shielding|electromagnetic shielding]] placed around the line (see <imgref pic3_3_1>, above). However, since this creates a parasitic capacitor, a colleague suggested active shielding. The shielding is always kept at the measuring voltage that is applied to the line via a voltage follower (see <imgref pic3_3_1>, under). The parasitic capacitor is never charged due to this structure, since the same voltage prevails on both sides - there is no falsification of the signal. **It is important for the application that the voltage follower reacts quickly**. | Imagine that you work in the company "HHN Mechatronics & Robotics", which is a cheap mobile [[https://en.wikipedia.org/wiki/Electrocardiography|EKG]] – So you want to build a measuring device for the electrocardiogram or the cardiac voltage curve - for athletes and those in need. The measurement signal has only a few millivolts and microamps. In order to protect the signal from electromagnetic radiation on the way from the glued-on electrode to the evaluation electronics, a [[https://en.wikipedia.org/wiki/Electromagnetic_shielding|electromagnetic shielding]] placed around the line (see <imgref pic3_3_1>, above). However, since this creates a parasitic capacitor, a colleague suggested active shielding. The shielding is always kept at the measuring voltage that is applied to the line via a voltage follower (see <imgref pic3_3_1>, under). The parasitic capacitor is never charged due to this structure, since the same voltage prevails on both sides - there is no falsification of the signal. **It is important for the application that the voltage follower reacts quickly**. |
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| You are supervised with the design of this voltage follower and should use the available operational amplifiers $LM318$, $uA741$ and $uA776$analyze in the voltage follower circuit (see script page). | You are supervised with the design of this voltage follower and should use the available operational amplifiers $\rm LM318$, $\rm uA741$, and $\rm uA776$ analyze in the voltage follower circuit. |
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| Write a short report (problem description, circuit in TINA TI, resulsts, discussion) and use TINA TI for the solution. | Write a short report (problem description, circuit in TINA TI, results, discussion) and use TINA TI for the solution. |
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| - Recreate the circuit described above for a realistic operational amplifier in Tina. Use a voltage generator as a source [[https://en.wikipedia.org/wiki/Heaviside_step_function|unit step]] with the amplitude $U_A = 1.0 V$ . | - Recreate the circuit described above for a realistic operational amplifier in Tina. Use a voltage generator as a source [[https://en.wikipedia.org/wiki/Heaviside_step_function|unit step]] with the amplitude $U_\rm A = 1.0 ~\rm V$. |
| - Simulate over ''Analysis''>>''Transient…'' the time course for the specified operational amplifiers. \\ Determine the time that elapses until the initial value of $0.1 V$ for the first time $0.9 V$ achieved ($10%$ to $90%$ of the amplitude, too. It is called [[https://en.wikipedia.org/wiki/Rise_time|rise time]]). | - Simulate over ''Analysis''>>''Transient…'' the time course for the specified operational amplifiers. \\ Determine the time that elapses until the initial value of $0.1 ~\rm V$ for the first time $0.9 ~\rm V$ achieved ($10~\rm %$ to $90 ~\rm %$ of the amplitude, too. It is called [[https://en.wikipedia.org/wiki/Rise_time|rise time]]). |
| - Describe the passage of time in each case. Are there any other differences besides the rise time? | - Describe the passage of time in each case. Are there any other differences besides the rise time? |
| - Based on the information provided, which of the three op amps would you choose for the problem? | - Based on the information provided, which of the three op amps would you choose for the problem? |
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| In-depth information (not relevant for the homework): | In-depth information (not relevant to the exercise): |
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| * Paper [[https://pdfs.semanticscholar.org/f2b9/2ee5f3e3adb034e18ddb85bd3770dc8c2c29.pdf|on the Stability of Shield-Driver Circuits]] | * Paper [[https://pdfs.semanticscholar.org/f2b9/2ee5f3e3adb034e18ddb85bd3770dc8c2c29.pdf|on the Stability of Shield-Driver Circuits]] |