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electrical_engineering_and_electronics_1:block21 [2025/12/14 22:16] – mexleadminelectrical_engineering_and_electronics_1:block21 [2026/01/10 10:05] (current) – mexleadmin
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 ====== Block 21 — Op-Amp Basics ====== ====== Block 21 — Op-Amp Basics ======
  
-===== Learning objectives =====+===== 21.0 Intro ===== 
 + 
 +==== 21.0.1 Learning objectives ====
 <callout> <callout>
 After this 90-minute block, you can After this 90-minute block, you can
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 </callout> </callout>
  
-===== Preparation at Home =====+==== 21.0.2 Preparation at Home ====
  
 Well, again  Well, again 
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   * ...   * ...
  
-===== 90-minute plan =====+==== 21.0.3 90-minute plan ====
   - Warm-up (10 min):   - Warm-up (10 min):
     - Hook: audio amplifier clipping example (undistorted vs overdriven waveform/spectrum) → why “ideal amplification” is not automatic.     - Hook: audio amplifier clipping example (undistorted vs overdriven waveform/spectrum) → why “ideal amplification” is not automatic.
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     - Common pitfalls checklist (below).     - Common pitfalls checklist (below).
  
-===== Conceptual overview =====+==== 21.0.4 Conceptual overview ====
 <callout icon="fa fa-lightbulb-o" color="blue"> <callout icon="fa fa-lightbulb-o" color="blue">
   - Think of an op-amp as a **differential voltage sensor + powerful output stage**:   - Think of an op-amp as a **differential voltage sensor + powerful output stage**:
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 </callout> </callout>
  
-===== Core content =====+===== 21.1 Core content =====
  
 <WRAP>  <WRAP> 
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 <WRAP> <WRAP>
  
-==== Introductory example ====+==== 21.1.1 Introductory example ====
  
 Acoustic amplifiers, such as those found in mobile phones, laptops, or hi-fi systems, often exhibit an unpleasant characteristic when heavily amplified: the previously undistorted signal is no longer passed on as usual, but [[https://en.wikipedia.org/wiki/Total_harmonic_distortion#Definitions_and_examples|clatters]]. It is distorted in such a way that it no longer sounds pleasant. Acoustic amplifiers, such as those found in mobile phones, laptops, or hi-fi systems, often exhibit an unpleasant characteristic when heavily amplified: the previously undistorted signal is no longer passed on as usual, but [[https://en.wikipedia.org/wiki/Total_harmonic_distortion#Definitions_and_examples|clatters]]. It is distorted in such a way that it no longer sounds pleasant.
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-==== Circuit symbols and basic circuitry ====+==== 21.1.2 Circuit symbols and basic circuitry ====
  
 This chapter deals with operational amplifiers. One application for these are the measurement of voltages, currents, and resistances. \\ These values must be determined very precisely in some applications, for example for accurate temperature measurement. In this case, amplification of the measurement signals is useful and necessary. This chapter deals with operational amplifiers. One application for these are the measurement of voltages, currents, and resistances. \\ These values must be determined very precisely in some applications, for example for accurate temperature measurement. In this case, amplification of the measurement signals is useful and necessary.
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 ~~PAGEBREAK~~ ~~CLEARFIX~~ ~~PAGEBREAK~~ ~~CLEARFIX~~
-==== Basic Equation / Golden Rules ====+==== 21.1.3 Basic Equation / Golden Rules ====
  
 The operational amplifier is a voltage amplifier. It simply measures on one side the voltage (like a voltmeter) and provides an amplified voltage on its output (like a voltage source). \\  The operational amplifier is a voltage amplifier. It simply measures on one side the voltage (like a voltmeter) and provides an amplified voltage on its output (like a voltage source). \\ 
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 ~~PAGEBREAK~~ ~~CLEARFIX~~ ~~PAGEBREAK~~ ~~CLEARFIX~~
-==== Feedback ====+==== 21.1.4 Feedback ====
  
 One of the fundamental principles of control engineering, digital technology, and electronics is **feedback**. \\ One of the fundamental principles of control engineering, digital technology, and electronics is **feedback**. \\
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-===== Common pitfalls =====+===== 21.3 Common pitfalls =====
   * **Mixing up the inputs:** confusing the inverting input $U_{\rm m}$ (minus) with the non-inverting input $U_{\rm p}$ (plus). A wrong sign flips the whole behavior.   * **Mixing up the inputs:** confusing the inverting input $U_{\rm m}$ (minus) with the non-inverting input $U_{\rm p}$ (plus). A wrong sign flips the whole behavior.
   * **Wrong differential voltage:** forgetting that $U_{\rm D}$ = $U_{\rm p}$ - $U_{\rm m}$.   * **Wrong differential voltage:** forgetting that $U_{\rm D}$ = $U_{\rm p}$ - $U_{\rm m}$.
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-===== Learning Questions =====+===== 21.4 Learning Questions =====
  
   * Explain the difference between the unipolar and bipolar power supply of an opamp.   * Explain the difference between the unipolar and bipolar power supply of an opamp.
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   * What is the basic equation of the opamp?   * What is the basic equation of the opamp?
  
-===== Exercises =====+===== 21.5 Exercises =====
  
 <panel type="info" title="Exercise 1.3.2 Calculations for negative feedback"> <panel type="info" title="Exercise 1.3.2 Calculations for negative feedback">
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 </WRAP></WRAP></panel> </WRAP></WRAP></panel>
  
-<panel type="info" title="Exercise 21.1 — Op-amp basics: symbols and signs">+<panel type="info" title="Exercise 21.1 Op-amp basics: symbols and signs">
   * Given an operational amplifier symbol, label the following quantities:   * Given an operational amplifier symbol, label the following quantities:
       - non-inverting input voltage $U_{\rm p}$,       - non-inverting input voltage $U_{\rm p}$,
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 </panel> </panel>
  
-<panel type="info" title="Exercise 21.2 — Differential vs single-ended thinking">+<panel type="info" title="Exercise 21.2 Differential vs single-ended thinking">
 An op-amp has $A_{\rm D}=150{'}000$ and is powered from $\pm 12\,\rm V$. An op-amp has $A_{\rm D}=150{'}000$ and is powered from $\pm 12\,\rm V$.
   - Compute $U_{\rm O}$ for $U_{\rm p}=1.002\,\rm V$ and $U_{\rm m}=1.000\,\rm V$ (ideal equation).   - Compute $U_{\rm O}$ for $U_{\rm p}=1.002\,\rm V$ and $U_{\rm m}=1.000\,\rm V$ (ideal equation).
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 </panel> </panel>
  
-<panel type="info" title="Exercise 21.3 — Unipolar supply and output biasing">+<panel type="info" title="Exercise 21.3 Unipolar supply and output biasing">
 An op-amp operates from a unipolar supply $0\,\rm V$ to $9\,\rm V$. An op-amp operates from a unipolar supply $0\,\rm V$ to $9\,\rm V$.
   - What output voltage corresponds to “zero differential input” in a typical unipolar configuration?   - What output voltage corresponds to “zero differential input” in a typical unipolar configuration?
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 </panel> </panel>
  
-<panel type="info" title="Exercise 21.4 — Unipolar supply and virtual ground intuition">+<panel type="info" title="Exercise 21.4 Unipolar supply and virtual ground intuition">
 An op-amp uses a unipolar supply $0\,\rm V \dots 10\,\rm V$. \\ An op-amp uses a unipolar supply $0\,\rm V \dots 10\,\rm V$. \\
 If you want to amplify a small sinus signal centered around $0\,\rm V$, why is it a problem to connect it directly to an input? If you want to amplify a small sinus signal centered around $0\,\rm V$, why is it a problem to connect it directly to an input?
 </panel> </panel>
  
-<panel type="info" title="Exercise 21.5 — Classify feedback (fast diagnosis)">+<panel type="info" title="Exercise 21.5 Classify feedback (fast diagnosis)">
   * For each statement, mark **true/false** and correct the false ones:   * For each statement, mark **true/false** and correct the false ones:
       -  Feeding back a fraction of the output to the inverting input always creates negative feedback.       -  Feeding back a fraction of the output to the inverting input always creates negative feedback.
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 </panel> </panel>
  
-<panel type="info" title="Exercise 21.6 — Saturation and clipping reasoning">+<panel type="info" title="Exercise 21.6 Saturation and clipping reasoning">
 An op-amp is powered from $\pm 5\,\rm V$ (bipolar). The output swing is limited to about $\pm 4\,\rm V$. An op-amp is powered from $\pm 5\,\rm V$ (bipolar). The output swing is limited to about $\pm 4\,\rm V$.
   - If $U_{\rm D}=+50\,\mu\rm V$ and $A_{\rm D}=200{,}000$, compute the ideal $U_{\rm O}$. Is saturation expected?   - If $U_{\rm D}=+50\,\mu\rm V$ and $A_{\rm D}=200{,}000$, compute the ideal $U_{\rm O}$. Is saturation expected?
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 </panel> </panel>
  
-<panel type="info" title="Exercise 21.7 — Input bias currents (qualitative + estimate)">+<panel type="info" title="Exercise 21.7 Input bias currents (qualitative + estimate)">
 A sensor with source resistance $R_{\rm S}=1\,\rm M\Omega$ drives the non-inverting input. \\ A sensor with source resistance $R_{\rm S}=1\,\rm M\Omega$ drives the non-inverting input. \\
 The real op-amp dows not only show an internal resistance, but also a small current source on the input pins. \\ The real op-amp dows not only show an internal resistance, but also a small current source on the input pins. \\
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 </panel> </panel>
  
-<panel type="info" title="Exercise 21.8 — Output current limit and load selection">+<panel type="info" title="Exercise 21.8 Output current limit and load selection">
 A real op-amp can supply at most $I_{\rm O,max}=20\,\rm mA$. \\  A real op-amp can supply at most $I_{\rm O,max}=20\,\rm mA$. \\ 
 It is intended to drive a load resistor $R_{\rm L}$ from an output voltage of $U_{\rm O}=3\,\rm V$. It is intended to drive a load resistor $R_{\rm L}$ from an output voltage of $U_{\rm O}=3\,\rm V$.