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| electrical_engineering_and_electronics_2:block11 [2026/06/01 23:18] – mexleadmin | electrical_engineering_and_electronics_2:block11 [2026/06/10 03:08] (current) – mexleadmin | ||
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| - | TBD | ||
| - | |||
| - | - Semiconductor components \\ (approx. 4 blocks, based on previous lectures on [[circuit_design: | ||
| - | - Fundamentals (conductors, | ||
| - | - Diodes (real characteristic curve, operating point, equivalent circuit) | ||
| - | - Zener diode | ||
| - | - LED | ||
| - | - Protective circuit with diodes | ||
| - | - Rectifier circuits (single-phase rectifier, center tap circuit, bridge rectifier, smoothing capacitor) | ||
| - | - Bipolar transistor (structure, designations, | ||
| - | - Transistor as a switch (circuit, switching times and behavior) | ||
| - | - MOSFET (structure, comparison with bipolar transistor) | ||
| - | - Optional: Transistor as an amplifier | ||
| - | |||
| - | |||
| ====== Block 11 — Semiconductor Fundamentals and Diodes ====== | ====== Block 11 — Semiconductor Fundamentals and Diodes ====== | ||
| Line 33: | Line 18: | ||
| \] | \] | ||
| at a qualitative level. | at a qualitative level. | ||
| - | * calculate simple diode operating points with a series resistor. | ||
| - | * identify basic diode types such as universal diodes, Z-diodes, and LEDs. | ||
| </ | </ | ||
| Line 93: | Line 76: | ||
| ===== Core content ===== | ===== Core content ===== | ||
| - | |||
| - | < | ||
| < | < | ||
| Line 127: | Line 108: | ||
| < | < | ||
| <panel type=" | <panel type=" | ||
| - | < | + | < |
| {{drawio> | {{drawio> | ||
| </ | </ | ||
| Line 238: | Line 219: | ||
| ==== Doping: n-type and p-type semiconductors ==== | ==== Doping: n-type and p-type semiconductors ==== | ||
| - | Doping increases the number of mobile charge carriers much more effectively: | + | Doping increases the number of mobile charge carriers much more effectively |
| * n-doping adds donor atoms and therefore additional mobile electrons, | * n-doping adds donor atoms and therefore additional mobile electrons, | ||
| * p-doping adds acceptor atoms and therefore additional mobile holes. | * p-doping adds acceptor atoms and therefore additional mobile holes. | ||
| - | < | + | Doping only works predictably when the semiconductor crystal is very pure. \\ |
| - | Doping only works predictably when the semiconductor crystal is very pure. | + | |
| The desired dopant atoms should dominate over unwanted impurities. | The desired dopant atoms should dominate over unwanted impurities. | ||
| - | </ | ||
| Doping means adding a very small amount of foreign atoms to the semiconductor crystal. | Doping means adding a very small amount of foreign atoms to the semiconductor crystal. | ||
| Line 252: | Line 231: | ||
| < | < | ||
| <panel type=" | <panel type=" | ||
| - | < | + | < |
| {{drawio> | {{drawio> | ||
| </ | </ | ||
| Line 266: | Line 245: | ||
| < | < | ||
| - | Doping does **not** mean that the semiconductor becomes strongly charged as a whole. | + | Doping does **not** mean that the semiconductor becomes strongly charged as a whole. |
| - | The crystal is still approximately electrically neutral. | + | The crystal is still approximately electrically neutral. |
| Doping mainly changes how many mobile charge carriers are available. | Doping mainly changes how many mobile charge carriers are available. | ||
| </ | </ | ||
| Line 278: | Line 257: | ||
| <panel type=" | <panel type=" | ||
| < | < | ||
| - | {{: | + | {{drawio>pnjunction.svg}} |
| </ | </ | ||
| </ | </ | ||
| Line 289: | Line 268: | ||
| * a region with almost no mobile charge carriers forms. | * a region with almost no mobile charge carriers forms. | ||
| - | This region is called the **depletion region** or **space-charge region**. | + | < |
| + | The region | ||
| + | This is called the **depletion region** or **space-charge region**. | ||
| + | </ | ||
| < | < | ||
| <panel type=" | <panel type=" | ||
| < | < | ||
| - | {{: | + | {{drawio>evolutionofpnjunction.svg}} |
| </ | </ | ||
| </ | </ | ||
| - | The depletion region behaves like an internal barrier. | + | The depletion region behaves like an internal barrier. |
| Without an external voltage, it prevents a large current. | Without an external voltage, it prevents a large current. | ||
| - | <panel type=" | + | <callout |
| - | The depletion region is like a spring-loaded door. | + | **Mnemonic: PANIC!** |
| - | | + | \[ |
| - | * In the other direction, the spring pushes the door more firmly closed. | + | \begin{align*} |
| + | \text{Positive Anode, Negative Is Cathode} | ||
| + | \end{align*} | ||
| + | \] | ||
| - | The diode behaves similarly: one polarity reduces the barrier, the other polarity increases it. | + | This helps to remember the forward direction of a diode. |
| - | </panel> | + | </callout> |
| ==== Forward and reverse operation ==== | ==== Forward and reverse operation ==== | ||
| Line 321: | Line 306: | ||
| * \(u_{\rm AK}>0\): anode is more positive than cathode. | * \(u_{\rm AK}>0\): anode is more positive than cathode. | ||
| - | * \(u_{\rm AK}<0\): anode is more negative than cathode. | + | * \(u_{\rm AK}<0\): anode is more negative than cathode. |
| + | \\ \\ | ||
| < | < | ||
| ^ Condition ^ Name ^ Effect on depletion region ^ Current ^ | ^ Condition ^ Name ^ Effect on depletion region ^ Current ^ | ||
| - | | \(u_{\rm AK}>0\) | forward bias | depletion region becomes smaller | large current possible | | + | | \(u_{\rm AK}>0\) | forward bias \\ forward voltage is $U_{\rm F} = u_{\rm AK}$ |
| - | | \(u_{\rm AK}<0\) | reverse bias | depletion region becomes larger | only small leakage current, until breakdown | | + | | \(u_{\rm AK}<0\) | reverse bias \\ reverse voltage is $U_{\rm R} = -u_{\rm AK}$ |
| + | </ | ||
| + | \\ | ||
| - | <callout | + | <WRAP> |
| - | **Mnemonic** | + | < |
| + | < | ||
| + | {{drawio> | ||
| + | </ | ||
| + | </ | ||
| - | \[ | ||
| - | \begin{align*} | ||
| - | \text{Positive Anode, Negative Is Cathode} | ||
| - | \end{align*} | ||
| - | \] | ||
| - | This helps to remember | + | <panel type=" |
| - | </callout> | + | Imagine two neighboring tribunes in a stadium (e.g. fan section and main tribune). |
| + | |||
| + | * On the **n-side**, there are many extra people. They represent mobile **electrons**. | ||
| + | * On the **p-side**, there are many empty seats. They represent mobile **holes**. | ||
| + | |||
| + | At first, people near the border can move into empty seats on the other side. \\ | ||
| + | After this happens, there are fewer mobile people and fewer mobile empty seats close to the border. | ||
| + | A locally empty border zone appears. This represents the **depletion region**. | ||
| + | |||
| + | The depletion region is therefore not an extra part inserted between the two sides. | ||
| + | It forms automatically because electrons and holes recombine near the pn junction. | ||
| + | |||
| + | In **forward | ||
| + | The empty border zone becomes narrower, and new people and empty seats are continuously supplied from the outside. A current can flow. | ||
| + | |||
| + | In **reverse bias**, the external voltage pulls people and empty seats away from the border. | ||
| + | The empty border zone becomes wider, so crossing becomes very unlikely. Only a tiny leakage current remains. | ||
| + | </panel> | ||
| ==== Ideal diode model ==== | ==== Ideal diode model ==== | ||
| Line 357: | Line 361: | ||
| \] | \] | ||
| - | < | + | < |
| - | <panel type=" | + | |
| - | < | + | |
| - | {{drawio>block11_ideal_diode_characteristic.svg}} | + | |
| - | </ | + | |
| - | </ | + | |
| <panel type=" | <panel type=" | ||
| Line 403: | Line 402: | ||
| ^ Symbol ^ Meaning ^ | ^ Symbol ^ Meaning ^ | ||
| - | | \(I_{\rm S}(T)\) | reverse saturation current, strongly temperature-dependent | | + | | \(I_{\rm S}(T)\) | reverse saturation current, strongly temperature-dependent |
| - | | \(m\) | emission coefficient, | + | | \(m\) | emission coefficient, |
| - | | \(U_{\rm T}\) | thermal voltage | | + | | \(U_{\rm T}\) | thermal voltage |
| - | | \(k\) | Boltzmann constant | | + | | \(k\) | Boltzmann constant |
| - | | \(e\) | elementary charge | | + | | \(e\) | elementary charge |
| - | | \(T\) | absolute temperature in \({\rm K}\) | | + | | \(T\) | absolute temperature in \({\rm K}\) | |
| + | </ | ||
| + | \\ | ||
| - | At room temperature, | + | Often a **turn-on voltage** $U_{\rm |
| - | + | ||
| - | \[ | + | |
| - | \begin{align*} | + | |
| - | U_{\rm | + | |
| - | \end{align*} | + | |
| - | \] | + | |
| - | + | ||
| - | Typical values | + | |
| < | < | ||
| - | ^ Diode material ^ Approximate threshold voltage \(U_{\rm TO}\) ^ Reverse saturation current \(I_{\rm S}\) ^ | + | ^ Diode material |
| | silicon | \(\approx 0.7~{\rm V}\) | some \({\rm pA}\) | | | silicon | \(\approx 0.7~{\rm V}\) | some \({\rm pA}\) | | ||
| | germanium | \(\approx 0.3~{\rm V}\) | some \(\mu{\rm A}\) | | | germanium | \(\approx 0.3~{\rm V}\) | some \(\mu{\rm A}\) | | ||
| + | </ | ||
| + | |||
| <callout type=" | <callout type=" | ||
| - | The value \(0.7~{\rm V}\) for a silicon diode is not a physical constant. | + | * the turn-on voltage has also some alternative labeling: knee voltage, threshold voltage, diode voltage $U_{\rm D}$, forward voltage $U_{\rm F}$ |
| - | It is a useful approximation for typical currents in small signal and basic power circuits. | + | * The value \(U_{\rm TO} = 0.7~{\rm V}\) for a silicon diode is not a physical constant. |
| + | | ||
| </ | </ | ||
| + | |||
| + | < | ||
| + | {{url> | ||
| + | </ | ||
| ==== Practical diode models for circuit calculation ==== | ==== Practical diode models for circuit calculation ==== | ||
| - | For hand calculations we usually do not use the full exponential equation. | + | For hand calculations we usually do not use the full exponential equation, because it is often too complex for a quick solution. \\ |
| + | Instead the following is often used: | ||
| - | <WRAP> | + | <tabcaption tab_diode_models|Diode models |
| - | <panel type=" | + | |
| - | < | + | |
| - | {{drawio> | + | |
| - | </ | + | |
| - | </WRAP> | + | |
| - | < | + | ^ Model ^ Forward direction ^ Reverse direction ^ Use ^ Example ^ |
| + | | ideal diode | \(u_{\rm AK}=0\) | ||
| + | | constant-voltage model | \(u_{\rm AK}\approx U_{\rm TO}\) | ||
| + | | piecewise-linear model | \(u_{\rm AK}\approx U_{\rm TO}+r_{\rm F}\cdot i_{\rm D}\) | \(i_{\rm D}\approx 0\) | more accurate operating point | How does the diode voltage change when the current changes? | ||
| + | </tabcaption> | ||
| + | \\ | ||
| + | < | ||
| - | ^ Model ^ Forward direction ^ Reverse direction ^ Use ^ | ||
| - | | ideal diode | \(u_{\rm AK}=0\) | \(i_{\rm D}=0\) | switching logic, first estimate | | ||
| - | | constant-voltage model | \(u_{\rm AK}\approx U_{\rm TO}\) | \(i_{\rm D}\approx 0\) | quick current calculations | | ||
| - | | piecewise-linear model | \(u_{\rm AK}\approx U_{\rm TO}+r_{\rm F}i_{\rm D}\) | \(i_{\rm D}\approx 0\) | more accurate operating point | | ||
| The differential forward resistance is | The differential forward resistance is | ||
| Line 486: | Line 484: | ||
| \] | \] | ||
| </ | </ | ||
| - | |||
| - | ==== Operating point with a series resistor ==== | ||
| - | |||
| - | A diode must usually be operated with a current-limiting element. | ||
| - | |||
| - | For the circuit | ||
| - | |||
| - | \[ | ||
| - | \begin{align*} | ||
| - | U_{\rm E} | ||
| - | \rightarrow R | ||
| - | \rightarrow D | ||
| - | \end{align*} | ||
| - | \] | ||
| - | |||
| - | the loop equation is | ||
| - | |||
| - | \[ | ||
| - | \begin{align*} | ||
| - | U_{\rm E} | ||
| - | = | ||
| - | U_R+U_{\rm D}. | ||
| - | \end{align*} | ||
| - | \] | ||
| - | |||
| - | With the constant-voltage model, | ||
| - | |||
| - | \[ | ||
| - | \begin{align*} | ||
| - | U_{\rm D}\approx U_{\rm TO}. | ||
| - | \end{align*} | ||
| - | \] | ||
| - | |||
| - | Therefore | ||
| - | |||
| - | \[ | ||
| - | \begin{align*} | ||
| - | I_{\rm D} | ||
| - | \approx | ||
| - | \frac{U_{\rm E}-U_{\rm TO}}{R}. | ||
| - | \end{align*} | ||
| - | \] | ||
| - | |||
| - | <callout type=" | ||
| - | Never connect a normal diode or LED directly to an ideal voltage source in forward direction. | ||
| - | The diode current must be limited. | ||
| - | </ | ||
| - | |||
| - | ==== Z-diodes and LEDs as diode types ==== | ||
| - | |||
| - | A Z-diode is operated in reverse breakdown. In its operating range, the diode voltage is approximately constant: | ||
| - | |||
| - | \[ | ||
| - | \begin{align*} | ||
| - | u_{\rm Z}\approx U_{\rm Z}. | ||
| - | \end{align*} | ||
| - | \] | ||
| - | |||
| - | The piecewise-linear model is | ||
| - | |||
| - | \[ | ||
| - | \begin{align*} | ||
| - | u_{\rm Z} | ||
| - | \approx | ||
| - | U_{\rm Z}+r_{\rm Z}i_{\rm Z}. | ||
| - | \end{align*} | ||
| - | \] | ||
| - | |||
| - | <panel type=" | ||
| - | Z-diodes are useful for voltage limitation and voltage stabilization. | ||
| - | The practical circuits are treated in [[block12|Block 12]]. | ||
| - | </ | ||
| - | |||
| - | An LED is a diode that emits light in forward direction. The required forward voltage depends on the semiconductor material and therefore on the color. | ||
| - | |||
| - | < | ||
| - | |||
| - | ^ LED color ^ Typical \(U_{\rm TO}\) ^ | ||
| - | | infrared | \(\approx 1.3~{\rm V}\) | | ||
| - | | red | \(\approx 1.6~{\rm V}\) | | ||
| - | | yellow | \(\approx 1.7~{\rm V}\) | | ||
| - | | green | \(\approx 1.8~{\rm V}\) | | ||
| - | | blue | \(\approx 3.2~{\rm V}\) | | ||
| - | |||
| - | <callout type=" | ||
| - | LEDs usually tolerate only small reverse voltages. | ||
| - | Do not operate an LED in reverse direction unless the datasheet explicitly allows it. | ||
| - | </ | ||
| - | |||
| - | ~~PAGEBREAK~~ ~~CLEARFIX~~ | ||
| ===== Exercises ===== | ===== Exercises ===== | ||
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| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | U_{\rm | + | U_{\rm |
| \qquad | \qquad | ||
| R=1.0~{\rm k}\Omega. | R=1.0~{\rm k}\Omega. | ||
| Line 688: | Line 596: | ||
| U_R | U_R | ||
| = | = | ||
| - | U_{\rm | + | U_{\rm |
| = | = | ||
| 5.0~{\rm V}-0.7~{\rm V} | 5.0~{\rm V}-0.7~{\rm V} | ||
| Line 773: | Line 681: | ||
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | U_{\rm | + | U_{\rm |
| \qquad | \qquad | ||
| R=560~\Omega. | R=560~\Omega. | ||
| Line 811: | Line 719: | ||
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | U_{\rm | + | U_{\rm |
| = | = | ||
| RI_{\rm D} | RI_{\rm D} | ||
| Line 823: | Line 731: | ||
| \[ | \[ | ||
| \begin{align*} | \begin{align*} | ||
| - | U_{\rm | + | U_{\rm |
| = | = | ||
| RI_{\rm D} | RI_{\rm D} | ||
| Line 839: | Line 747: | ||
| I_{\rm D} | I_{\rm D} | ||
| = | = | ||
| - | \frac{U_{\rm | + | \frac{U_{\rm |
| \end{align*} | \end{align*} | ||
| \] | \] | ||
| Line 923: | Line 831: | ||
| ===== Embedded resources ===== | ===== Embedded resources ===== | ||
| - | |||
| - | <WRAP group> | ||
| - | <WRAP column half> | ||
| - | <panel type=" | ||
| - | Use this simulation to explore doping and the formation of a diode. | ||
| - | |||
| - | {{url> | ||
| - | </ | ||
| - | </ | ||
| - | |||
| - | <WRAP column half> | ||
| - | <panel type=" | ||
| - | Use this simulation to compare a resistor characteristic with the nonlinear diode characteristic. | ||
| - | |||
| - | {{url> | ||
| - | </ | ||
| - | </ | ||
| - | </ | ||
| ~~PAGEBREAK~~ ~~CLEARFIX~~ | ~~PAGEBREAK~~ ~~CLEARFIX~~ | ||