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| electrical_engineering_and_electronics_2:block13 [2026/06/09 04:38] – mexleadmin | electrical_engineering_and_electronics_2:block13 [2026/06/09 05:22] (current) – mexleadmin |
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| TBD | |
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| - Semiconductor components \\ (approx. 4 blocks, based on previous lectures on [[circuit_design:2_diodes|Diodes]] and [[circuit_design:2_transistors|Transistors]] ) | |
| |
| - Bipolar transistor (structure, designations, characteristic curve, characteristic values) | |
| - Transistor as a switch (circuit, switching times and behavior) | |
| - MOSFET (structure, comparison with bipolar transistor) | |
| - Optional: Transistor as an amplifier | |
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| |
| |
| <callout> A nice introduction to the bipolar transistor can be found in [[http://eng.libretexts.org/Bookshelves/Materials_Science/Supplemental_Modules_(Materials_Science)/Materials_and_Devices/Bipolar_Junction_Transistor|libretexts]]. Some of the following passages, videos and pictures are taken from this introduction. </callout> | <callout> A nice introduction to the bipolar transistor can be found in [[http://eng.libretexts.org/Bookshelves/Materials_Science/Supplemental_Modules_(Materials_Science)/Materials_and_Devices/Bipolar_Junction_Transistor|libretexts]]. Some of the following passages, videos and pictures are taken from this introduction. </callout> |
| |
| This is treated in [[block14|Block 14]]. | This is treated in [[block14|Block 14]]. |
| </callout> | </callout> |
| |
| <WRAP>{{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=CQAgjA7CAMB00OgVnLJA2ALAJnQZjAA5DMjDJsR0xwQlo6BTAWjDACgBzEbYkPbA16F+edDBjsiNYeEyYefMAE5KDTPRKFYYiEjzIweQijiIacC-ARXz7AEqKRYeU-C8JDenU8w07AA8eZRRsTHEDKDDlEAUiEABhQJ4kKPRKXBjcFDiRACF2ABcU8WwIDL4ytVpmbB0ITGh0VTw8ZWUICAI-dF6kZWhsPAgiDvkYsAQQABNGADMAQwBXABtC9gAndxEqnmgd8olJhHYAdzcBIUq+aDO3bAw3FTV2ADdwMEpLj4zDhjxYgw4OI4Aogf5zmwvoILjDbpDPjxDp8Di8gthlKV2vx9jjKLkQABRZIuHZIShEAEPHLgET2AD6BUaALEznQXlU-Dh4HpD3Q9Lw9JwhGU9KQLDA-MIEog9OgvPp-LwyUwyhokpEqvEkBoBIAkskkIQogI6JyhjT4gagqqUJBxPQoJAYgSkkF+hlGlRoAowgCCUzoACsAxJQxCFguUCQKKkJ85ULJWAxSwwinavzk9h6aLlUFOurDhAQuA9LFaSA8sT8-1wL0QAW6y6KwBVZImUpiEARnZtcvxApBEwZDwmE26ivWngeXhCHCKf08BQAPjuglRJSRaOnO3wS6E9YDyWwQxSoRnRv7IinvBHMmUvrC5afr2PzR4LkUMkgV8Sb9CTRIkI0DNlax6YFABihOgkG4goXqAMmEx5sHi04ssgv5tuip4GDsEH8ChAbVlQhAUl2hDDOAfb6gAdgADkshQADoAM4JAAFgsGwLAAxoUjAbAAlixhSCTxyTDOqeAoEaEzGL+CRLBsGyMDRzEsQA4gsgk0axHFcbx-FCSJYnsAA9j4caUOIjQdD4cAiKG7BAA noborder}} | |
| </WRAP> | |
| |
| ==== BJT characteristic curves and differential quantities ==== | ==== BJT characteristic curves and differential quantities ==== |
| * **Control characteristic:** \(I_{\rm C}(I_{\rm B})\) \\ This shows the current gain. | * **Control characteristic:** \(I_{\rm C}(I_{\rm B})\) \\ This shows the current gain. |
| * **Output characteristic:** \(I_{\rm C}(U_{\rm CE})\) for different values of \(I_{\rm B}\). | * **Output characteristic:** \(I_{\rm C}(U_{\rm CE})\) for different values of \(I_{\rm B}\). |
| | |
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| | <WRAP>{{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=DwYwlgTgBAZgvAIgIwHYFQC4GdEAYB0uRuArOmCIkviQGwAsATLQMxIAc79H7qj6IAEaJaSdAAdhCErnQA3CFXQBbbIhIBTALRIxAPgBQUKMADmUAB6JGnKC0a4oN9nZa108BLID0h48AAZAENlcUtrWyR6eidIgE5+WDx0DA1rFiI4uJoWenYWEhl6VnQAO3E8QiIxKFK5SpqAdyDK4hqQAHtW6oRfIxMAJXCEZygomNGkGw9kqEbPWShlIIt66V6-EwthxjiSJ2K7XBQDuJmEenQsMCp2FLSEAGEN-uBtqxGSE+ZGJ1o4v5kJIXK43ZB3TAPABCL38GB2dCcKF+o0YyPOi3EpSUUEEDyQRBUXQQABMNDAggBXAA2GHkeMQWkY+BYKHouH+jBYLCyKBQbHplC8+FoopIcVwXJQHDibPoZz6-mgHymLjRKNwavRwMWimQxFhJkaO1s9kcqM4GMNwGNH1RiMmCStipMcmGul+ZrGUyRiQW6HmiBYHj17JUKzWBHcuLAQRwwsuLpt7p9XtGZudm2TKp96rGNl9mde72scVoTiyRxcGT9iEuUGut3uiAAotaS8g8k4SL8OCxu0DPPXG+DmwgBgB9GFJgDKnXEGmGbhcSFojnFnocVs2-g6UA02OQVwqn2jngsIBqJ50CB3xhMYTWwYbQvY2lQhvvD-3InkQaur7vmgLr+N4HRZt4c4dAuWYdvKSBjLQLjyuWqA1EOoJNpCiAAJLtsMJDsN89hQBuTgFOcw5ghwY54UmcF7GMKDljIJyoGcwJUVhqSIM89EEQkByOGuEz0M+GENtREI8Qg05ZlBC7DAwjiro47AMHYW46re-S7vuh4cVgJ4kFM5wWNwEiMvoun3sAj6zFgQqaEyiZ3v49kIM+jnqNozCfiYYEQQpGiwcMfIIXwUAoIxqCDnWmGjthsltvxHwoOKiHluFiEcRJI40UlACq+EfOwDpuFA6lqjylEJQVMlycWwxlSiBZlcR6HxZJ3EPHRoV2gWNjmkwsTiV1I6MPWMkAGSmBgADc1q2tYmq+t25bqkW-gdowg2sEJfxnuNUljo1207FyA5OINhG1d1iUyX1TV2uwrUIbsEyTXdE1TQ8cgldY-xOFEsTvR+nF1dJDx8f1gP7A4G0oOauC5cdPW4QDIz0CcGTw7QOOat9YJhklgDJhJjjC6EcrX9rjRPowgxWpdYl0ZGq2N2Lo9MPdCKWwwgSG9hV+RsTVEP3fVvXlJS8KPAAFkEEBBCAqQQGAWAYBQmOshFBSkdEYwsBCeUnUljwdKUGAQB01JQPLivK6r6uayA1p7ge6jHuopnAhYV7JHedlQGs0beesSaBQYwDeOAECGEAA noborder}} |
| | </WRAP> |
| | |
| | {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=DwYwlgTgBAZgvAIgIwHYFQC4GdEAYB0uRuATOmCIiYbgBwCs9AzAGwCcJTStKLaUIAEaIWSdAAdhCernQA3CIjFQAttkT0ApgFokYgHwAoKFGABzKAA8lLXFCYk7SW-dbp4CWQHojJ4ACUrGycAFhCoZycSWnc8dAB3DyZ3RQRaWVUAQ0s5JXRBMEycZAQfY1NLIOQWWigSFhII9LqWeliEEPQsMCUYzE1EAGFS3wqqpBI2FsakEKQWtthETqhu3vQMAYQAIRHy4Axx6LqUGZcSU-aM8QA7PKhBLaQidBUAe0QAE00YTIBXAA2GHkj0Qunwyjkgkonj2fmg1gQDhOMwmKKu6FSzxeZT88XGLgcTkJuBWHm8o2A+MRkTqIWJTg4GNxpjkVV0LHsjigHPRS1hUESVBSywyKmyuU8hDID0KxQILBYcNM1LBzi5DI1zMplRpNTqbCm3DsTFI7RWa2QfU2iAAosrgLrlig6vR5rRGiR6GTll0elaNlt-AB9XYsx3jOh1ZoTT20ZL8i3+kgrG0IABkZgwAG4HarkGiLjNjkXtfsnchcJyvUbuNNzX71v1EGGdZH5l75s9q96G6t-dxA4gAJIOitIb11EhdxVTn0dRsIFNDhByMfjOZ1WYRZhb-geJNNtPDcPjpguxyc2ae3BsPuWwfNhCj8MAZRAb3Emiq09qE7srSckw9AyuSCCjH4bxQJodwLqs4hKKQ86WCECYIQgujgeUJh+OIUCSkqqwwkg+BaNoMQsjhph4ZKMpYMROgURBpheG8lJeO+n6aJSbKIryRY8uqJDLvyGRCkuIpLmKEp4IQnThvm-Eplyc5lniVTIsJ4SaZconroifAdigtTsNWtDKAei6Pse9qnlUrRTPUUyGXyln9keWwAKr6cs54REwtRhDMcz3gO1pbC+baImEXYhJyIS7rMd6JlZ4VDD50h6BEfBQCwCURCgGRuQ+Mppp5VEmHAUCnLgKgAGoADRQMOOFVYVgA9wAAghlIEzCg4TMH+KD7r67nIKVWzbLZUUaGwHakLlDR1LgizFQOE0iOk9VNQlXUZQ0djCfQuVzVOfRrUoG0IHltWNXUTB7XZBlMOEnBTIVjkhKBo0lSuti3U1tANfQj2UgAMpkKh4XqoThLSSBMnpT7pKa+ANGw9BsEw2OKugNzoQQxATHjkoEMo8SZLJRPoB+VNEGI4aCFUqEus4gXnDIaljNF3L1C6ISFdGq0-etK5YJkGB-BAEtgG8NwADo3BAmhmLLNwOkz0WiHSJklpzelPcsbDVjlIGOQwoWXSuIB-BgbwwDA2iK8rqty3mBKHfS2WHfQhFgQpHvRn+JLzhS5Y-gtFy1NOr3mZbAZPt5htLtu0QXkwjlsEVIseUM03hzSDDRq9K3RiNcGWvSK6AMmEGW0EBpJQGwtSmuXh4J2VGXN-YzwRMJPcJhdHeTfnfjjtO9i4Kzm5cNnFf+lXT618nmNDeEthXsN8fE0+rYF4grBdreUDME4O9D9ZWwAPK2+IttQIMAAWmTSyAmwQGAWAYBQDpQTBGhdHQm6b6CBLCOFwMoAmWEqLABonEIidMIEOlYkYYAXhwAQCMEAA noborder}} |
| |
| Important parameters around an operating point are | Important parameters around an operating point are |
| \end{align*} | \end{align*} |
| \] | \] |
| |
| |
| <panel type="info" title="Simulation: BJT output characteristics"> | |
| Things to try: | |
| |
| * change the input voltage \(U_{\rm BE}\), | |
| * observe the family of output curves, | |
| * identify cutoff, active region, and saturation. | |
| |
| {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=CQAgjA7CAMB00OgJhE+0AcBWLBmAbAJxK5gYT5T5jghbR0CmAtGGAFADm4+DuSDMLxC4CMGOwBKPQQBZZM8EgzjcIDINoM4WdgA8eKpPhRkGxrCAVkQAYX1LCqE+Fk0LV8CoBC7AC5KRhCmwkjB4jSssDSCCCAAJowAZgCGAK4ANn7sAE4iKGGmYAXhsQjsAO6K-ILCuNAK0JWKSLK1gsQSAG4grPj5DH2opahW2vAocPj947pVQzXVAhIGQkaETmYiyJ42AKIOslBIWDQYBVgK1iqSAPq+q5ioGkoFGGoKrSAAfM1sJaZlMNJg4wNB+idNjZjChriAHuBoO5ToiIZddioAJKg9FIJA0IQQr6fBRdUFuVBgax4SlQOH2Va4Y7g1wFaBOOHYtpqfEqMD0ED4LD9XBYSZWW5g1q3fC3Nz4XCS2BYFgYSWq27QW5IOXa9g9IaFXpCVBfcyocYNcSzZqGr78U2NZoOvEKF2lByUdwQFRECEYGj0g4GIVOYxOL3AjEgACqhyZ4FwKnkpgpnMOFKp-VkNKpHK8dgcpwJlEFOfAEAY1hQMYAOgBnBtNxst2sARwbwWgAFsAGoAGgbmObTY79crgB7gACCRbxFYUeD5EDpSnhwbohHcO2mbMs1cFGj7g-rOennuWeMsRHcQP3+DaR4bJDPIdwn1wTkrYdksNXvB7A4Nhg-ZYGeZAlnI1jCGAnQMBs-IwOgSKTNEiGIDESEcAARlYCZrFYoQCk0Bg-uYpZHG8e6rvWKR+GkOS0QAlgA9gAdrWtasTkjCcCxrHsDhsjUKgsi+kCJzaIchAQqWYphtguwoAAxmkfjMUkSTMBxXE8XxfyhG0LTChIVRCOYGB8nUVrERaJRGFSzyBgWcYGPinzkKgH6oIQVYFrY65kJYyifNAQUeVcDCAMmEDgYCKVqECo9QrjYLkgAlIhgq8GUfAW3gBfi2xQFSNCkL5hnRQYWDpZACi8P0kDJSgCL8PVxRWB5bBUTYzGqQADqpDZKQAFikDFKX4jA5Ix9Z+IxSnsMxdB0G1gh4hgThwOhaEIDE4DsEAA 700,500 noborder}} | |
| </panel> | |
| |
| ~~PAGEBREAK~~ ~~CLEARFIX~~ | ~~PAGEBREAK~~ ~~CLEARFIX~~ |
| |
| ==== BJT operating regions ==== | ==== BJT operating regions ==== |
| |
| A BJT can operate in different regions. | A BJT operates mainly in three different regions. |
| |
| <tabcaption tab_bjt_regions|Basic operating regions of an npn transistor> | <tabcaption tab_bjt_regions|Basic operating regions of an npn transistor> |
| |
| ^ Region ^ Approximate condition ^ Electrical behavior ^ Typical use ^ | ^ Region ^ Approximate condition ^ Electrical behavior ^ Typical use ^ |
| | cutoff | \(I_{\rm B}\approx 0\) | \(I_{\rm C}\approx 0\), transistor blocks | open switch | | | cutoff | \(I_{\rm B}\approx 0\) | \(I_{\rm C}\approx 0\), transistor blocks | open switch | |
| | active region | \(I_{\rm C}\approx B I_{\rm B}\) | collector current controlled by base current | analog amplifier | | | active region | \(I_{\rm C}\approx B I_{\rm B}\) | collector current controlled by base current | analog amplifier | |
| | saturation | \(I_{\rm B}\) large enough, \(U_{\rm CE}\) small | transistor conducts strongly | closed switch | | | saturation | \(I_{\rm B}\) large enough, \\ \(U_{\rm CE}\) small | transistor conducts strongly | closed switch | |
| </tabcaption> | </tabcaption> |
| | \\ |
| | === Switching view === |
| |
| <panel type="info" title="Switching view"> | |
| For a BJT used as a switch: | For a BJT used as a switch: |
| |
| \end{align*} | \end{align*} |
| \] | \] |
| </panel> | |
| |
| The conduction loss of a saturated BJT switch is approximately | The conduction loss of a saturated BJT switch is approximately |
| </callout> | </callout> |
| |
| ==== Switching times of a BJT ==== | === Switching times of a BJT === |
| |
| Real transistor switching is not instantaneous. | Real transistor switching is not instantaneous. |
| | |
| | {{drawio>electrical_engineering_and_electronics_2:switchingdiagram_v01.svg}} |
| |
| Typical time intervals are: | Typical time intervals are: |
| <tabcaption tab_bjt_switching_times|BJT switching times> | <tabcaption tab_bjt_switching_times|BJT switching times> |
| |
| ^ Symbol ^ Meaning ^ | ^ Symbol ^ Meaning ^ |
| | \(t_{\rm d}\) | delay time | | | \(t_{\rm d}\) | delay time | |
| | \(t_{\rm r}\) | rise time | | | \(t_{\rm r}\) | rise time | |
| | \(t_{\rm on}\) | total turn-on time | | | \(t_{\rm on}\) | total turn-on time | |
| | \(t_{\rm s}\) | storage time | | | \(t_{\rm s}\) | storage time | |
| | \(t_{\rm f}\) | fall time | | | \(t_{\rm f}\) | fall time | |
| | \(t_{\rm off}\) | total turn-off time | | | \(t_{\rm off}\) | total turn-off time | |
| </tabcaption> | </tabcaption> |
| | \\ |
| During switching, both current and voltage can be significant at the same time. | During switching, both current and voltage can be significant at the same time. \\ |
| Therefore switching losses occur during turn-on and turn-off. | Therefore switching losses occur during turn-on and turn-off. |
| |
| \[ | \[ |
| \begin{align*} | \begin{align*} |
| p(t)=u_{\rm CE}(t)i_{\rm C}(t). | p(t)=u_{\rm CE}(t) \cdot i_{\rm C}(t). |
| \end{align*} | \end{align*} |
| \] | \] |
| This contributes to the storage time \(t_{\rm s}\). | This contributes to the storage time \(t_{\rm s}\). |
| </panel> | </panel> |
| |
| ==== Short preview: transistor switch and PWM ==== | |
| |
| A transistor switch can connect and disconnect a load very quickly. | |
| If the switch is periodically on and off, the load sees an average voltage. | |
| |
| For an ideal switch with supply voltage \(U_{\rm dc}\): | |
| |
| \[ | |
| \begin{align*} | |
| \overline{u}_{\rm L} | |
| = | |
| \frac{1}{T}\int_0^T u_{\rm L}(t)\,{\rm d}t | |
| = | |
| \frac{T_{\rm on}}{T}U_{\rm dc}. | |
| \end{align*} | |
| \] | |
| |
| The duty cycle is | |
| |
| \[ | |
| \begin{align*} | |
| d=\frac{T_{\rm on}}{T}. | |
| \end{align*} | |
| \] | |
| |
| Thus | |
| |
| \[ | |
| \begin{align*} | |
| \boxed{ | |
| \overline{u}_{\rm L}=dU_{\rm dc} | |
| } | |
| \end{align*} | |
| \] | |
| |
| <callout> | |
| This is the basic idea of pulse-width modulation (PWM). | |
| Applications to motor drivers and power stages are continued in [[block14|Block 14]]. | |
| </callout> | |
| |
| ~~PAGEBREAK~~ ~~CLEARFIX~~ | ~~PAGEBREAK~~ ~~CLEARFIX~~ |
| </panel> | </panel> |
| </WRAP> | </WRAP> |
| |
| <panel type="info" title="Simulation: MOSFET as voltage-controlled switch"> | |
| Things to try: | |
| |
| * change the gate voltage, | |
| * observe that the gate draws no stationary current, | |
| * observe how the drain-source path changes from blocking to conducting. | |
| |
| {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=CQAgjA7CAMB00OgJhE+0AcBWLBmAbAJxK5gYT5T5jghbR0CmAtGGAFADm4+DuSDMLxC4CMGOwBKPQQBZZM8EgzjcIDAzhq4KTbCzsAHuAhqkecNlRZ8IBWRAARI+CHX7uBuaj2VAcXYAJxEUJAgUNlDw8TBEdgB3RX5BYU8FaATFJFkUwWIJADcQkL4o3VQ7QVodJHwMYg0wrGJ8ZSwYfUz+EqSBCWNIBTTLW08fSxAAZUzI1GiwZTndFzAsBSQkGiFbDYV1hQKV2RpN+wtN8YdnAdwoAVswWVDoQjsJgEl2Mi3hR-tf-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-WnZi-knPZITsQhI2QWQc3jPMvXMOqwTTZgckjZNluRFhjhzPN6HDQtjDfKzQ3UdjXjNFwDIAkB8HaZgl3ZSQXEoawUG4m9iICED9lsE7skuiYXvvE7WDWEQIF01Y2Q+T8IBG2RRgwDTHlNCZrjobjmA2O7wSs8TjItGxXnMmgAN0xZ2S5IA 700,500 noborder}} | |
| </panel> | |
| |
| ==== MOSFET structure and channel formation ==== | ==== MOSFET structure and channel formation ==== |
| \(U_{\rm GS(th)}\) is **not** the voltage for a fully switched-on MOSFET. | \(U_{\rm GS(th)}\) is **not** the voltage for a fully switched-on MOSFET. |
| |
| For low conduction loss, use the gate voltage at which the datasheet specifies | For low conduction loss, use the gate voltage at which the datasheet specifies $R_{\rm DS(on)}$. |
| | |
| \[ | |
| \begin{align*} | |
| R_{\rm DS(on)}. | |
| \end{align*} | |
| \] | |
| </panel> | </panel> |
| </WRAP> | </WRAP> |
| |
| ~~PAGEBREAK~~ ~~CLEARFIX~~ | ~~PAGEBREAK~~ ~~CLEARFIX~~ |
| |
| ==== MOSFET output characteristics ==== | ==== MOSFET output characteristics ==== |
| |
| The drain current \(I_{\rm D}\) depends on | The drain current $I_{\rm D}$ depends on |
| | * the drain-source voltage $U_{\rm DS}$, and |
| | * the gate-source voltage $U_{\rm GS}$. |
| |
| * the drain-source voltage \(U_{\rm DS}\), | {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=CQAgjCAMB0lwTFa8CscCcAWOYDMA2feMedEfSEFETXKgUwFowwAoAM3E0xFwA4eYAOz5eA3ojDRqMSPFYAncCTGCVuAlHBxIrAObgRNXJKPc+W3WD4Rhok5Tu8UiR-AyVcTIUhy-IELIBrABuNBb8PJgRmpSI7kiBltKsAEqG9glO8HwWniB8juDJKKwA7sqIkVw81bph0caIjXUgzZSy1FJ5SKUVTrTNFoNQ5RlN49gdYyxVmi2xM0a4LuMEeazYdPBC8bvkkMP4PB0A+senkKeYYESnKEy3p2CPQpen8O+4rAAeBXQ3Sjoag3AHgCwAVV+IHQPkwWXgAMRNHBIAA4gBlaEkZq3Li4shRSiAZMJoShcD4cj58EJtuhKIJIQAdADOrPZbLZAEd2QAHMDAyCsgC2ADUyZgyKQeCghNRSHDUZiyXwyLhrOQhBATBBGSAmfz6UKWWKVREbprPNwURqDdY0CLxX8ULleBRLW6wbb+YVjabnTYxNQUOg6Pxhqioc70FVQ+RhLx0KI9QARLF-eFxIQM1BtWk2iwASWh8J4O0JmhyzVRWIARjRjm0Y1Q+NQCDJodUTADsLwLYJECyAIYAFwArgpRwBLAD2ADt2Uy5wp6HpZ3OSyhtUIyC4fPxqyoAMJjkesmfsdis1Kr9fYvj2OPuR-Jmgk6HENXoCDwa24LAFiAaYfnIYjxGAtStoBUYgMwZaYPuKDymgKK-iAc6MEeAAWQ5znO9AADasvQc44XOADG9DCiRZ4sgAsgA8hiABiACiAAqrBAA 700,500 noborder}} |
| * the gate-source voltage \(U_{\rm GS}\). | |
| |
| <WRAP> | \\ |
| <panel type="default"> | |
| <imgcaption fig_mosfet_output_characteristic|Qualitative output characteristics of an n-channel enhancement MOSFET.></imgcaption> | |
| {{drawio>block13_mosfet_output_characteristics.svg}} | |
| </panel> | |
| </WRAP> | |
| |
| A MOSFET has several operating regions. Their names can be confusing because they are not identical to the BJT names. | <WRAP><imgcaption picP|Function of the MOSFET> |
| | {{elektronische_schaltungstechnik:mosfet-front-final-test_jpg_project-body.jpg?400}} |
| | </imgcaption></WRAP> |
| | |
| | A MOSFET has several operating regions. \\ |
| | Their names can be confusing because they are not identical to the BJT names. |
| |
| <tabcaption tab_mosfet_regions|Basic regions of an n-channel enhancement MOSFET> | <tabcaption tab_mosfet_regions|Basic regions of an n-channel enhancement MOSFET> |
| |
| ^ Region ^ Approximate condition ^ Electrical behavior ^ Typical use ^ | ^ Region ^ Approximate condition ^ Electrical behavior ^ Typical use ^ |
| | cutoff | \(U_{\rm GS}<U_{\rm GS(th)}\) | no useful channel, \(I_{\rm D}\approx 0\) | open switch | | | cutoff | \(U_{\rm GS}<U_{\rm GS(th)}\) | no useful channel, \(I_{\rm D}\approx 0\) | open switch | |
| | linear / ohmic region | \(U_{\rm GS}\) high, \(U_{\rm DS}\) small | behaves like a controlled resistor | closed switch | | | linear / ohmic region | \(U_{\rm GS}\) high, \(U_{\rm DS}\) small | behaves like a controlled resistor | closed switch | |
| | MOSFET saturation region | \(U_{\rm GS}\) high, \(U_{\rm DS}\) larger | current mainly controlled by \(U_{\rm GS}\) | analog operation, current-source-like behavior | | | MOSFET saturation region | \(U_{\rm GS}\) high, \(U_{\rm DS}\) larger | current mainly controlled by \(U_{\rm GS}\) | analog operation, current-source-like behavior | |
| </tabcaption> | </tabcaption> |
| | \\ |
| <callout type="warning" icon="true"> | <callout type="warning" icon="true"> |
| The word **saturation** means different things for BJTs and MOSFETs. | The word **saturation** means different things for BJTs and MOSFETs. |
| \[ | \[ |
| \begin{align*} | \begin{align*} |
| U_{\rm DS}\approx R_{\rm DS(on)}I_{\rm D}. | U_{\rm DS}\approx R_{\rm DS(on)} \cdot I_{\rm D}. |
| \end{align*} | \end{align*} |
| \] | \] |
| P_{\rm on,MOS} | P_{\rm on,MOS} |
| = | = |
| R_{\rm DS(on)}I_{\rm D}^2 | R_{\rm DS(on)} \cdot I_{\rm D}^2 |
| } | } |
| \end{align*} | \end{align*} |
| \] | \] |
| |
| <callout type="info" icon="true"> | |
| **Unit check** | |
| |
| \[ | |
| \begin{align*} | |
| [P_{\rm on,MOS}] | |
| = | |
| \Omega\cdot{\rm A}^2 | |
| = | |
| \frac{{\rm V}}{{\rm A}}\cdot{\rm A}^2 | |
| = | |
| {\rm V\,A} | |
| = | |
| {\rm W}. | |
| \end{align*} | |
| </callout> | |
| |
| <panel type="info" title="Simulation: MOSFET output characteristics"> | |
| Things to try: | |
| |
| * change \(U_{\rm GS}\), | |
| * observe the family of output curves, | |
| * identify cutoff, linear/ohmic region, and MOSFET saturation region. | |
| |
| {{url>https://www.falstad.com/circuit/circuitjs.html?running=false&ctz=CQAgjCAMB0lwTFa8CscCcAWOYDMA2feMedEfSEFETXKgUwFowwAoAM3E0xFwA4eYAOz5eA3ojDRqMSPFYAncCTGCVuAlHBxIrAObgRNXJKPc+W3WD4Rhok5Tu8UiR-AyVcTIUhy-IELIBrABuNBb8PJgRmpSI7kiBltKsAEqG9glO8HwWniB8juDJKKwA7sqIkVw81bph0caIjXUgzZSy1FJ5SKUVTrTNFoNQ5RlN49gdYyxVmi2xM0a4LuMEeazYdPBC8bvkkMP4PB0A+senkKeYYESnKEy3p2CPQpen8O+4rAAeBXQ3Sjoag3AHgCwAVV+IHQPkwWXgAMRNHBIAA4gBlaEkZq3Li4shRSiAZMJoShcD4cj58EJtuhKIJIQAdADOrPZbLZAEd2QAHMDAyCsgC2ADUyZgyKQeCghNRSHDUZiyXwyLhrOQhBATBBGSAmfz6UKWWKVREbprPNwURqDdY0CLxX8ULleBRLW6wbb+YVjabnTYxNQUOg6Pxhqioc70FVQ+RhLx0KI9QARLF-eFxIQM1BtWk2iwASWh8J4O0JmhyzVRWIARjRjm0Y1Q+NQCDJodUTADsLwLYJECyAIYAFwArgpRwBLAD2ADt2Uy5wp6HpZ3OSyhtUIyC4fPxqyoAMJjkesmfsdis1Kr9fYvj2OPuR-Jmgk6HENXoCDwa24LAFiAaYfnIYjxGAtStoBUYgMwZaYPuKDymgKK-iAc6MEeAAWQ5znO9AADasvQc44XOADG9DCiRZ4sgAsgA8hiABiACiAAqrBAA 700,500 noborder}} | |
| </panel> | |
| |
| ==== MOSFET types ==== | ==== MOSFET types ==== |
| <tabcaption tab_mosfet_types|Basic MOSFET types> | <tabcaption tab_mosfet_types|Basic MOSFET types> |
| |
| ^ Channel type ^ Enhancement type / self-blocking ^ Depletion type / self-conducting ^ | ^ Channel type ^ Enhancement type / self-blocking ^ Depletion type / self-conducting ^ |
| | n-channel | off at \(U_{\rm GS}=0\), on for sufficiently positive \(U_{\rm GS}\) | on at \(U_{\rm GS}=0\), can be reduced by negative \(U_{\rm GS}\) | | | n-channel | off at \(U_{\rm GS}=0\), on for sufficiently positive \(U_{\rm GS}\) | on at \(U_{\rm GS}=0\), can be reduced by negative \(U_{\rm GS}\) | |
| | p-channel | off at \(U_{\rm GS}=0\), on for sufficiently negative \(U_{\rm GS}\) | on at \(U_{\rm GS}=0\), can be reduced by positive \(U_{\rm GS}\) | | | p-channel | off at \(U_{\rm GS}=0\), on for sufficiently negative \(U_{\rm GS}\) | on at \(U_{\rm GS}=0\), can be reduced by positive \(U_{\rm GS}\) | |
| </tabcaption> | </tabcaption> |
| | \\ |
| In many mechatronic power circuits, the most common device is the **n-channel enhancement MOSFET**. | In many mechatronic power circuits, the most common device is the **n-channel enhancement MOSFET**. |
| |
| <tabcaption tab_bjt_mosfet_comparison|BJT and MOSFET as switching elements> | <tabcaption tab_bjt_mosfet_comparison|BJT and MOSFET as switching elements> |
| |
| ^ Property ^ BJT ^ MOSFET ^ | ^ Property ^ BJT ^ MOSFET ^ |
| | control quantity | base current \(I_{\rm B}\) | gate-source voltage \(U_{\rm GS}\) | | | control quantity | base current \(I_{\rm B}\) | gate-source voltage \(U_{\rm GS}\) | |
| | stationary control current | required | approximately zero | | | stationary control current | required | approximately zero | |
| | stationary control loss | \(P_{\rm ctrl}\approx U_{\rm BE}I_{\rm B}\) | very small, but gate must be charged and discharged during switching | | | stationary control loss | \(P_{\rm ctrl}\approx U_{\rm BE}I_{\rm B}\) | very small, but gate must be charged and discharged during switching | |
| | on-state loss | \(P_{\rm on}\approx U_{\rm CE,sat}I_{\rm C}\) | \(P_{\rm on}=R_{\rm DS(on)}I_{\rm D}^2\) | | | on-state loss | \(P_{\rm on}\approx U_{\rm CE,sat}I_{\rm C}\) | \(P_{\rm on}=R_{\rm DS(on)}I_{\rm D}^2\) | |
| | switching behavior | storage charge can slow turn-off | often faster, but gate capacitance matters | | | switching behavior | storage charge can slow turn-off | often faster, but gate capacitance matters | |
| | typical risk | current gain \(B\) varies strongly | gate oxide sensitive to overvoltage and ESD | | | typical risk | current gain \(B\) varies strongly | gate oxide sensitive to overvoltage and ESD | |
| </tabcaption> | </tabcaption> |
| |
| <callout type="warning" icon="true"> | <callout type="warning" icon="true"> |
| MOSFET gates are sensitive. | MOSFET gates are sensitive. |
| A too large \(|U_{\rm GS}|\) can destroy the thin gate oxide. | A too large \(|U_{\rm GS}|\) can destroy the thin gate oxide. \\ |
| </callout> | </callout> |
| |