Timeline for What is the purpose of this bias resistor?
Current License: CC BY-SA 3.0
5 events
| when toggle format | what | by | license | comment | |
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| Aug 31, 2019 at 11:54 | comment | added | jose.angel.jimenez | The purpose of D2 is protecting Q1 so that the maximum Vgs rating is respected. For Q1, Vgs must be between -20V and +20V. | |
| Jun 24, 2016 at 20:51 | comment | added | Jim Fischer | Agreed. To test how Q2's worst case IDSS affects the PSpice circuit simulation, one could set VIN=60VDC, replace Q2 with a 50 uADC current source (IDC), and then run, say, a Bias Point simulation to estimate steady-state Q1 VGS for the three cases mentioned above (or perhaps run a DC sweep of the IDC source). One could additionally assign tolerances to the passive components and run a DC Sweep of VIN in conjunction with a Monte Carlo or Worst Case simulation, and include a Smoke analysis to gain additional insight. These tasks are left as an exercise for the reader. | |
| Jun 24, 2016 at 14:22 | comment | added | Spehro 'speff' Pefhany | +1 It should be noted that SPICE simulation models will use 'typical' values for things like leakage as a function of temperature. Worst-case values should be used for design purposes- SPICE is more-or-less the equivalent of building a circuit to see if one instantiation happens to work. In reality some parts will be worse or better than others, and the parts are only guaranteed to do what is on the datasheet. | |
| Jun 24, 2016 at 5:35 | history | edited | Jim Fischer | CC BY-SA 3.0 |
added 10 characters in body
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| Jun 24, 2016 at 5:29 | history | answered | Jim Fischer | CC BY-SA 3.0 |