Timeline for Why do not we use always current signal sources for BJT amplifiers?
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Jun 28, 2020 at 18:00 | history | tweeted | twitter.com/StackElectronix/status/1277300757168099329 | ||
| Jun 28, 2020 at 14:38 | answer | added | Circuit fantasist | timeline score: 3 | |
| Jun 28, 2020 at 12:28 | comment | added | Horror Vacui | You might check this answer: electronics.stackexchange.com/a/497821/152483 . Although it is about MOS transistor, the principle is the same: smaller sensitivity. | |
| Jun 28, 2020 at 12:09 | history | became hot network question | |||
| Jun 28, 2020 at 11:12 | answer | added | analogsystemsrf | timeline score: 1 | |
| Jun 28, 2020 at 10:50 | vote | accept | Kinka-Byo | ||
| Jun 28, 2020 at 9:21 | answer | added | Daniele Tampieri | timeline score: 6 | |
| Jun 28, 2020 at 7:56 | comment | added | Andy aka | (1) Most signal sources are voltage (2) converting a voltage source is complicated (3) running BJTs at maximum beta produces totally undesirable temperature/Beta problems (4) running with an emitter resistor solves this. | |
| Jun 28, 2020 at 5:43 | answer | added | Neil_UK | timeline score: 4 | |
| Jun 28, 2020 at 4:28 | comment | added | jonk | Because \$\beta\$ isn't predictable. It varies from device to device within a family, varies over operating temperature, varies with respect to collector current (though more so at the extremes, I admit), drifts over time, etc. Better to operate it as an emitter follower (they call it emitter degeneration but it's really also just operating it as an emitter follower) that creates a nice, clean, predictable linear current vs input voltage. | |
| Jun 28, 2020 at 4:22 | comment | added | D.A.S. | To resolve this issue, we add an emitter resistor to keep DC base current constant and then use the AC emitter voltage to modulate the AC current with less gain (=Rc/Re) but more linearity, or we use negative feedback which lowers impedance and less voltage gain (~70% Rf/Rin) but gives the best linearity. | |
| Jun 28, 2020 at 4:06 | history | asked | Kinka-Byo | CC BY-SA 4.0 |