Timeline for Differential Amplifier's Unusual Behavior
Current License: CC BY-SA 3.0
26 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Feb 27, 2018 at 1:17 | history | tweeted | twitter.com/StackElectronix/status/968294099362242561 | ||
| Feb 26, 2018 at 21:00 | history | reopened |
lucenzo97 Bence Kaulics Dave Tweed |
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| Feb 26, 2018 at 18:34 | review | Reopen votes | |||
| Feb 26, 2018 at 21:00 | |||||
| Feb 26, 2018 at 12:28 | history | closed |
Andy aka Voltage Spike♦ Finbarr user105652 Daniel Grillo |
Needs details or clarity | |
| Feb 23, 2018 at 4:05 | comment | added | user105652 | Why is C1 present when you have a bipolar power supply and Q1 is referenced to ground? | |
| Feb 22, 2018 at 18:17 | vote | accept | lucenzo97 | ||
| Feb 22, 2018 at 18:17 | vote | accept | lucenzo97 | ||
| Feb 22, 2018 at 18:17 | |||||
| Feb 21, 2018 at 16:37 | comment | added | lucenzo97 | @G36 Okay. So, isn't said that 90° of phase margin would be perfect value for stability? And as we approach closed-loop gain of unity we also approach 90° of phase margin? | |
| Feb 21, 2018 at 16:24 | comment | added | G36 | The small the closed loop gain is the more prone to the oscillation the circuit will be. electronics.stackexchange.com/questions/45064/… read Lvw post. And haven't we already discussed this? When you build the amplifier based on my schematic with unity gain, the circuit oscillates like hell. But increasing the gain to 11 stop the oscillations. Do you remember this? | |
| Feb 21, 2018 at 12:26 | answer | added | Andy aka | timeline score: 2 | |
| Feb 21, 2018 at 4:47 | answer | added | τεκ | timeline score: 2 | |
| Feb 21, 2018 at 0:44 | answer | added | jonk | timeline score: 3 | |
| Feb 20, 2018 at 22:43 | answer | added | Daniele Tampieri | timeline score: 7 | |
| Feb 20, 2018 at 22:09 | comment | added | jonk | @Keno Please work out and compute what you get for the voltage at the junction of \$R_1\$ and \$R_2\$. What is the Thevenin voltage there and what is the Thevenin resistance there? Provide your equations and approach. Then examine your \$Q_3\$ and \$R_{E_3}\$ design and tell me what you think this should be doing. Not what it is doing. But what, in theory, it should do. | |
| Feb 20, 2018 at 22:00 | comment | added | lucas92 | Did you try to simulate the circuit in LTSpice? Anyway, you should look at the way you make the current bias for Q1 and Q2 : I expect a current mirror feeding the circuit but all I see is a transistor polarized with a voltage divider. The rest looks pretty much standard to me (i.e. the feedback network going through the comparator). | |
| Feb 20, 2018 at 21:37 | review | Close votes | |||
| Feb 26, 2018 at 12:28 | |||||
| Feb 20, 2018 at 21:25 | comment | added | lucenzo97 | @AlmostDone Okay, with that being said, I still doubt that any things regarding to small signal or AC is going to be different than as it is now (the problems that I have described)... | |
| Feb 20, 2018 at 21:22 | comment | added | lucenzo97 | @Andyaka Thank you for your notice; I have just edited it. | |
| Feb 20, 2018 at 21:22 | history | edited | lucenzo97 | CC BY-SA 3.0 |
added 63 characters in body
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| Feb 20, 2018 at 21:18 | comment | added | Andy aka | Loop gain is what it is, what you are referring to is the closed loop gain. Please fix. | |
| Feb 20, 2018 at 21:07 | comment | added | AlmostDone | Edit: ...the -V supply. | |
| Feb 20, 2018 at 21:07 | comment | added | AlmostDone | I believe Q3 is not fully biased. Calculate the drop you need across RE3 for 2 mA, add ~.6 V to that, and that's what you need between Q3 base and the V supply. | |
| Feb 20, 2018 at 20:54 | comment | added | lucenzo97 | @AlmostDone Litle bit less - around 1.5 mA; I don't know why exactly but currents are split equally between two collectors of Q1 and Q2. | |
| Feb 20, 2018 at 20:27 | comment | added | AlmostDone | I'm looking at the D.C. conditions. Have you measured the voltage across RE3 to verify your diff pair has 2 mA flowing? | |
| Feb 20, 2018 at 20:09 | history | edited | Neil_UK | CC BY-SA 3.0 |
fixed up your broken link
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| Feb 20, 2018 at 19:51 | history | asked | lucenzo97 | CC BY-SA 3.0 |