Timeline for Driving a difficult load with an Op-Amp: high capacitance, high current, high speed
Current License: CC BY-SA 4.0
12 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| Aug 15, 2018 at 11:46 | comment | added | jalalipop | This didn't quite fix the oscillation on its own, but this plus a series 50 ohm resistor (which I needed anyway) after the feedback point did it for me. The resistor alone wasn't enough. Thanks! | |
| Aug 15, 2018 at 11:45 | vote | accept | jalalipop | ||
| Aug 14, 2018 at 12:59 | comment | added | John Birckhead | I was trying to suggest adding this stage after the op amp and using the same strategy as on your design (feedback from the output). | |
| Aug 14, 2018 at 11:34 | comment | added | jalalipop | @JohnBirckhead I had tried that but the amplitude accuracy isn't great because of the mismatch between the diode Vf and the BJT VBE, especially with all the current sunk by the transistors. | |
| Aug 13, 2018 at 20:49 | comment | added | John Birckhead | You can try avoiding discontinuity in the manner described in electronics.stackexchange.com/questions/264084/… | |
| Aug 13, 2018 at 20:46 | history | edited | John Birckhead | CC BY-SA 4.0 |
added 4 characters in body
|
| Aug 13, 2018 at 20:45 | comment | added | John Birckhead | I should have said "two transistors" not "two op amps." I will edit. | |
| Aug 13, 2018 at 19:51 | comment | added | jalalipop | Ah yes I see that you mentioned that in your answer... I'd think there's a concern of both BJTs being on simultaneously with two independent op-amps driving the two. I'll simulate and look for this. | |
| Aug 13, 2018 at 19:46 | comment | added | Jonathan S. | @jalalipop No, because that would have a "dead zone" where neither of the transistors are on due to the base-emitter voltage drop. And you might want to use RF transistors with ~1GHz transition frequency. The 2N2907 and ZXTP25100 (ft=200MHz) will only provide a gain of about 4 (200MHz/50MHz) at those frequencies, possibly ruining your rise and fall time. | |
| Aug 13, 2018 at 19:12 | comment | added | jalalipop | One question, why do I need two op-amps? Would it not be acceptable to have one op amp with a PNP and NPN follower in your standard push-pull configuration like this: en.wikipedia.org/wiki/Push%E2%80%93pull_output#/media/… | |
| Aug 13, 2018 at 19:08 | comment | added | jalalipop | Holy crap. After a quick scan I think you're right. I will try adding a "push" circuit and post my results. | |
| Aug 13, 2018 at 19:04 | history | answered | John Birckhead | CC BY-SA 4.0 |
.png){kind=link}