| Electronics > Projects, Designs, and Technical Stuff |
| 0.13x vs 1.0x gain op amp regulated power supply - fail |
| << < (4/8) > >> |
| HendriXML:
--- Quote from: xavier60 on February 14, 2019, 01:59:46 am ---An op-amp configured as a non-inverting amplifier with a feedback capacitor from the op-amp's output to inverting input will give the same result plus even more gain at DC. This will reduce the regulators steady state output voltage error to less than a millivolt if the layout is done right. BTW, your output stage is current sourcing into a capacitor. For the feedback loop to be stable in this situation, the error amplifier(op-amp) needs to have some proportional gain. An op-amp configured as mentioned above has a gain that can only drop to one at higher frequency. This is well suited. --- End quote --- I think I understand most of what you say, but just to be sure I made a schematic. Will also use that to think things through and see the benefits. Losing the positive feedback is probably one of them. The change has some "double inversion" (low band -> highband, positive fb -> negative fb) to it, so it will probably change some characteristics too. |
| HendriXML:
Looking at the schematics I think you mean loosing the diff-amp stuff too, like so. |
| HendriXML:
--- Quote from: HendriXML on February 13, 2019, 09:04:50 pm ---To my understanding such a low gain in the first stage can only work if there’s some offset or voltage lift towards the Mosfet gate. Any idea how this normally is implemented/controlled? --- End quote --- I think the proposed schematics answers that question. Saves a lot of resistors :-+. |
| xavier60:
A balanced input amplifier would be useful possibly for sensing voltage at the output terminals. I haven't given it much thought though and I have never been able to justify the need in the power supplies that I have built. |
| HendriXML:
One difference in the proposed schematic is that the capacitor is now sourced via R5. So a sudden increase in the supply voltage, might pull on the gate wouldn’t it? A phenomenon which has to be regulated, and might have effects on the output. |
| Navigation |
| Message Index |
| Next page |
| Previous page |