| Electronics > Projects, Designs, and Technical Stuff |
| Convert 0..5v PWM to 6,5..11,5v |
| << < (3/8) > >> |
| ogden:
--- Quote from: wraper on December 27, 2018, 05:31:03 pm ---Sallen-key with needed gain will have less parts and offer better signal filtering than this + RC. --- End quote --- Cost is an issue here two BJT's are much cheaper than opamp. OP says that response time does not matter, so opamp-based filter have no advantages here compared to simple RC filter. |
| wraper:
--- Quote from: ogden on December 27, 2018, 05:51:34 pm --- --- Quote from: wraper on December 27, 2018, 05:31:03 pm ---Sallen-key with needed gain will have less parts and offer better signal filtering than this + RC. --- End quote --- Cost is an issue here two BJT's are much cheaper than opamp. OP says that response time does not matter, so opamp-based filter have no advantages here compared to simple RC filter. --- End quote --- Cheaper than what, 10-30 cents for opamp? It has advantage of being second order filter and having buffered output, thus not depending on input resistance of what it drives. |
| ogden:
--- Quote from: wraper on December 27, 2018, 05:57:37 pm ---Cheaper than what, 10-30 cents for opamp? It has advantage of being second order filter and having buffered output, thus not depending on input resistance of what it drives. --- End quote --- Does < 3 cents/piece (qty 100) of MMBT3904 qualify? For slow application you can use just single transistor shifter as well. Yes, buffer of opamp is good "nice to have" feature. I am not against opamp-based filter, I just say that plain RC filter is most widely used, thus shall be offered first. |
| SiliconWizard:
Something like the following (example with a 10kHz PWM signal). The two LP stages get you a decent filtering. The plus is you keep your whole PWM dynamic range. Corollary is it will output ~6.5V even when the PWM signal is not running, which won't be the case with solutions which are just scaling without shifting. |
| Benta:
I'd do it like this: (quick and dirty sketch, sorry) You might even skip the first filter. It's the perfect application for my favorite R-R opamp, LMC6482 (no affiliation). |
| Navigation |
| Message Index |
| Next page |
| Previous page |