0
\$\begingroup\$

I have a staircase generator circuit with a Mosfet connected to capacitor 2. The input of the capacitor is connected to a comparator and I wish for the Mosfet to cutoff when the output of the comparator is high. The comparator is connected to a sine wave generator enter image description here The waveform I want to achieve is shown below. enter image description here I am having problems achieving this, when the Mosfet is disconnected as above, the wave form I get is this. enter image description here So the blue staircase wave is working as intended albeit no resetting. However the moment I connect it the staircase waveform is affected with some weird fluttering at the beginning and then it not resetting the staircase anyway enter image description here. I have confirmed that with a manual switch the staircase resets as needed however I cannot get the transistor to work as intended.

enter image description here

\$\endgroup\$
  • 1
    \$\begingroup\$ This question looks extremely familiar... You didn't happen to delete this question and ask it again, did you? \$\endgroup\$ – KingDuken Apr 25 '18 at 15:17
  • \$\begingroup\$ I deleted it yesterday because I realised I misunderstood the question, and what I was asking for was not possible or at more difficult than the scope of the question. Unfortunately only realised after wasting a lot of time. \$\endgroup\$ – Intent Filters Apr 25 '18 at 16:20
0
\$\begingroup\$

It cannot work like that. The mofet discharges the capacitor just down to the value where VStaircase goes a bit lower than Vsine, not down to zero as you wish. It's a negative feedback, that it should do.

To act as you wish you need to trigger a short impulse that fully opens the mosfet for a short time.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.