Negative supply from oscilator

[DarkZero]

hello all!

Recently i needed a negative power supply  so my "lab power supply" can go to 0V, so i built a sine oscillator out of 2 op-amp's decoupled it with a capacitor and rectified the negative part with a diode but i got strange results both in simulation and on scope so i googled some internet schematics and found out that there should be a diode rectifying the positive part to ground after decoupling cap. usually when do this with transformer works fine without that diode.

so yes my question is a newbie one but whats the purpose of that diode if someone can explain.

thx in advance

 

[PA0PBZ]

Without the diode to ground the capacitor will charge to 5 (- 0.7 diode drop)  volt so that at the left side of the cap you will end up with a sinus from 0 to 10 volt, and there's no way to make a negative voltage from that. You can measure that by probing the point where the diode to ground should be, see the attachment. Also, you should have a load and another cap at the left.

[Bored@Work]

For more details, Dave made a video about this. Sorry, don't remember the title.

[Alana]

I think its this one http://www.eevblog.com/2013/05/10/eevblog-469-cockcroft-walton-multiplier/

[DarkZero]

thx for all replies ill go check that video maybe ill get it how it works