+/- supply frm single chip

why sir???dnt we hv any chip for this ??

What you apparently want is to go from 20V (whether AC or DC has not been specified] to 3 outputs:

Assuming it's 20Vdc in, there may be triple supply switchers out there that can do buck and invert in the same device, but I personally don't know of any (and I don't feel ike looking through catalogues on Sunday either).

Alternatively, you would be looking for a dual linear with a switched cap inverter (not a particularly good choice for precision electronics, incidentally), and once more I don't know of any.

Given that using switchers will necesssarily increase your component count by a minimum of two inductors, you would be better off using 3 devices with the associated input and output caps (which you will need with any supply).

If your input is AC, you'll need a rectifier in front of it as well (as all the others here could tell you).

Txltn: Wht u apprntly wnt is 2 go frm 20V (whthr AC or DC hs nt bn spcfd] 2 3 otpts:

Assmn it's 20Vdc in, thr my be trpl spply swtchrs avlbl that cn do bck and nvrt in th sm dvc, but I prsnlly dnt knw of ny (nd I dnt fl lk lkng thru catlgs on Sndy ethr).

Altrntivly, u wld be lkng 4 a dl lnr with a swtchd cap nvrtr (nt a prticly gd chce for prcsn lctrncs, ncdntly), nd once mre I dnt knw of ny.

Gvn tht usng swtchrs wll ncsarly incrs ur cmpnt cnt by a mn of 2 ndctrs, u wld be bttr ff usn 3 dvcs with th assctd npt nd otpt caps (whch u wll nd wth an spply).

If ur npt is AC, u'll nd a rctfr in frnt of it as wll (as ll th othrs hre cld tll u).

Cheers

PeteS (Practicing language skills)