Auxiliary Negative Voltage Source

EE JULY/AUGUST 1988 02 AUXILIARY NEGATIVE- VOLTAGE SOURCE Manycircuitsrequire,apartfrom the connectedgatesN2toNsincl.,functions usualpositivevoltagesource,anegative asasquare-wavegeneratorwithbuf- 5V supply from which only a small current isdrawn.Insuchcases,amainstrans- ofthesquare-wavevoltageis,duetothe former with twin secondary winding wouldbearathertoocostlysolution. The circuit proposed here generates a negative potential from a positive supply.Thissupplymayprovidebe- tween5and15V.Ifthecurrentdrawn from thissupplyissmallerthan1mA, the level of the negative voltage generated lies about 1.5 V below that of the supply voltage. Thus, if the supply is 5 V , the negative potential is - 3.5 V . Whenacurrentof2mA isdrawnfrom the supply, the difference between the twovoltagesincreasestoabout2.5V. Operation of the circuit is fairly simple. Gate Ni,in conjunction with parallel- useofCMOSgates,verynearlyequalto thesupplyvoltage.RectifierDi-D2en- sures that the alternating voltage is con...