Thank you Mark. I haven't found any other way to give negative reference as Vref so I am fine with the inverting opamp method. I still have some doubts. I need to generate Vout from 0 to +Vref (+18V), so I need to give only +18V as Vref and the opamp will invert it to -18V, is that right? Why a sinusoid of +10/-10V is given as Vref in R1A in Figure 20 and in caption it is mentioned Vout=0 to +Vref whereas near Vout it is shown to generate negative voltage also (the negative half of the sinusoid). In Figure 20 if I give +10V in R1A, will it not be suffice to generate Vout=0V to +10V?
How do I give +18V as voltage reference? Max. Vout available upto +10V only.