hi im trying to build a negative 5v supply which can deliver upto 300 milliamp using only the +ve 5v supply im using tc7660 and lmc7660 which converts positive 5v to negative 5v but the issue is it could not delever the current require the supply in the negative rail drops to 70 millivots for 1.5 milli amp, actually iam powering the ad620 IA with this positive and negative rail, the output of the instrumentation amplifier is correct only when i give the exact voltage to positive and the negative supply of AD620 for example if the positive is 5.25 the negative should be-5.25 only then the output is delivered as desired when there is a small difference in millivolt in the supply voltages of ad620 (eg +ve is 5.25, -ve is 5.10), then the output is not as per the calculation so i need a exact +ve and negative voltage i found lm2662 which says it can deliver upto 200ma output current but i could not get it in market. kindly help me out