Noise measurements on single electron transistors using bias switching read-out

We present a simple bias reversal technique for single electron transistors (SET) to remove fluctuations of tunneling resistance from the read-out sig nal at lo iu frequencies. The gain of the device is kept constant under bia s reversal by using asymmetric junction capacitances. In our Al/AlOx/Al dev ices with 1.2 mum island size and 100 x 100 nm(2) tunnel junctions, the noi se at 10 Hz is 6 x 10(-4)e/root Hz, independent of the bias modulation.