Flux to voltage transfer function and noise in double relaxation oscillation SQUIDs

Under the low-damping limit, flux to voltage transfer function and classical intrinsic noise expressions for both thermal fluctuation and relaxation oscillation in double relaxation oscillation SQUID(DROS)s can be obtained with numerical calculation. The expressions show that the noise has T/sup 6/5/ temperature dependence and that at low relaxation oscillation frequencies, /spl omega//sub r/, the noise has a 1//spl omega//sub r/ behavior, and then turns up and gradually saturates at very high frequencies comparable with the plasma frequency. The upturn point, which gives the optimum energy resolution, might be near 10 GHz for typical DROS circuit parameters.