Improvement of high T/sub c/ SQUID performance using an integrated resistor

The performance of high T/sub c/ SQUIDs with resistively shunted inductances have been investigated. We find that the voltage modulation depth /spl Delta/V of shunted 83 pH SQUIDs is significantly larger than that of unshunted SQUIDs with similar parameters and increases with the parameter /spl gamma/=R/sub n//R/sub s/ as expected from theory (R/sub n/ is the junction resistance and R/sub s/ the shunt resistance). We also find that the conventional decrease of /spl Delta/V with SQUID inductance L can be eliminated leaving only the effect of the thermal noise flux. In this way /spl Delta/V=63 /spl mu/V has been achieved for a bicrystal SQUID at 77 K whose screening parameter /spl beta//sub L/=13. Noise measurements performed on this SQUID indicate that the resistor in circuit does not increase the noise.