squid the circuit damps the junctions at frequencies that are too high for the operational amplifier but too low for the damping circuits 14 and 15 integrated in the squid circuit fig5 presents the circuit of an un or hg squid in a general case an essential feature of un and hg squids is that the damping impedance 20 of the junctions are subject to the rule that at low frequencies the real part of the impedance approaches infinity in other words the junctions cannot be damped at low frequencies at high frequencies the junctions can alternatively be damped by means of impedance 21 it is possible to connect across the coil 22 a separate damping system 23 which mainly consists of the impedance involved in the connection circuits of the squid or of separate damping elements placed at this point the impedance 24 across the squid represents the load impedance formed by the biasing circuit the next amplifier stage or a separate impedance fig6 illustrates the amplification of the output signal of a squid based on undamped josephson junctions squid 30 measures the output current of un squid 31 the current 33 flowing through resistor 32 produces a voltage bias on the un squid applied via the un squid input coil.