Superconducting implementation of neural circuits is presented. A neur
on element is composed of a coupled-SQUID, which is a combination of a
single-junction SQUID and a double-junction SQUID. A synapse element
is composed of multiple double-junction SQUIDs. To demonstrate the abi
lities of these circuits experimentally, a 3-bit neural-based A/D conv
erter, which contains three neurons and three synapses, has been fabri
cated using a niobium integration technology. This is the first succes
sful implementation of both neuron and active synapse elements into a
superconducting neural network.