In one aspect, a buffer circuit comprises a source or emitter follower input stage and output stage. A load is provided between the stages which comprises a representation of an output load of the buffer circuit. This improves the circuit linearity whilst enabling a high input impedance to be obtained.;In another aspect, a buffer circuit comprises a source or emitter follower output stage. A load is in the form of a filter is provided and which comprises a representation of an output load of the buffer circuit.