The primary aim of the work described in this thesis was to examine the possibility of obtaining amplification from a transferred electron device oscillating in the limited space charge accumulation (LSA) mode. An X-band relaxation LSA oscillator circuit was constructed and initial tests revealed the presence of simultaneous oscillations at two unrelated frequencies the normal large amplitude oscillation, characteristic of the LSA mode and a subsidiary low amplitude oscillation at a higher frequency. Following this observation the higher frequency was suppressed and the circuit then used as a negative conductance reflection amplifier at the frequency of the suppressed component of oscillation. Typically a gain of about 15dB could be obtained over a 3dB bandwidth of 50 MHz. The characteristics of the amplifier are given together with measurements of the admittance presented to the non-linear conductance of the LSA diode. The general circuit behaviour suggests that the mechanism causing gain is the bulk negative conductance exhibited by the device when it is biased above the threshold voltage. A theoretical model has been developed to illustrate the features of such an oscillator-amplifier and the characteristics of this model are discussed in comparison with the experimental circuit performance.