Heterostructure acoustic charge transport device model

A small-signal circuit model for heterostructure acoustic charge transport (HACT) devices is derived from experimental data. The model includes the device transconductance, impulse, noise, and nonlinear responses. Data are presented which show how the transconductance and the noise floor are related to the quiescent current in the transport channel. Noise power is also related to the number of electrodes in the output array. The measured transconductance is 0.2-0.5 mS/mm for devices operating at 144 MHz. The noise current density in the transport channel is shown to vary as the square root of bias current. The noise power density in the output circuit is shown to vary as the square of the number of output electrodes. Design rules are presented which can be used to predict the noise floor gain, compression point, and dynamic range for a HACT device based on its transconductance. >