The possibility of using the nonlinear interaction of acoustic vibrations with a drifting plasma in a semiconductor for making a multifunction device which is simultaneously a converter of electrical signals into acoustic, a mixer, an intermediate-frequency amplifier and a controllable optimum filter is examined. The dependence of the amplitude-frequency characteristics of the device on the electrophysical constants of the piezoelectric and semiconductor, the geometry of the interdigital system and the control voltage is found in a one-dimensional approximation. The possibility of obtaining a negative input admittance for the system at the signal frequency is discussed.