PRGT is a photosensitive device with resonant properties compatible with the elements of microelectronics and integrated optics. The photosensitive element is a single crystal platelet of CdS, the mechanical resonance of which determines the resonant frequency of the device. The flexural mechanical vibrations of the platelet excited from an a.c. light flux are detected and converted into an electrical signal by means of a MOS-transistor. Without optimization of the parameters of the device a mean value of the sensitivity as high as 3 A lm−1 was obtained reaching 10 A lm−1 for some devices for frequencies up to 3 kHz. A low frequency analyser for a laser Doppler anemometer is also described.

Photoelectrical resonant gate transistor /PRGT/

A resonant gate transistor with an active vibrator is described in which the mechanical resonance of electrostatically excited flexural waves in thin single-crystal piezo semiconducting platelets of CdS is used for obtaining a small-sized frequency selective device. The flexural mechanical vibrations of the platelet are transformed into electrical signals according to the principle of the vibrating capacitor, making use also of the high input impedance of a MOS transistor. The amplitude of vibrations of the platelet and consequently the amplification factor of the RGTAV for the input voltages is raised as a result of the acousto-electrical interaction of the flexural wave with the drifting electrons produced by an external d.c. voltage. A number of devices were made having resonant frequencies from 1 to 10 kHz, with a Q-factor as high as 100 and an amplification factor at resonant frequency of about 0 dB.

A resonant gate transistor with an active vibrator (RGTAV)

Results are given of experimental investigations on amplification of standing flexural waves in single crystal CdS platelets, both sides of which are rigidly attached. Experimentally obtained dependences of the amplification on the voltage and of the amplified vibration on the frequency coincide well with the theoretical calculations.



Es werden experimentelle Ergebnisse uber Verstarkung der Biegungswellen in CdS-Einkristallen, deren Enden starr befestigt sind, mitgeteilt. Die experimentell festgestellten Abhangigkeiten der Verstarkung von der Spannung sowie der verstarkten Schwingung von der Frequenz stimmen mit den berechneten theoretischen Abhangigkeiten gut uberein.

M. I. Borisov

Papers

Amplification of flexural waves in single crystal platelets of Cds