In the 1970s, when the bipolar transistor was the undisputed king of analog integrated circuits (ICs), most electrical engineers regarded the MOS transistor as a second-rate device for ICs: it was a good switch, but a mediocre amplifier. As a graduate student at UC Berkeley, under the supervision of Paul Gray, Yannis Tsividis had a very different vision. He saw the MOS transistor as the future star for mixed-signal ICs and was excited to prove to the world he was right. The opening gambit was his thesis work demonstrating the first fully-integrated MOS opamp. This single achievement propelled him to the top of his generation of researchers and earned him a Berkeley PhD degree, a teaching appointment at Columbia University and a consulting position at Bell Laboratories.
Khoury, J.; Banu, M., "Yannis Tsividis' Early Contributions to MOS Filters," Solid-State Circuits Magazine, IEEE , vol.6, no.4, pp.36,40, Fall 2014