Annales des telecommunications-annals of telecommunications vol:48 issue:3-4 pages:224-232
This paper describes full cmos continuous time filter design techniques which can meet the specifications commonly set for GSM applications. First several cmos filter design techniques are overviewed. The OTA-C technique is discussed to some more detail. To overcome the main drawback of the lower total harmonic distortion in OTA-C techniques very linear operational transconductance amplifiers (OTA) are required. Such an OTA, together with the applied linearisation techniques is discussed. To fulfil high accuracy in cut-off frequencies of the filter an active tuning system is necessary. A new on-chip tuning system is presented. The paper concludes with a practical design example for the GSM system. Therein the different OTA-C techniques discussed are illustrated.