Datasheet ADCA3950 (Analog Devices) - 9

Data Sheet ADCA3950 THEORY OF OPERATION
The ADCA3950 is a 75 Ω input and output matched module The ADCA3950 is unconditional y stable and includes transient designed for CATV applications. The ADCA3950 uses cascode and surge protection circuits for robust operation in systems field effect transistor (FET) feedback amplifiers in a Class A targeting DOCSIS 3.1 and legacy DOCSIS standards. push pul configuration. The bottom half of the cascode stages are implemented in a single-die linear FET process that minimizes parasitics, thereby enabling higher gain. The top devices in the
75Ω 75Ω
cascodes are implemented using a linear GaN process able to swing high RF voltages. The frequency of operation is from 45 MHz to 1218 MHz. 11 0 Internally, the ADCA3950 module uses a balun to convert the 25049- input signal to a balanced signal that feeds the active stages. Figure 10. Simplified Schematic An output impedance transformer and balun combination converts the balanced GaN signals to an unbalanced 75 Ω output. The output transformer also feeds the dc to the active stages and cancels second-order distortion products coming from the active devices. Rev. 0 | Page 9 of 11 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS GENERAL PERFORMANCE DISTORTION DATA (ALL DIGITAL CHANNEL PLAN) DISTORTION DATA (MIXED SIGNAL CHANNEL PLAN) ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS S-PARAMETERS 18 dB TILT PERFORMANCE THEORY OF OPERATION APPLICATIONS INFORMATION OUTLINE DIMENSIONS ORDERING GUIDE