DocumentCode :
1210797
Title :
Bandwidth Potential of Cascode HBT-Based TWAs as a Function of Transistor 
Ratio
Author :
Meliani, Chafik ; Rudolph, Matthias ; Doerner, Ralf ; Heinrich, Wolfgang
Author_Institution :
Ferdinand-Braun-Inst. fur Hochstfrequenztechnik, Berlin
Volume :
56
Issue :
6
fYear :
2008
fDate :
6/1/2008 12:00:00 AM
Firstpage :
1331
Lastpage :
1337
Abstract :
The bandwidth potential of cascode HBT-based broadband amplifiers following the traveling-wave amplifier (TWA) concept is studied. An approximate expression for the gain of the circuit is derived, which is based on the transistor small-signal model and the artificial transmission-line parameters. In this way, a relation between the HBT cutoff frequencies fT and fmax and the 3-dB cutoff frequency fc of the amplifier is obtained. This is very useful for assessing the gain-bandwidth potential of a given HBT technology for cascode-based TWAs. Applying these results, we study the potential of two technologies with different fmax / fT ratios, an InP technology with fmax / fT of 120 GHz/190 GHz, and a GaAs technology with fmax / fT of 170 GHz/36 GHz. The higher influence of /max (compared to ft) on fc is quantitatively demonstrated. TWAs in both technologies were realized and measured, and good agreement between measurement and theory is obtained.
Keywords :
III-V semiconductors; gallium arsenide; heterojunction bipolar transistors; indium compounds; transmission lines; travelling wave amplifiers; GaAs; HBT cutoff frequencies; InP; artificial transmission-line parameters; broadband amplifiers; frequency 120 GHz; frequency 170 GHz; frequency 190 GHz; frequency 36 GHz; gain-bandwidth potential; transistor small-signal model; traveling-wave amplifier; ${ f}_{ T}$ ${ f}_{max}$
fLanguage :
English
Journal_Title :
Microwave Theory and Techniques, IEEE Transactions on
Publisher :
ieee
ISSN :
0018-9480
Type :
jour
DOI :
10.1109/TMTT.2008.921747
Filename :
4511508
Link To Document :
