Abstract
This paper presents two new inductorless differential variable-gain transimpedance amplifiers (DVGTIA) with voltage bias controlled variable gain designed in TowerJazz's 0.18 mu m SiGe BiCMOS technology (using CMOS transistors only). Both consist of a modified differential cross-coupled regulated cascode preamplifier stage and a cascaded amplifier stage with bias-controlled gain-variation and third-order interleaving feedback. The designs have wide measured transimpedance gain ranges of 24.5-60.6 dB omega and 27.8-62.8 dB omega with bandwidth above 6.42 GHz and 5.22 GHz for DVGTIA designs 1 and 2 respectively. The core power consumptions are 30.7 mW and 27.5 mW from a 1.8 V supply and the input referred noise currents are 10.3 pA/root Hz and 21.7 pA/root Hz. The DVGTIA designs 1 and 2 have a dynamic range of 40.4 mu A to 3 mA and 76.8 mu A to 2.7 mA making both suitable for real photodetectors with an on-chip photodetector capacitive load of 250 fF. Both designs are compact with a core area of 100 mu m x 85 mu m.