Print Email Facebook Twitter Linearity Analysis and Enhancement Techniques for the Base-Collector Capacitance Dominated Distortion in Bipolar Amplifiers Title Linearity Analysis and Enhancement Techniques for the Base-Collector Capacitance Dominated Distortion in Bipolar Amplifiers Author Van der Meulen, J.M.M. Contributor Groenewegen, M.W.A. (mentor) De Vreede, L.C.N. (mentor) Mattheijssen, P. (mentor) Van der Heijden, M.P. (mentor) Faculty Electrical Engineering, Mathematics and Computer Science Department Microelectronics & Computer Engineering Programme Microelectronics Date 2015-10-29 Abstract SiGe bipolar amplifiers are getting more competitive in terms of noise figure to GaAs amplifiers. However, the linearity of these amplifiers is still limited in view of these GaAs implementations. In order to address and overcome these linearity limitations, this thesis report will start demonstrating that the linearity of SiGe bipolar amplifiers for base stations applications is limited by the base-collector charge related distortion. More specifically, it will be shown that in a CE-stage, the Cbc distortion tends to limit the linearity when the exponential distortion has been canceled. Using cross-coupled capacitive Cbc compensation, the OIP3 of the CE-stage can be still improved when all other transistor properties are close to ideal. However, once the base-emitter capacitances are added to the transistor model description, this linearity improvement vanishes again. Traditionally, people overcome Cbc related constraints in a CE-stage by moving to a cascode configuration. However, it will be shown that in a cascode configuration the Cbc of the CB-stage becomes the limiting linearity factor, again under the assumption that exponential induced distortion of the CE-stage has been effectively canceled. To overcome the Cbc distortion in the cascode configuration, 3 different techniques have been developed in this report. The first technique, a dedicated out-of-band matching has been proposed to cancel Cbc distortion. However, when considering the complete cascode lineup, it proves that the out-of-band currents from the CE-stage interfere with this Cbc compensation. Different methods have been proposed for cancellation of these currents, but only the use of an intermediate transformer between the CE- and CB-stage seems to be the most promising option. The second technique developed aims for passive in-band Cbc compensation. A compensation circuit containing a series combination of an inductor, a resistor and a multiplied copy of the Cbc capacitance can give exact compensation to Cbc distortion in a limited frequency band, however it proves to be quite sensitive to device parasitics. The last technique studied is active Cbc compensation. By sensing the currents in the base of the CB-stage, the nonlinear Cbc currents could be injected into the circuit with opposite phase, creating a much more linear amplifier. However, practical implementations also need to be stable to avoid oscillation. Adding stabilizing elements in the base of the CB-stage connection increases interactions between the Cbc of the CB-stage and the stabilization network. Due to IM3 currents from the CE-stage and phase deviations between these currents and the IM3 current from the Cbc of the CB-stage, the OIP3 will not increase when the Mextram model has been used. Although many linearization techniques have been developed and extensively studied, improvements are still needed to come to more practical, robust and product proven linearity enhancement techniques. Consequently, in the concluding chapter clear recommendations are given for future research followed by the overall conclusions of this thesis work. Subject LNACbclinearityOIP3base-collector capacitancedistortionbipolar amplifiers To reference this document use: http://resolver.tudelft.nl/uuid:0a65aa95-264d-488e-a482-2179923d79aa Embargo date 2020-10-29 Part of collection Student theses Document type master thesis Rights (c) 2015 Van der Meulen, J.M.M. Files PDF Thesis_report_JMM_van_der ... _final.pdf 6.59 MB Close viewer /islandora/object/uuid:0a65aa95-264d-488e-a482-2179923d79aa/datastream/OBJ/view