High-Frequency Sections of Active Filters of Mixed-Signal SoC Based on Current Amplifiers

The sufficient conditions for the efficient use of active elements are formulated by analyzing the basic structure of second-order unit. The expediency of current amplifiers usage in HF and SHF filters is shown. The examples of a methodical nature are given and conclusions of application importance are formulated. 1. Introduction A modern mixed-signal systems on a chip (SoC) creating for communications and radio-technical systems are inextricably linked to the development of analog and analog-digital IP-blocks for a sufficiently accurate processing of HF and SHF range signals. Some of the basic components of these blocks are frequency filters, which are highly sensitive parametrically. As a rule, reduction of the parametric sensitivity causes the need to create fairly complex active elements, which consume much power. Exactly energy problems of precision filters reduce the attainable level of integration of the SoC and the area of practical usage. Typically, the frequency filter is designed for a specific task with given parametric and structural constraints that are defined by a specific technology. In HF and SHF ranges transimpedance amplifiers (voltage-current converters) are often used as the active elements for compensation of losses in the passive RC-circuits [1, 2]. However, the potentially achievable unity-gain frequencies of these elements give way to current amplifiers, thus ultimately limiting the product of the Q factor (Q) and the pole frequency ( ) with the existing restrictions on power consumption. That is why the potential properties of the filter based on current amplifiers have a practical perspective and require further theoretical research. At least, the limiting theoretical estimations are not yet available and practical recommendations are not formulated. 2. Problem Statement As a rule, to increase the stability of the frequency characteristics of high-order filters, additional intersection connections are used to ensure the minimization of sensitivity to the instability of the passive RC elements in the range of operating frequencies [3, 4]. In HF and SHF bands, this schematic approach is almost never used because of the high and usually not accessible requirements to a parasitic phase shifts of used active elements. In this regard, the cascading of the second-order sections remains the main direction of the implementation of the necessary poles and zeros of the desired transfer function [5, 6]. That is why improving of their parameters stability and reduction (minimization) of appropriate parametric sensitivities is the main way