Synthesis of High-Input Impedance Electronically Tunable Voltage-Mode Second-Order Low-Pass, Band-Pass, and High-Pass Filters Based on LT1228 Integrated Circuits

Abstract

This paper introduces two new high-input impedance electronically tunable voltage-mode (VM) multifunction second-order architectures with band-pass (BP), low-pass (LP), and high-pass (HP) filters. Both proposed architectures have one input and five outputs, implemented employing three commercial LT1228 integrated circuits (ICs), two grounded capacitors, and five resistors. Both proposed architectures also feature one high-impedance input port and three low-impedance output ports for easy connection to other VM configurations without the need for VM buffers. The two proposed VM LT1228-based second-order multifunction filters simultaneously provide BP, LP, and HP filter transfer functions at Vo1, Vo2, and Vo3 output terminals. The pole angular frequencies and the quality factors of the two proposed VM LT1228-based second-order multifunction filters can be electronically and orthogonally adjusted by the bias currents from their corresponding commercial LT1228 ICs, and can be independently adjusted in special cases. In addition, both proposed VM LT1228-based second-order multifunction filters have two independent gain-controlled BP and LP filter transfer functions at Vo4 and Vo5 output terminals, respectively. Based on the three commercial LT1228 ICs and several passive components, simulations and experimental measurements are provided to verify the theoretical predictions and demonstrate the performance of the two proposed high-input impedance electronically tunable VM LT1228-based second-order multifunction filters. The measured input 1-dB power gain compression point (P1dB), third-order IMD (IMD3), third-order intercept (TOI) point, and spurious-free dynamic range (SFDR) of the first proposed filter were −7.1 dBm, −48.84 dBc, 4.133 dBm, and 45.02 dBc, respectively. The measured input P1dB, IMD3, TOI, and SFDR of the second proposed filter were −7 dBm, −49.65 dBc, 4.316 dBm, and 45.88 dBc, respectively. Both proposed filters use a topology synthesis method based on the VM second-order non-inverting/inverting HP filter transfer functions to generate the BP, LP and HP filter transfer functions simultaneously, making them suitable for applications in three-way crossover networks.

Two New and Improved Electronically Adjustable Voltage-Mode Multifunction Biquadratic Filters With Independent Control of Band-Pass, High-Pass, and Low-Pass/Regular Notch Filter Gains

“…ABBs have been published in the open technical literature [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22]. VM multifunction biquadratic filters composed of various highperformance ABBs, such as voltage differencing buffered amplifier (VDBA) [23], [24], [25], [26], current feedback amplifier (CFA) [27], [28], [29], [30], [31], [32], differential difference transconductance amplifier (DDTA) [33], voltage differencing differential difference amplifier (VDDDA) [34], voltage differencing differential input buffered amplifier (VD-DIBA) [35], [36], operational transconductance amplifier (OTA) [37], [38], [39], and LT1228 [40], [41], [42], [43], [44], can be found in the open literature and play an important role in various electronic systems. Biquadratic filters generally implement LP, BP, HP, RN and all-pass (AP) filtering ...…”

“…The focus of this study is the simultaneous implementation of LP, BP, HP and LPN/RN filters from the same configuration, providing independent control of their filter gains. Reviewing the technical literature published in [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], and [43], these circuits suffer from one or more of the following drawbacks.…”

“…4) No Q-value independent and electronic controllability [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [35], [36], [41]. 5) Inability to provide six filtering responses simultaneously in a single topology [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [35], [36], [37], [38], [39], [40], [41], [42], [43]. 6) Inability to provide independent gain control of BP, HP, and LPN/RN filters [20], [21], [22], [23], [24], [25], [26], [27], [28],…”

“…5) Inability to provide six filtering responses simultaneously in a single topology [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [35], [36], [37], [38], [39], [40], [41], [42], [43]. 6) Inability to provide independent gain control of BP, HP, and LPN/RN filters [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43]. 7) No experimental verification results for the designed circuit [20], [21], …”

“…Designing a specific circuit using commercially available ABBs is an attractive method to help verify the accuracy and performance of the designed circuit. Consequently, many filter and oscillator implementations have been designed in the open literature and demonstrated using commercially available integrated circuits (ICs), such as the AD844 [2], [6], [7], [8], [9], [12], [27], [28], [29], [30], [31], [32], and [60], LF356 [26], AD830 [34] and [36], AD8130 [35], MAX435 [61] and [62], OPA860 [63], [64] and [65], and CA3080 [26], [66], [67], and [68], LM13600 [69], [70], [71], and LM13700 [16], [33], [34], and [72], and LT1228 [10], [19], [37], [38], [39], [40], [41], [42], [43], [73], [74], [75], [76], and…”