Single VDGA-Based Mixed-Mode Electronically Tunable First-Order Universal Filter

Abstract

This article presents a mixed-mode electronically tunable first-order universal filter configuration employing only one voltage differencing gain amplifier (VDGA), one capacitor, and one grounded resistor. With the appropriate selection of the input signals, the proposed circuit can realize all three first-order standard filter functions, namely low pass (LP), high pass (HP), and all pass (AP), in all four possible modes, including voltage mode (VM), trans-admittance mode (TAM), current mode (CM), and trans-impedance mode (TIM), from the same circuit structure. It also provides an electronic tuning of the pole frequency and the passband gain by varying transconductance values. Non-ideal and parasitic effect analyses of the proposed circuit were also carried out. PSPICE simulations and experimental findings have both confirmed the performance of the design. A number of simulations and experimental observations confirm the viability of the suggested configuration in practical applications.

Current-Mode First-Order Versatile Filter Using Translinear Current Conveyors with Controlled Current Gain

“…Several universal first-order filters are available in the open literature . It should be noted that the universal first-order filter is an interesting topic for publications because many papers on this topic were published in a few years ago [28][29][30][31][32][33][34]. Considering the mode of operations, these first-order filters can be classified as voltage-mode (VM) filters [6][7][8][9][10][11][12][13][14], current-mode (CM) filters [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], and mixed-mode (MM) filters [31][32][33][34].…”

“…It should be noted that the universal first-order filter is an interesting topic for publications because many papers on this topic were published in a few years ago [28][29][30][31][32][33][34]. Considering the mode of operations, these first-order filters can be classified as voltage-mode (VM) filters [6][7][8][9][10][11][12][13][14], current-mode (CM) filters [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], and mixed-mode (MM) filters [31][32][33][34]. This work is focused on CM filters that should provide low-input and high-output impedances, which is ideal for CM circuits because they can be connected to applications without buffer circuit requirements.…”

“…Considering CM and MM filters in [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34], only the circuits in [15,24] can realize six transfer functions into a single topology, namely, both non-inverting and inverting transfer functions of LP, HP, and AP are obtained. However, the current gain of these transfer functions cannot be controlled.…”

“…The first-order filter that can adjust the current gain of transfer functions has been proposed in [16], but only three transfer functions of LP, HP, and AP filters are obtained. The circuits that offer low-input and high-output impedances have been reported in [15,21,25,26,29], and several filters offer electronic control of the pole frequency [17,[25][26][27][30][31][32]34]. However, these first-order filters cannot control the gain of transfer functions, and some of these filters offer only three transfer functions LP, HP, and AP filters.…”

“…The circuits in [16,19,24] use a floating capacitor, which is not ideal for integrated circuits. The circuits in [29,34] require two identical input signals, so an additional current splitter circuit is needed.…”