Generalised operational floating current conveyor based instrumentation amplifier

Abstract

This paper proposes two generalised instrumentation amplifier topologies which can operate in voltage, current, transadmittance, and transimpedance mode. Each topology is a two stage structure, wherein an amplifier is used as first stage in the first topology and a converter is employed in the second one. The second stage is difference amplifier for both the structures. The theoretical proposition is verified through operational floating current conveyor (OFCC). The effect of non-idealities of OFCC on system performance, in particular finite transimpedance and tracking error, is also analysed and corresponding mathematical formulation is presented. The functional verification is performed through SPICE simulation using CMOS-based implementation of OFCC. The experimental results using current feedback operational amplifier-based OFCC implementation are also included which are in close agreement with theoretical and simulated results.

A New Proposal for OFCC-based Instrumentation Amplifier

“…Figure 10 Various performance parameters such as CMRR, its bandwidth and CMRR gain bandwidth product (GBP), are compared for available references along with proposed topology parameters and are listed in Table 3. As the IAs given in [11], [12], [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] and the proposed one have been tested for different differential gains and at different power supply voltages, it is not fair to compare these on the basis of gain and power consumption.…”

“…e. Both VM and CM active blocks are employed in [29][30][31], [36], [37] therefore the bandwidth is governed by VM block. f. Component matching is needed in [12], [22][23][24], [27][28][29][30][31] for proper operation. [12 Figure 5(a)] and only two resistors without matching constraint.…”

“…The operational floating current conveyor (OFCC) [1] is a variant of current conveyor with attractive features of both high and low impedance at input and output ports which make it suitable for sensing both currents and voltage and providing the sensed variable in form of current and voltage. The OFCC has been used to develop variable gain amplifier [1], basic amplifier circuits (voltage, current, transimpedance and transconductance) [2][3][4], filters [5][6][7][8][9][10], instrumentation amplifier [11], [12], readout circuits [13], logarithmic amplifier [14], rectifier [15], and wheatstone bridge [16] in recent past.…”

“…Taking the later classification into consideration, the available IA may be viewed as voltage mode IA (VMIA), current mode IA (CMIA), transimpedance mode IA (TIMIA) and transadmittance mode IA (TAMIA). The available VMIAs [11], [12], [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41] employ various active blocks and are compared on the basis of number and type of active block, numbers of resistors/capacitors, input and output impedance, as shown in Table 1.…”

A novel Instrumentation Amplifier with high tunable gain and CMRR for biomedical applications

“…After extensive investigation of references , it is observed that only few IA are existing that uses current-mode ABB having both input and output as current i.e. I-I [24,[27][28][29][30][31][32][33][34] while V-V CMIA are given in literatures [16,17,30,33,[35][36][37][38], V-I CMIA in [16,17,33] and I-V CMIA in [25,33,39]. The different current mode blocks based IA have been designed based on MOS transistors biased in subthreshold region [24], , current operational amplifier (COA) [27,28], CDTA [29], current feedback operational amplifier (CFOA) [30], MOS based configuration [31], current difference buffer amplifier (CDBA) [32], operation floating current conveyor (OFCC) [33], second generation current controlled conveyor (CCCII) [34].…”