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Design of Howland current sources using differential evolution optimization

Journal of Electrical Bioimpedance
Volume 11 (2020): Issue 1 (January 2020)
By:
Open Access
|Dec 2020

Figures & Tables

Figure 1

Flowchart that describes the main steps of the optimization method.
Flowchart that describes the main steps of the optimization method.

Figure 2

Schematic circuit of the ground loaded modified Howland Current Source.
Schematic circuit of the ground loaded modified Howland Current Source.

Figure 3

Output impedance of the optimized and non-optimized Howland Source circuits.
Output impedance of the optimized and non-optimized Howland Source circuits.

Figure 4

Transconductance curve of the optimized and non-optimized Howland Source Circuit.
Transconductance curve of the optimized and non-optimized Howland Source Circuit.

Figure 5

Transconductance (a) magnitude and (b) phase curves of the Optimized Case 1 for three different loads.
Transconductance (a) magnitude and (b) phase curves of the Optimized Case 1 for three different loads.

Figure 6

Output current of the (a) Case 1 and (b) Optimized Case 1 circuits for three different loads and 1 MHz square wave input voltage.
Output current of the (a) Case 1 and (b) Optimized Case 1 circuits for three different loads and 1 MHz square wave input voltage.

Output Current Error (Magnitude and Phase) for different Loads (at 100 kHz)_

CaseLoad [kΩ]Magnitude [%]Phase [°]
Case 10.00.62−0.36
1.01.13−0.65
2.01.63−0.93
Optimized 10.00.52−0.30
1.00.55−0.31
2.00.57−0.33
Optimized 20.00.56−0.32
1.00.99−0.57
2.01.42−0.81

Electrical parameters required for designing the Howland current source_

Transconductance (Gp)303.03 μS
Frequency Range10 Hz - 1.2 MHz
Maximum Load (Rlmax)2.0 kΩ
Supply Voltage (Vsat)± 5.0 V
Input Voltage (Vin)1.65 V
Operational AmplifierAD825

Output Current Error (Magnitude and Phase) for different Loads (at 1_2 MHz)_

CaseLoad [kΩ]Magnitude [%]Phase [°]
Case 10.07.55−4.32
1.013.50−7.75
2.019.33−11.14
Optimized 10.06.39−3.67
1.06.91−3.82
2.07.53−4.01
Optimized 20.06.78−3.87
1.011.95−6.84
2.017.10−9.81

Monte Carlo simulation results (at 1_2 MHz), showing the mean output impedance (μ), standard deviation (σ) and the coefficient of variation (CV) of each case over 10000 runs using 0_05% tolerance resistors_

Caseμ [kΩ]σ [kΩ]CV [%]
Case 116.261.187.25
Optimized103.4129.8928.90
Optimized 218.672.0510.96
DOI: https://doi.org/10.2478/joeb-2020-0014 | Journal eISSN: 1891-5469
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Language: English
Page range: 96 - 100
Submitted on: Nov 6, 2020
Published on: Dec 31, 2020
Published by: University of Oslo
In partnership with: Paradigm Publishing Services
Publication frequency: 1 times per year
Keywords:
bioimpedance,
differential evolution,
Howland source,
optimization
Related subjects:
Engineering,
Bioengineering and biomedical engineering,
Biomedical electronics,
Life sciences,
Biophysics,
Medicine,
Biomedical engineering,
Physics,
Spectroscopy and metrology

© 2020 Kaue Felipe Morcelles, Lucas Hermann Negri, Pedro Bertemes-Filho, published by University of Oslo
This work is licensed under the Creative Commons Attribution 4.0 License.

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