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Design of Howland current sources using differential evolution optimization

Kaue Felipe Morcelles
Kaue Felipe Morcelles
, 
Lucas Hermann Negri
Lucas Hermann Negri
 and 
Pedro Bertemes-Filho
Pedro Bertemes-Filho
   | Dec 31, 2020
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Published Online: Dec 31, 2020
Page range: 96 - 100
Received: Nov 06, 2020
DOI: https://doi.org/10.2478/joeb-2020-0014
Keywords
© 2020 Kaue Felipe Morcelles et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

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).

Case Load [kΩ] Magnitude [%] Phase [°]
Case 1 0.0 0.62 −0.36
1.0 1.13 −0.65
2.0 1.63 −0.93
Optimized 1 0.0 0.52 −0.30
1.0 0.55 −0.31
2.0 0.57 −0.33
Optimized 2 0.0 0.56 −0.32
1.0 0.99 −0.57
2.0 1.42 −0.81

Electrical parameters required for designing the Howland current source.

Transconductance (Gp) 303.03 μS
Frequency Range 10 Hz - 1.2 MHz
Maximum Load (Rlmax) 2.0 kΩ
Supply Voltage (Vsat) ± 5.0 V
Input Voltage (Vin) 1.65 V
Operational Amplifier AD825

Output Current Error (Magnitude and Phase) for different Loads (at 1.2 MHz).

Case Load [kΩ] Magnitude [%] Phase [°]
Case 1 0.0 7.55 −4.32
1.0 13.50 −7.75
2.0 19.33 −11.14
Optimized 1 0.0 6.39 −3.67
1.0 6.91 −3.82
2.0 7.53 −4.01
Optimized 2 0.0 6.78 −3.87
1.0 11.95 −6.84
2.0 17.10 −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.

Case μ [kΩ] σ [kΩ] CV [%]
Case 1 16.26 1.18 7.25
Optimized 103.41 29.89 28.90
Optimized 2 18.67 2.05 10.96
eISSN:
1891-5469
Language:
English
Publication timeframe:
Volume Open
Journal Subjects:
Engineering, Bioengineering and Biomedical Engineering, Biomedical Electronics, Life Sciences, Biophysics, Medicine, Biomedical Engineering, Physics, Spectroscopy and Metrology
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