Mirrored enhanced Howland current source with feedback control.
Rev Sci Instrum
; 90(2): 024702, 2019 Feb.
Article
em En
| MEDLINE
| ID: mdl-30831761
An impedance spectrum is calculated by the ratio between an injecting current and a resulting measured voltage, which allows the extraction of electrical properties from the material under study. The current source is considered an essential block to deliver a controlled current to a wide range of working loads and large bandwidth. To comply with such requirements, the current source output impedance must be much higher than the load impedance at each discrete frequency within the range. However, stray capacitance from cables and circuitry reduce the output impedance, especially at higher frequencies. We proposed a modified mirrored enhanced Howland current source (MEHCS) by using the feedback technique for a wide frequency range applications on electrical bioimpedance. We implemented four MEHCS circuits [with/without multiplexer (MUX) and with/without feedback], and then the output current and impedance were measured up to 20 MHz. The proposed current source showed an improvement in the frequency response at lower and higher frequencies when compared to the standard circuit. The measured output impedance was 10 times higher in the proposed circuit than in the standard MEHCS. The use of a feedback also increased the bandwidth in almost one decade in low and high frequencies when loaded with a resistor of about 1 kΩ.
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01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Rev Sci Instrum
Ano de publicação:
2019
Tipo de documento:
Article
País de afiliação:
Brasil
País de publicação:
Estados Unidos