一种正弦扫频式恒流源设计

Design of a sine sweeping current source

高纯度、高输出阻抗的正弦恒流源信号是生物电阻抗测量设备的关键部件。本文设计了一种具有1 MHz带宽的正弦扫频式恒流源,其中正弦波形发生器基于DDS芯片AD9833,采用了新型LPF芯片LTC1560-1进行低通滤波;电压电流源转换器在Howland电流泵的基础上改进,使其具备更高的输出电压柔量。时钟源和LPF采用了电源控制技术,可在系统闲置时关闭电源。该恒流源在便携式生物阻抗频谱测量仪的实际应用表明:新型恒流源具有更好的频谱纯度和幅值稳定度,更高的输出阻抗和电压柔量,更低的功耗。

Sine current source with high frequency purity and high output impedance is a key part in bioimpedance measurement instruments.This paper introduces a novel sine sweeping current source(SSCS) with the upper frequency limit of 1 MHz,which consists of a sine-wave generator(SWG) and a voltage-current convertor(VCC).The SWG is based on DDS chip AD9833 and low-pass filter(LPF) chip LTC1560-1,while the VCC is an improved version of the traditional Howland current pump with higher output voltage compliance.The power supply of the source clock and the LPF can be shut off by system controller at idle time.The application of the SSCS in a portable bioimpedance spectrometer proves that the new SSCS can provide better frequency purity and magnitude stability,higher output impedance and voltage compliance,and lower power consumption.