Current/voltage conversion circuit using current converter

The attached figure shows a current/voltage conversion circuit using a current converter. The current sensitivity is set to 10mV/lmA. This current detection circuit has the characteristics of high sensitivity and can detect weak currents.

The low-frequency characteristics of the inductor L1 are determined by the load resistance VR1). An integration circuit composed of IC1 is added to the circuit to compensate for the low-frequency characteristics, which can improve the low-frequency characteristics. The adjustment of the conversion sensitivity is achieved by VR2. The function of VR1 is to adjust the low-frequency characteristics. However, the conversion sensitivity will also change when VR1 is adjusted, so VR1 and VR2 should be adjusted alternately during adjustment to make the frequency characteristics flat. The operational amplifier IC2 is a common-phase integration circuit, and its function is to offset the DC offset of IC1.

The power supply voltage of the circuit is ±15V, the current consumption is 20mA, the frequency range of the measurable current is 0.5kHz-250kHz, the output voltage is below 20Vp-p, and the operational amplifier is LF356N.

The inductor coil Ll is wound 50 turns of φ0.25mm enameled wire on the ferrite magnetic ring.