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4 wire Impedance measurement

Category: Hardware

Can I use the circuit as shown in below pictures.( it is simulated in LTspice). Can you please review the circuit. I mean is it okay to use this circuit?

Our requirement is, we needed 1mA(rms) of constant current need to inject to load. In simulation it is working fine for different load values and with different frequencies.

Output voltage from AD5933 IC(1.98V(p-p) with 1.48 DC bias.

Output from Differential Amplifier

Constant current to Body generated by Improved Howald current source circuit(PS. I am measuring current across top of current_sense resistor).

Can we cascade this circuit with impdance measuring circuit as mentioned in below link.



  • Hi Vikram,

    I see no issue with the driving circuit.

    It's also fine to have another amplifier driving the internal TIA as long as its DC bias point is half the AD5933 VDD. Vin is at VDD/2 and RFB pin can swing from 0V to VDD if the PGA gain is 1. You can adjust Rin and RFB to maximize the use of the dynamic range of the ADC.

    Best regards,