I need to apply a current in the body by two electrodes and then analyze this signal, I will receive the signal by other 2 electrodes and amplify using a instrumentation amplifier using three Op Amps (TL084CN). But, I can not to simulate the offset by voltage controlled current source in a instrumentation amplifier.
I am using the topology described in the article "Design of an Instrumentation Amplifier - Justin Bauer", where the gain is 10. Example: With Vin = 500mV peak to peak, then Vout = 5V peak to peak. (Gain = 10). Putting 5V DC on Vref, then Vout is oscillating between + 10V and 0V. All right.
My problem is: Using a current source (Mirrored Modified Howland Current Source (MMHCS)) where +Iout = 1mA and -Iout = -1mA. With a initial voltage source where amplitude = 2V and the frequency = 1kHz. I can not to simulate the offset. Vout is always between + 10.5V and -10.5V. I tried to apply in Vref 10V, 5V, 2V, but nothing works. The Vout still varies from -10.5V to + 10.5V. The Vref only distorts the voltage signal. I want the Vout varies between (say) + 20V and 0V, it will use the AD converter Arduino Uno, that just read positive signs. I am using Proteus 8.5.
What am I doing wrong?
Sorry my poor english, i don't speak english.