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Part Number: LMC6482
Hi, I'm designing a Bio-Impedance Analyzer for which I need a current of 700mA at 50kHz and 100kHz. I have implemented the Howland current source using LMC6482, but I'm unable to get a constant current at the output. Is there a resistance combination that can get the desired value or is there any other issue?
This is my circuit
Precision Amplifier Applications - TI Tucson
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In reply to Alexander Davis:
I'm really sorry, the current specification was 700uA. This can be handled by the same op-amp?
In reply to Roha Farooq:
Even with the voltage adjustment I'm not getting a constant current, the current is in 10^-12-10^-13 range.
Also does the amplitude if input sine wave affect the output current. We are using 2 sine waves of 20kHz and 100kHz. W e did not face any problems in the DC circuit but AC is proving to be more tricky after each step.
I'm getting the following output.
My apologies for not replying to this sooner. I think the issue may be that there's no return path to ground for the output of your current source in your simulation. Using the attached TINA-TI simulation, I do see a ±700µA current waveform out at 50kHz. AC sweeps indicate that the bandwidth of this circuit is around 400kHz.
TINA Simulation File
The current showing at AM1 is less than 700uA (i.e. 495.7uA). Also when we continue the circuit forward,the currents drop down to pA's.
1.Exactly where do I have to take the current output so that it remains constant at 700uA.
2.Also when I plot the current, the current scale shows a value of 700mA.
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