OPA860: best for generating a low amplitude (1 mA) sinusoidal current between 50 - 100 kHz.

Hi Marvin,

not to forget the LM13700

Can you post a scheme how the customer wants to program the frequency and amplitude of this sine wave? And what distortion is the sine wave planned to offer?

Kai

Any update?

Hi Kai,

Thank you for following up.

I am still waiting for the customer to share the information you requested.

I will get back to you once they respond.

Thanks and regards,

Marvin

Hi Kai,

Thank you for your patience. I received a response from the customer just now. Please see details below:

Hi Marvin,

I think the best method here would be to use the "improved Howland current pump". The OPA860, on the other hand, is not as precise as the Howland current pump and is more something for very high speed applications.

Kai

Hello Marvin and Kai,

  Thank you for the additional information and explanation. The application does lean towards needing a precise design than what the OTAs listed above will offer. Most of these devices were provide faster responses and higher current output. 

  Here are resources on Kai's suggestion Howland current pump vs Improved Howland Current pump:

1. Would start at this brief overview link which explains how output current is generated regardless of the voltage drop over the variable load 
2. A Study on Howland and Improved Howland current pumps with section on choosing the right amplifier
   1. Will depend on common mode voltage range and distortion performance as Kai asked above 
   2. Will probably need a rail-to-rail voltage feedback amplifier with zero-crossover distortion
3. Analog Engineer's Circuit Cookbook on Designing Improved Howland current pumps with buffer
4. Analysis on the variations of the improved Howland current pump 

   I am moving this thread over to precision amplifier team to help narrow down the amplifier. 

Thank you,

Sima

Hi Sima, hi Marvin,

well, for properly designing the Howland current pump we would need to know the load. The load impedance times the 1mA current will give the output voltage the current pump has to be able to handle. And from the output voltage the necessary supply voltage can be concluded.

Kai