I am creating a current source to try to expand my knowledge about electronics design. After some research I decided to build the Howland setup since I want to develop a bipolar current source. The circuit is shown below:
I have created a breadboarded setup of this circuit, and the voltage signals I measure at Vload1 and Vload2 have a DC offset of approximately 1.5V and 2.3V respectively. I have tried varying the frequency between 10kHz and 100kHz, as well as varying the load between 500-4000 ohms. The offset voltages varied by a few hundred mV during these tests. I am wondering if anyone may know what could be causing the DC offset?
- When I simulated this circuit in LTSpice there is no DC offset. In my first simulations I got the "Singular Matrix" error, at which point I added ".options gshunt 1e-16". I realize this connects the nodes to ground via a shunt conductance, so I have also tried ".options gfloat=0", but this didn't result in any offset occurring.
- I have tested the physical circuit with only one current source driving a grounded load, and no offset occurs (which is expected).