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I am trying to build a bi-directional constant current source with a h-bridge configuration. As you can see in the attached figure, I am controlling the direction of current on the load using PWM command from micro controller. I have tried analog switch ICs(such as CD4016, CD4066) to simulate a +- 1 mA current driver. The simulation works very well, but when I implement this circuit with real electronic components the circuit does not work. Do you have any suggestions or thoughts on this problem. I have to add when I use transistors for switching there is no problem.

I have added another figure for clarification. This is the result of simulation. As can be seen the h-bridge circuit produce -+1mA at the load. V battery + provides the voltage and constant current source control the current. H-bridge circuit change the direction of current by switching on 1,4 in one phase and switching on 2, 3 in the second phase. This circuit produces the -+1mA shown in the picture. But in the real implementation of circuit I can not get any voltage across the load. I use 10 kohm load and measure current by connecting oscilloscope across the load.

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  • \$\begingroup\$ For a two-quadrant arrangement you might consider something like what is found here. The first idea shown there uses a voltage to control the two-quadrant current. But there is no reason you cannot use PWM to generate that voltage. Of course, I don't know exactly what you are trying to achieve. But at least perhaps you can clarify your question on the basis of that suggestion. \$\endgroup\$ – jonk Jul 6 at 6:27
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    \$\begingroup\$ 'does not work' is not helpful for diagnosis. What does it do, exactly? \$\endgroup\$ – Neil_UK Jul 6 at 7:16
  • \$\begingroup\$ Kepco used to sell 4-quadrant supplies. \$\endgroup\$ – analogsystemsrf Jul 6 at 7:42
  • \$\begingroup\$ We assume there is only 1 PWM output for say PWM1 and that is inverted for PWM2 to get +Icc, -Icc at some valid Vcm between Vdd,Vss \$\endgroup\$ – Sunnyskyguy EE75 Jul 6 at 8:00
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    \$\begingroup\$ does the 'scope share a ground with the circuit? Add your hardware scope connections and power supply connections to the schematic. \$\endgroup\$ – Neil_UK Jul 6 at 10:19

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