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i'm in trouble trying to figure it out how to properly control a peltier cell using current control principle .

I'm using a sine wave to figure circuit behavior through 0 to 6V and 0.5HZ .

Take a look enter image description here

The problem is that the output voltage(BLUE) do not follow its input troughout (YELLOW) . enter image description here

i wonder if the discharge of mosfet capacitance is taking too much time to happen? how do i fix that? i've tried vary its gate resistor but nothing changes .

Thanks for your help ..

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  • \$\begingroup\$ When you said "AMP OP" did you mean "op-amp"? \$\endgroup\$ – The Photon Oct 11 '17 at 22:37
  • \$\begingroup\$ exactly . I'm using brasilian therms i'll edit asap :D \$\endgroup\$ – Luiz Henrique Marques Oct 11 '17 at 22:39
  • \$\begingroup\$ Your output stage can only source current not sink \$\endgroup\$ – sstobbe Oct 12 '17 at 0:00
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If you want to control the current in the Peltier device it should be in the drain circuit of the mosfet and a resistor in the source (where you currently have the peltier device).

Your circuit is currently feeding back the voltage across the Peltier device.

Also if there is any temperature difference across the Peltier device it will generate voltage even when unpowered - that is probably what you are seeing right now.

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