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Current control capacitive load

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Mitalius:
Hello.
I'm making a medical device that must be attached to the patient.
CHANNEL_ISET changes its state to 100kHz.
If I put the resistor that signal is good. But when I connect the way to the body of signjal becomes sawtooth wave.
What can I fix in this scheme? Any ideas you have on this?

DickCappels:
Differentiate your signal before applying it to the current source circuit.

Rerouter:
The leads will have inductance, the human body will have capacitance, and there will be some resistance and a few other parasitic capacitances, equally some parts of the skin act line non linear resistances,

This circuit at a guess is intended to AC measure the resistance of a person,  instead you may wish to use something like a howland current source, with a dash of compensation so that any inductance in the wires, and capacitance in the person cannot cause ringing or signal degradation.

something like this: http://tinyurl.com/yc2vnt9t

or full link for later readers.


--- Code: ---http://www.falstad.com/circuit/circuitjs.html?cct=$+1+5e-9+45.7144713268909+58+5+50%0Aa+256+160+368+160+0+5+0+1000000+2.499914676267427+0.7934400248063249%0Aw+368+160+368+96+0%0Aw+368+160+368+224+0%0Ar+256+224+368+224+0+10000%0Ar+256+96+368+96+0+10000%0Ar+256+96+144+96+0+10000%0Ar+144+224+256+224+0+10000%0Aw+256+176+256+224+0%0Aw+256+96+256+144+0%0Ar+256+320+256+400+0+47000%0Aw+256+400+304+400+0%0Ag+256+400+256+432+0%0Aw+256+320+304+320+0%0Ax+187+67+217+70+4+24+R1%0Ax+300+67+330+70+4+24+R2%0Ax+185+259+215+262+4+24+R3%0Ax+298+259+328+262+4+24+R4%0AR+144+96+80+96+1+2+100000+2.5+2.5+0+0.5%0Ac+304+320+304+400+0+1.0000000000000001e-7+0.7934299896949569%0AO+368+160+480+160+0%0Al+256+320+256+272+0+0.00009999999999999999+0.000059137027491623215%0Ar+256+272+256+224+0+1%0Ac+256+176+144+176+0+1.0000000000000001e-7+-0.2762715787593846%0Ar+144+224+144+176+0+1000%0Ax+317+333+518+336+4+24+Skin%5CsAprroximation%0Ax+43+145+237+148+4+24+AC%5CsCompensation%0Aa+48+224+144+224+1+15+-15+1000000+1.0629814961692903+1.062992125984252%0Aw+144+224+144+272+0%0Aw+144+272+48+272+0%0Aw+48+272+48+240+0%0Ar+-32+208+-112+208+0+10000%0Ag+-32+272+-32+288+0%0Aw+-32+208+48+208+0%0AR+-112+208+-128+208+0+0+40+5+0+0+0.5%0Ar+-32+208+-32+272+0+2700%0Ax+0+296+46+299+4+24+Bias%0Ao+19+64+0+12290+1.8882847784322407+0.0001+0+1%0A
--- End code ---

Rerouter:
To better clarify, the point between R3 and R4 would be your output for your electrode, where it says out would be the measurement output.

The AC compensation values i pulled off the top of my head based on the range of inductance and capacitance I know myself to measure on average.

Mitalius:
Thank
I'll have to try this in the next version of the board.

May I know the formula for Iout?

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