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Constant current sources and capacitance

Hello,

I am using texas instrument's part number INA2133U and OPA 131 to build the constant current source. The following link will take you to the circuit and data sheet ( page 13, figure 16). The inverting input of the amplifier is grounded.

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I used 10uF capacitor in series with the resistor R to stop DC leakage current and my load has an impedance in the range of 10Kohm to

500kohm. My question is there is a chance that the capacitance offered by the capacitor and the load will stop the current source to shut off and there will be no biphasic wave will pass through the capacitor.

The biphasic waves are bipolar square waves of frequencies between

200Hz to 500kHz. Will it better to minimize the DC leakage using some trimming scheme at the INA2133 or capacitor will be ok?

If such thing capacitance exsists acorss the current source than what will be its value in my circuit and how can I measure it?

The value of R is 50KOhm. The Max Dac voltage is +/- 2. 5 volts peak to peak.

Thanks Regards,

John

Reply to
john
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The capacitor is in series with the load.

John

Reply to
john

No. What happens is the capacitor blocks our DC output, charges up, and stops at the rail.

What ever possessed you to put a capacitor in series with a DC output?

Good Luck! Rich

Reply to
Rich Grise

Hi,

So, you are saying that even if the capacitor is fully charged, it will not only stop DC but also will not let the ac or biphasic square wave pass through it..It will block DC and AC both.

Will it be good idea to add a resistor at the input of the capacitor and ground it. The resistor will stop the capacitor to get fully charged.

Thanks John

Reply to
john

f
y
Reply to
john

Reply to
john

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