| ??? 12/04/06 23:17 Read: times |
#128939 - It should work but... Responding to: ???'s previous message |
Dear Oliver,
5nA times 1Mohm (as drawn) is only 5mV. I would try and use a 100Mohm sense resistor. Yes I'm aware of this problem; therefore, I chose the amplifier which has very high gain up to x10000 time, so I have enough room to move. In addition to that, 100 Momh resistor is not available. If I make a series circuit of resistor then it prones to error due to inductance of the traces and numbers of resistors. You should also be aware that these very low bias currents are only specified at 20 deg C because the leakage currents double every 10 deg C. This applies to your amplifier as well as your DUT diode, and also to whatever protection circuit you decide to use. Even at elevated temperatures, the amplifier should be plenty good enough, but you may find diodes that pass one day and fail another day when the weather is hotter. My test will be done in the place ambien tempurature will not change a lot (AC unit is always on and tempurtuare is around 70deg Farenheit). Plus I have quite relax tolerance: acceptable from 5-19nA, anything more than 20nA will be rejected. Yes, I'll take into account the fact you pointed out when I test my circuit. Thank you for sharing your experience. Best regards, T.L |
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