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AD8436 DC coupled

Question asked by zi2012 on Oct 15, 2014
Latest reply on Dec 15, 2014 by jstaley

I am working with an AD8436 on my prototype board. My power supply is +-15VDC. I have constructed the circuit in figure 40 of the data sheet http://www.analog.com/static/imported-files/data_sheets/AD8436.pdf. For DC operation I have removed the 0.47uF input capacitor and bridged pins 2 and 3. When I tested the circuit with the input attached to common, the output was 120mV. This offset would show when other DC voltages where applied to the input. I looked through the circuit with a volt meter to find that IGND was -59mV and my power supply is really +15.02 and -15.14. So I removed the 10Mohm and attached IGND to common. This resulted in the output showing 9mV when the input is common.

 

1. Despite the obvious increase in power consumption, can I leave IGND attached to common in a bipolar power supply scenario?

 

2. Any other recommendations on reducing voltage off set on the output?

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