I'm trying to power a INA114 instr. amp from two 7805 regulators. Basically what I want is a signal conditioner/amplifier on one board requiring only four connections: Vpower+, Vpower-, Vsig+, and Vsig-. I've connected the 7805's so the output from the first joins the 'common' for the second, making this node 0V or ground for the rest of the circuit.
At first, it seems to work fine - the output of the two regulators are about equal and the total combined output reaches 10V at around 11.5V input from the main supply. But as soon as you cross this threshold, the output begins to go back down as you continue to increase your input voltage. i.e. at 12V input its under 9.8V output and at 13V input its around 9.5V. Why would it do this?
I also noticed that the second (upper) 7805 gets just a bit warm whereas the lower one stays room temperature. I haven't figure out what would cause that disparity.
Is this a plausible way to power an instrumentation amplifier?
edit: Forgot to attach a schematic.
At first, it seems to work fine - the output of the two regulators are about equal and the total combined output reaches 10V at around 11.5V input from the main supply. But as soon as you cross this threshold, the output begins to go back down as you continue to increase your input voltage. i.e. at 12V input its under 9.8V output and at 13V input its around 9.5V. Why would it do this?
I also noticed that the second (upper) 7805 gets just a bit warm whereas the lower one stays room temperature. I haven't figure out what would cause that disparity.
Is this a plausible way to power an instrumentation amplifier?
edit: Forgot to attach a schematic.
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