DC to DC Step-up Transformer

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You cannot do this with just a transformer. DC does not conduct from the primary to the secondary of a transformer. Since what you ask for cannot be done with what you are looking for, the question now is what do you need?

If you are trying to take the power from one DC power source (AA battery) and convert this power to a different DC voltage power source then a DC to DC switching supply is what you need. To choose the correct supply you will need to know the voltage and maximum current will be needed at the output. You will also have to know the power available from your original DC power source. The drawback of this approach is that the output power will always be less than the power taken from the sole power source. You should also clarify if the output is isolated from the input. One also should know if the output is supposed to be regulated (constant voltage or current) as the input DC voltage changes.

If instead you are trying to track a small changing DC signal to a larger signal then what you are looking for is a DC amplifier. The gain desired must be specified for a circuit to be crafted. Usually a DC amplifier has at least two power sources available, the DC voltage to be measured and a voltage source slightly larger than the maximum output desired. The advantage of this approach is that very little power must be taken from the original DC signal. So the output power can easily exceed the power taken from the measured DC voltage.