OP amp to drive LR circuit

Thread Starter


Joined Jul 7, 2009
I need to measure permeability of a powder. To do it I devise a simple device. I wound two coils on a hollow cylinder in which I put powder that I want to measure.

1.I generate 1000Hz sine wave with V=500mV on my laptop.
2. The signal gets amplified by class D audio power amp and fed into primary coil via 4 ohm sensing resistor. The coil has an inductance of 20 mH. I need to feed 1-1.2 A into the coil.
3. I measure voltage generated by the secondary coil which depends on the current flowing through the first coil and the magnetic permeability of the core (powder).
My cheap power amp has a pretty high DC offset so when there is no sin wave generated I still measure 150mV across sensing resistor. I’d like to replace it with an op amp that can drive my circuit but I’m not sure if such powerful op amp exists.