Hantek CC-65 Current Clamp Probe – Part 3 – Signal Chain, Improving BW and Noise

This is the 3rd (and final) part of a series of posts on the Hantek CC-65 current clamp probe. In part 1 we went over the probe structure and circuit operation, and discussed possible issues and improvements. In part 2 we’ve started measurements and modifications of the probe, focusing on the power-supply (PS) and the sensor bias circuit. That allowed us to achieve lower noise on the supplies and sensor bias, as well as extend the circuit operation down to lower battery voltage.
In this post I’d like to go into modifications of the actual signal chain. This consists of the amplifier structure at the heart of the probe, but will also touch on the offset cancellation circuit. The main goal from my point of view is to both extend its bandwidth (BW) by at least an order of magnitude, and reduce the equivalent input noise density so that limited BW measurements can be made on lower amplitude signals.

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