The J2190A active filter presents a high impedance (approximately 150kOhms) minimizing the loading of the circuit being tested. The output impedance is 50 Ohms allowing low noise coaxial connections to all typical test equipment. The 0.1Hz-10Hz noise band is common for opamp measurements, voltage regulators and voltage references. Many application notes offer schematics of such a filter for test purposes. An engineer’s time is much too valuable to be spent building test equipment. We have created a 4th order high pass and 4th order low pass filter with an optimally flat response and 0dB gain. Additional filters can be cascaded for even sharper cutoff.