was a current source of impedance greater than 100k u03c9 driving the amplifier input whose impedance is less than 0 5 u03c9 the transresistance a dc value that was essentially constant through at least 500 mhz stays fairly constant near 400 u03c9 over the range 10 80k which was measured with a 50 u03c9 oscilloscope impedance typical transresistances for tlcabacuo and weakly pinned ybacuo amplifiers between 40k and 77k are 500 u03c9 and 490 u03c9 respectively the equivalent input noise current i n was measured using a follower low noise amplifier and power spectral computations the values at 10 hz are plotted in fig5 a along with an outline of the measurement arrangement shown in fig5 b system noise was measured without the amplifier in place and was found to be about 1 nv hz 1 2 at the output this was subtracted from the measured total output noise with the amplifier in place before referring it to the input over this temperature range i n does not change much but there is considerable uncertainty of u00b1 0 5 pa hz 1 2 in these noise values because of equipment limitations typical broadband down to u2248 100 hz noise current of far ir detectors are on the order of 1 pa hz 1 2 depending on pixel.