The Design of Extremely Low-Noise Camera-Tube Preamplifiers

The design of current amplifiers suitable for amplifying the signal of camera tubes (or other similar transducers) is presented. Excellent noise performance can be obtained especially at low frequencies. Only one adjustment is required for shaping the frequency response and a very large bandwidth can be obtained. Experimental results are given for an amplifier designed for a camera tube with 15-pF output capacitance. The measured equivalent input noise current of this amplifier is smaller than 1 nA in a 5-MHz frequency band. The bandwidth of the amplifier exceeds 10 MHz.