Fast high precision analog-digital-converter for pulse spectroscopy

An ADC with the following specifications has been designed and constructed: 8192 channels, amplitude range 0.05 to 10 V, positive, conversion time 12 μsec, max. integral linearity better than ± 2.5 × 10 −4 , stability of channel-width 0.5%. In a modification of the linear capacitor discharge a coarse and a fine measurement is executed subsequently, combined of a fast discharge and an interpolation with a slow discharge. The address oscillator works at 20 MHz, the address register is advanced during the coarse measurement in steps of 64 channels and during the fine measurement channel by channel. The discharge current generators are switched in exact synchronism with the pulses of the address oscillator; a two-step-synchronizing circuit is used. Special circuits have been developed for the pulsestretcher, the current-generators, current-switches and the discriminator. The high degree of stability and linearity is achieved through the proper use of field-effect-transistors, linear integrated circuits and fast digital intergrated circuits (emitter-coupled logic). Details of the tests performed and the testing methods are given.