EVALUATION OF CMOS TIMER INTEGRATED-CIRCUITS FOR CRYOGENIC USE

'555' and '551' type CMOS timer integrated circuits have been evaluated for cryogenic use as resistor - capacitor (R - C) oscillators. First, the behaviour of 28 different integrated circuits (ICs) was compared between room and liquid nitrogen temperatures, under a variety of operating conditions. The behaviour of six of these ICs was then measured as a function of temperature over the range 80 - 320 K. All circuits operated reasonably well down to 80 K, with frequency variations within almost-equal-to +/- 2% at almost-equal-to 3 kHz. Tests on seven ICs at liquid helium temperature showed that they were not suitable for use at this temperature.