Operational characteristics of CMOS op-amps at cryogenic temperatures

The gain-bandwidth product, slew rate and power dissipation of four commercially available CMOS operational amplifiers were measured as a function of temperature between 77 and 300 K. The measurements were made with the circuits in continuous operation. A marked improvement in the gain-bandwidth product and slew rate were measured as the temperature was lowered but there was a corresponding increase in the power dissipated. With a 5 V supply, the slew rate and the gain-bandwidth product of each circuit showed a common behaviour of peaking between 105 and 135 K, and their increase was by a factor of 2 to 4.7 times their room temperature values. Both parameters decreased thereafter on further lowering of the temperature. The power dissipation showed a similar characteristic behaviour as the temperature was varied.