CMOS amplifiers usually offer inferior offset drift, CMRR, and PSRR specifications and therefore are not suitable for precision applications.

The 10-lead DFN package of the LTC6081 offers a shutdown function to reduce each amplifier’s supply current to 2♚.īipolar amplifiers can have low offset and low offset drift, but their nA level input bias current make them inappropriate for high input impedance applications such as photodiode amplifiers. The LTC6081 and LTC6082 have a gain bandwidth product of 3.6MHz, with each amplifier only consuming about 330♚ current for a supply voltage of 2.7 to 5.5V. Their 0.8µV/☌ maximum offset drift, 1pA input bias current,1.3µV p-p of 0.1Hz to 10Hz noise, 120dB open loop gain and 110dB CMRR and PSRR make them perfect for precision applications. The LTC6081 and LTC6082 are dual and quad low offset, low drift, low noise CMOS operational amplifiers with rail-to-rail input and output stages. Typically the larger the initial offset voltage of an untrimmed op-amp the larger the drift with temperature will be.CMOS Op Amp Outperforms Bipolar Amps in Precision Applications Note that there is no guarantee that the slope of the curve will not exceed +/-1.2uV degree C, only the average over the whole temperature range is guaranteed.Ĭheap general purpose op-amps will have much larger offsets and drifts, and often the drift with temperature and time is not specified, but the principle is the same. In practice the curve will be smooth and often will be monotonic. The total offset must not exceed +/-100uV at any point in that range and the offset at room temperature must not exceed +/-60uV. The temperature drift spec is usually done using the 'box' method, where an imaginary box drawn around the offset voltage graph from -40 degrees C to 85 degrees C has a height that is not to exceed 150uV, which represents 1.2uV/degree C. Here they specify the long term drift as typical 0.4uV/month, the maximum Vos over the entire temperature range and the maximum/typical drift with temperature. Here are some specs for a typical precision op-amp ( OPA177): Some early CMOS-input op-amps had significant long term drift if they were exposed to large differential voltages, but that's more the exception then the rule.Īt different temperatures, the offset voltage will be different, and the limits on that change are usually specified by a parameter such as TCVos, in microvolts per Kelvin. There will be some drift over time, but it should not be large for most op-amps. It should be fairly stable for a given chip, when measured at the same temperature, supply voltage and common-mode voltage (and assuming the chip is not damaged by overheating, electrical transients etc.).

Cmos op amp offset