Drift Compensation in Transistorized Differential Amplifier (d.c.)

ABSTRACT

Emitter coupled differential amplifier with constant current feed is often used as the input stage in high gain direct coupled amplifiers. Although, the problem of zero drift can be partially solved by using matched pair transistors in such amplifier stages, but there is a limit to which drift compensation is achieved in such stages. The paper presents two methods by which further reduction in drift is possible in transistorized differential amplifiers. In both methods temperature sensitive devices are used for compensation of drift resulting from the change in ambient temperature. The circuits were analysed and the condition for minimum possible drift was found out mathematically. Finally the experimental results and the limitations of these circuits were discussed.