Balancing Algorithm for a Digitally Controlled Multistage DC Amplifier

The article describes a simple algorithm for semi-automatic balancing of a high-gain DC multi-stage amplifying path designed to study flicker noise. The basis of the measuring channel is a unified amplifying stage with digital control of the gain and bias voltage using a built-in microcontroller. The problem of initial balancing is relevant in those cases when the measuring path is made according to a multistage scheme and it is necessary to make a choice between the accuracy of setting the zero level at the output of the path and the dynamic range of balancing. In addition, initial balancing is often associated with saturation, which causes undesirable overloading of op-amps and electronic digital feedback potentiometers due to the unacceptably large through current caused by this saturation. This is especially true for the first stages of amplification, where the resistor values are very small to reduce the inherent noise of the stage. The need to take into account this factor significantly complicates the initial balancing procedure when matching the path with the signal source. The paper proposes and investigates a simple algorithm for sequential balancing of cascades based on built-in microcontrollers, which operates independently and in parallel with the algorithm for digital protection of potentiometers. It is shown that the use of the proposed algorithm makes it possible to achieve high accuracy of path balancing with simultaneous expansion of the dynamic range.