ABSTRACT
The role of signal processing is to isolate the required information contained in the output signal from the transducer and present it in a suitable form to the next stage of the system. Many transducers provide an output in the form of a current, which in many applications must be converted into a voltage signal. Logarithmic amplifiers using an npn transistor in the feedback loop will handle positive input signals only. Negative input signals can be accommodated by replacing the npn transistor by a pnp transistor. The maximum frequency that an operational amplifier can accommodate may be limited not by its frequency response but by the maximum rate of change of input signal to which it can respond. A chopper stabilized amplifier operates by separating the input signal into its high and low frequency components, each of which is then amplified separately before being recombined at the output.
