The role of the preamplifier
1 Improve the signal-to-noise ratio of the system (preceding the detector directly, the transmission line is short, the distributed capacitance Cs is reduced, and the signal-to-noise ratio is improved)
2. Reduce the relative impact of external interference (signal pre-amplification is pre-amplified.)
3. Reasonable layout, easy to adjust and use (pre-adjustment is non-adjustable, main amplifier amplification adjustment multiple, forming constant)
4. Impedance conversion and matching (preamplifier designed for high input impedance, low output impedance)