Noise analysis of current amplifiers with a dynamic capacitor

Conclusions

• 1. Total noise in general consists of two components: low frequency thermal noise between nodes 0 and 2 (the first term in Eq. (1)) and tube noise at frequencyω _c (third and fourth terms in Eq. (2)). All remaining noise components are small enough to be neglected.

• 2. Capacitance C₉ has considerable effect on the signal/noise ratio. To raise the signal/noise ratio, C₉ must be decreased, C₈ must be chosen equal to C₉, g₂₃₅ must be reduced, andω _c must be raised. The condition C₈=C₉ is quite different from the recommendation current in the literature that C₈=C₅.

• 3. The relative advantage in the signal/noise ratio obtained by increasingω _c increases with an expansion of the system pass band.

This method of noise analysis can be used in studying various instrument circuits with dynamic capacitors.