Research On Low-Frequency Amplifier For Small Signal

For low noise amplification and high gain of weak signal at the output of the sensor, two kinds of circuit with discrete components and integrated operational amplifier based on the depth understanding of the small-signal amplifier are designed in the paper to meet the needs of the performance such as gain, impedance, noise and interference.The noise analysis of these two circuits includes transistor noise model and integrated operational amplifier models. which are used to calculate the noise. The theoretical results are showed that both circuits can achieve low noise performance in the weak signal conditions.In order to verify the feasibility of the designed circuits, circuit debugging which is tested by test equipment is carried out respectively. The static operating point test, the output voltage test and noise test are tested and recorded. The results of experiment are showed that the designed amplifier circuit not only can achieve high gain but also decrease the noise effectively.At the same time, circuit simulation software OrCAD/Pspice is applied to verify the correctness of the designed circuits from the point of simulation. In the use of sinusoidal excitation source, the static operating point analysis, AC analysis and noise analysis are carried out to achieve the circuit voltage gain, input impedance, output impedance, the equivalent mean square noise value and other simulation results. Compared with the theory analysis, the simulation results verify the theoretical feasibility of the circuit further.