Design and Comparison of Two Lock-In Amplifiers Using Demodulators AD630 and ADA2200

Lock-in amplification is an effective technique to improve the signal-to-noise ratio (SNR) in the presence of overwhelming noise. Two lock-in amplifiers (LIAs) are designed using demodulators AD630 and ADA2200 respectively, with their performances compared. The LIAs can be implemented on a surface mounted PCB, including additional signal processing circuits, which have many advantages such as portability, versatility and small size. In order to improve the performances of LIAs, the influence of LIAs on the performance is analyzed in detail from the characteristics of different parameters such as reference signal, effective bandwidth, filter performance and linearity. Both theoretical analysis and experiments are carried out to validate the designed prototype of LIAs, and the advantages and disadvantages of LIAs based on AD630 and ADA2200 are compared.