Abstract: The design of the front-end circuit for a high-performance ADC acquisition system and the inherent characteristics of the ADC itself are crucial to the overall performance of the system. Optimizing the design of a high-speed sampling system involves numerous factors, including application properties, system composition, and the structure of the ADC. Using an amplifier or transformer as part of the ADC front-end circuit, along with an analysis of the inherent characteristics of the ADC chip, plays a significant role in system performance. Keywords: Analog-to-digital conversion; front-end circuit; system performance; impedance matching; signal-to-noise ratio 0 Introduction: In the design of high-speed IF sampling circuit systems, low noise, minimal waveform distortion, low power consumption, excellent gain control, high passband flatness, maximum transmission power, input drive capability, and the lowest amplitude-phase imbalance are the optimization goals pursued by designers. Achieving these goals depends on various circuit links within high-speed AD acquisition systems. This paper examines the design and system parameters of front-end conditioning circuits in high-speed acquisition systems, analyzing how the inherent characteristics of the ADC, the form of the input signal, and the nature of the signal affect system performance. It is hoped that this exploration will serve as a reference and guide for the design of high-speed acquisition systems. 1 Analysis of the Influence of Amplifier or Transformer Front-End Conditioning Circuits on System Design: 1.1 Amplifiers and Transformers: As the fundamental difference between front-end conditioning circuits, amplifiers are active devices, while transformers are passive ones. Amplifiers, like all active devices, consume power and generate noise, whereas transformers consume no power and produce negligible noise. Both involve dynamic effect issues. 1.2 Advantages and Disadvantages of Amplifiers and Transformers: Amplifiers used as front-end conditioning circuits offer fewer performance limitations compared to transformers. If DC levels need to be maintained, amplifiers must be used since transformers are inherently AC devices. Additionally, amplifiers are easier to configure for circuit gain, as their output impedance remains essentially independent of gain. Furthermore, amplifiers provide a flat response across the passband without ripple, which is a result of transformer parasitic interactions. These factors make amplifiers a superior choice as sampling front-end conditioning circuits compared to transformers. On the other hand, as passive components, transformers boast low power consumption and low noise, making them unmatched in certain scenarios. When signals are high-frequency and the ADC's input cannot handle excessive additional noise, transformers outperform amplifiers significantly. Moreover, considering the trade-off between bandwidth and noise, transformers surpass amplifiers in maintaining SNR and SFDR when frequencies exceed 150 MHz. 1.3 Considerations for Selecting the Amplifier Front-End Conditioning Circuit: The essential differences between the two sampling front-end conditioning circuits and their respective advantages and disadvantages have been discussed. However, in practical circuit design, only one can be chosen as the actual front-end conditioning circuit. This article will consider the selection of transformers or amplifiers to drive the ADC and summarize the considerations and preferred solutions in Table 1. In conclusion, the choice between amplifiers and transformers depends heavily on the specific requirements of the system. Engineers must weigh factors such as noise, power consumption, bandwidth, and the need for DC level maintenance to determine the optimal solution. By understanding the strengths and weaknesses of each option, designers can achieve the best possible performance for their high-speed acquisition systems. Shanghai Janetec Electric Co., Ltd. , https://www.janetecelectric.com
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