Considerations and analysis of high-speed ADC acquisition system circuit design - News - Global IC Trade Starts Here 工业

Abstract: The design of the front-end circuit of 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 requirements, system architecture, and the internal structure of the ADC. The use of an amplifier or transformer as part of the ADC's front-end circuit, along with an analysis of the inherent characteristics of the ADC chip, significantly impacts system performance.

Key Words: Analog-to-Digital Conversion; Front-End Circuit; System Performance; Impedance Matching; Signal-to-Noise Ratio

0 Introduction: In high-speed IF sampling circuit system design, factors such as low noise, minimal waveform distortion, low power consumption, excellent gain control, high passband flatness, maximum transmission power, input drive capability, and minimal amplitude-phase imbalance are critical design objectives for engineers. Achieving these goals depends on the various circuit elements within high-speed AD acquisition systems. This paper examines the design and system parameters of front-end conditioning circuits in high-speed acquisition systems. By analyzing the inherent characteristics of the ADC, the form of the input signal, and the system configuration, this study aims to provide insights into how these factors affect system performance. It is hoped that this work will serve as a reference and guide for designing 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: The fundamental distinction between front-end conditioning circuits lies in whether they are active (amplifiers) or passive (transformers). Amplifiers, being active devices, consume power and generate noise, whereas transformers consume no power and produce negligible noise. Both types involve dynamic effects that need to be carefully managed.

1.2 Advantages and Disadvantages of Amplifiers and Transformers: Amplifiers are generally more versatile than transformers as front-end conditioning circuits. If maintaining DC levels is necessary, amplifiers must be used since transformers inherently operate in AC mode. Additionally, amplifiers are easier to configure for gain compared to transformers because their output impedance remains relatively independent of the gain setting. Furthermore, amplifiers offer a flat response across the passband without ripples caused by parasitic interactions typical of transformers. These features make amplifiers advantageous in many sampling applications.

On the other hand, transformers excel in scenarios requiring low power consumption and minimal noise. When dealing with high-frequency signals where the ADC input cannot accommodate excessive additional noise, transformers outperform amplifiers. Moreover, when the operating frequency exceeds 150 MHz, transformers typically maintain superior signal-to-noise ratio (SNR) and spurious-free dynamic range (SFDR) compared to amplifiers.

1.3 Considerations for Selecting an Amplifier Front-End Conditioning Circuit: Understanding the essential differences between amplifiers and transformers, as well as their respective strengths and weaknesses, is vital for choosing the optimal front-end conditioning circuit for a given application. This section summarizes the considerations involved in selecting either a transformer or amplifier to drive an ADC, providing practical guidance through a summary presented in Table 1.

[3]