对数域积分电路的噪声特性研究

Study of Noise Behavior in Log-Domain Integrator Circuits

介绍了瞬时缩展积分器的基本原理,对数域积分器是其中重要的一种。由于对数域电路是基于晶体管的对数指数缩展特性,且晶体管本身存在噪声源,使得它的噪声呈现出信号与噪声相互调制的特性,这与线性非缩展积分电路噪声为常数是有所不同。文中采用积分器框图形式,将噪声集中考虑为一固定噪声源进行分析,最后得出了甲类和甲乙类工作状态的对数域积分器信噪比SNR的计算公式。研究表明,只有甲乙类工作的积分电路可饱和到SNRmax,使其动态范围能比甲类状态电路的动态范围扩展很多。

The basic principle of instant companding integrator is introduced. In this area, one of the most important integrators is the log-domain integrator. Because the log-domain circuit is based on the log-exponential companding characteristics of transistors, and the noise sources exist in the transistor抯 interior, therefore, this gives rise to a phenomenon called signal-noise inter-modulation, which is contrasted with the constant noise in linear and non-companding circuits. In this paper, for both class A and class AB operation log-domain integrators, the signal-to-noise-ratio (SNR) expressions are derived from the block diagram of companding integrator and the noise is considered as coming from a centralized source. It is shown that the SNR saturates to a maximum value SNRmax with a class AB log-domain integrator. The dynamic range of class AB log-domain circuits can be substantially extended compared with class A log-domain circuits.