基于光电二极管的前置放大电路噪声分析

在光电检测电路中信噪比是衡量电路性能的一个重要参数,因此有必要对前置放大电路进行噪声分析。首先给出了光电二极管和运算放大器的等效电路模型,并分析了光电二极管和运算放大器的噪声来源。然后采用分频段的方法计算前置放大电路的噪声,同时引入等效噪声带宽的概念。最后根据叠加原理和噪声理论,推导出了前置放大器的输出噪声计算方法。结果表明:该方法计算的结果与仿真结果相一致,误差较小。该方法的引入,对于元器件的选择和低噪声电路设计具有很好的参考价值。     

Gas discharge modulation noise in He-Ne lasers

This paper reports measurements on laser light noise and discharge current noise in a 6328 Å He-Ne laser. A cross-correlation experiment shows a strong correlation between the two noise phenomena, indicating that the laser light noise is caused by the modulation of the light beam by the discharge current noise. The discharge current noise has a spectrum with a sharp resonance at 40 kc/s that does not show up in the laser light noise. The noise is represented by an equivalent circuit. By measuring the two noise spectra and the absolute value and the phase of the cross-correlation coefficientcas functions of frequency, it is possible to evaluate some of the components of the equivalent circuit. The values thus obtained turn out to be quite reasonable, which supports the assumptions on which the equivalent circuit is based.     

一款JFET低噪声前置放大器的设计

在对级联网络及结型场效应管的噪声分析基础上,采用结型场效应管等分立元件设计了一款低噪声前置放大器实用电路。并对其幅频特性、输入阻抗和等效输入噪声进行了测量,结果表明其输入阻抗高达71Mn。等效输入噪声电压为0．7nV／√Hz,是一种适合于较高内阻传感器的较理想的低噪声前置放大器电路。     

An equivalent circuit for the noise in VHF triodes

It is the aim of this paper to show that the present Information about the response of vhf triodes to signals and to noise can be represented is an equivalent circuit consisting of an equivalent noise emf in series with the input and of an independent equivalent noise current generator with an admittance in parallel to it connected between grid and cathode.     

Equivalent circuit analysis of noise in bulk semiconductor devices

Equivalent transmission-line analogs may be developed to advantage for the analysis of noise in bulk semiconductor devices. We discuss first a transmission-line analog for the law of conduction and diffusion of a single species of charge carriers that experience small disturbances from equilibrium. Through the use of Nyquist's theorem it is possible to obtain the power spectra of the noise sources of the equivalent transmission-line circuit at thermal equilibrium. Next, an equivalent circuit can be obtained if there is more than one charge carrier. This circuit is generalized to the case of drifted carriers and applied to the metal-semiconductor-metal (MSM) diode and to the small-signal analysis of the Gunn effect. We show how the equivalent circuit for the Gunn effect gives, by inspection, a lower bound on the noise measure achievable with a Gunn diode. We find that the Gunn diode has noise measures exceeding the lower bound. A traveling-wave Gunn device achieves the lower limit.     

异质结双极晶体管高频噪声建模及分析

提出了一个T等效异质结双极晶体管高频噪声电路模型.该模型是对通常用在硅双极晶体管中的Hawkins噪声模型进行改进得到的,主要的改进包括发射极理想因子、发射极电阻、内部BC结电容、外部BC结电容和其它寄生元素对器件噪声性能的影响.为了从等效噪声电路模型中计算出精确的噪声参数,采用了噪声相关矩阵法来计算噪声参数,从而避免了在等效电路变换中可能产生的简化和复杂的噪声测量.进一步利用该模型分析了等效电路元素对器件最小噪声系数的影响,分析计算结果和物理解释一致.同时通过基于异质结双极晶体管器件物理的公式,给出了器件参数对器件最小噪声系数的影响.     

The noise performance of microwave transistors

Expressions for the noise parameters of microwave transistors are derived. The theory is based on a small-signal common-emitter equivalent circuit which includes a new basic noise equivalent circuit and the dominanting header parasitics. The theory is verified experimentally in the L-band (1 to 2 Gc/s) frequency range using Ge and Si microwave transistors. It is found that the header parasitics have little influence on the minimum noise figure, but do have large effects on the equivalent noise resistance and the optimum source admittance in the frequency region above about one-half of the series-resonant frequency resulting from the parasitics in conjunction with wafer parameters. For a quick evaluation of the noise performance, new approximate expressions are also given for the noise figure and for the optimum current which produces the lowest value.     

Extracting 1/f noise coefficients for BJT's

We present a method for extracting the BJT SPICE noise model parameters AF and KF based on a general analysis of the small-signal equivalent circuit and the role of the internal BJT noise sources. The analysis is valid even for transistors with poor current gain and large base-collector conductance, for which the output noise characteristics may not be dominated by base flicker and shot noise. The method consists of interpreting the measured 1/f corner frequency versus DC current data in terms of the BJT's internal noisy small signal equivalent circuit. Measured data is presented for an implanted-emitter and two polysilicon-emitter bipolar technologies     

Noise factor contours for field-effect transistors at moderately high frequencies

This analysis of noise behavior is based on an equivalent circuit for the junction field-effect transistor (FET) that was previously published [10]. Since all noise sources in this equivalent circuit are uncorrelated and all significant parasitic elements are already considered, one may apply an easy and direct calculation for the noise factor, which is carried out for the common source, common gate, and common drain configurations. As a result, the constant noise factor contours are represented as circles in the plane of the complex source admittance Y8. This plot of circles is valid above 1/f noise up to moderately high frequencies, and is arrived at by a frequency-dependent normalization of the axis. It is shown that the plot is fully characterized by two frequency-dependent values: the optimum source admittanceY_{8} {opt}and the minimum noise factor Fmin, both being derived from the small-signal equivalent circuit of the FET and the bias condition. The results are in agreement with the commonly held opinion that the noise factor does not differ very much for the three basic configurations [9]. Finally, the theoretical results are verified by measurements at 30 and 60 MHz.     

异质结双极晶体管高频噪声建模及分析

提出了一个T等效异质结双极晶体管高频噪声电路模型.该模型是对通常用在硅双极晶体管中的Hawkins噪声模型进行改进得到的,主要的改进包括发射极理想因子、发射极电阻、内部BC结电容、外部BC结电容和其它寄生元素对器件噪声性能的影响.为了从等效噪声电路模型中计算出精确的噪声参数,采用了噪声相关矩阵法来计算噪声参数,从而避免了在等效电路变换中可能产生的简化和复杂的噪声测量.进一步利用该模型分析了等效电路元素对器件最小噪声系数的影响,分析计算结果和物理解释一致.同时通过基于异质结双极晶体管器件物理的公式,给出了器件参数对器件最小噪声系数的影响.     

Noise equivalent circuit of a semiconductor laser diode

The noise equivalent circuit of a semiconductor laser diode is derived from the rate equations including Langevin noise sources. This equivalent circuit allows a straightforward calculation of the noise and modulation characteristics of a laser diode combined with electronic components. The intrinsic junction voltage noise spectrum and the light intensity fluctuation of a current driven laser diode are calculated as a function of bias current and frequency.     

Noise in transistor mixers

Starting from the physical sources of noise in junction transistors, an equivalent noise circuit for a high frequency mixer circuit is presented. By means of formulas which have been derived for normal amplifiers and mixers the noise current components in the collector circuit are computed. These noise current components at the intermediate frequency are due to diverse amplifying and mixing processes. The dependence of the derived noise factor upon working point, generator output resistance, frequency and oscillator voltage is verified. The noise figure exhibits a minimum not only as a function of the generator output resistance but also as a function of the collector direct current. The noise figure may be optimized by choosing appropriate values for the circuit components and the operating point. Finally, the application of the noise formula to a dc-stabilized mixer stage is presented.     

Small-signal equivalent circuit for IMPATT transistors

A lumped-distributed small-signal equivalent circuit of an IMPATT transistor, a 3-terminal transistor-like device having a base-collector junction operated as an IMPATT diode, is presented. The equivalent circuit is composed of RLC elements, two controlled sources and one transmission line. Characterisation of the device based on this model gives clear insight into the small-signal and noise behaviour of the IMPATT transistors.     

基于光电二极管反偏的光电检测电路的噪声分析

噪声性能是限制光电检测电路探测能力的重要因素,针对这个问题,设计了基于光电二极管反偏的光电检测电路并分析其电路噪声,分析噪声时,创新性地从光电检测电路结构出发,将整个电路等效为光电二极管、晶体三极管、运算放大器三个级联模块,详尽分析了每个模块的噪声来源及其相关因素,计算每个模块的输出噪声,最终得出整个电路的输出噪声电压模型。根据输出噪声电压模型,确定了电路的各项参数,预估电路的输出噪声电压,最后,搭建实际电路,测量电路的噪声性能,验证了输出噪声电压模型的准确性,实现低噪声光电检测电路的设计。     

An accurate analysis of noise in rectangular bipolar transistors including current crowding

An accurate analysis of noise in rectangular bipolar transistors is developed from a distributed model using a collective approach and the transport noise theory. In this model, emitter current crowding effect are taken into account and noise behaviour at intermediate and low values of source impedance is precisely described. The structure of teh equivalent lumped circuit is established, and the analytical relationships characterizing its elements in an extended range of current and frequency are given. It is shown that; (a) the active base region must be represented by a nonlinear impedance with a generalized thermal noise source; (b) for low source impedances the equivalent input voltage shot noise generator is higher than predicted by low injection theories. Furthermore it is found that emitter crowding induces a uniform and important decrease in (a) base impedance (b) thermal noise and (c) the correlation between shot noise generators of the equivalent lumped circuit. Finally it appears that classical low injection theories are valid when crowding occurs in transistors biased with high source impedances.     

Balanced switching converter to reduce common-mode conducted noise

Because conventional switching converters have usually used unbalanced circuit topologies, parasitic capacitance between the drain/collector of an active switch and the frame ground through its heat sink may generate the common-mode conducted noise. This paper proposes a balanced switching converter circuit, which is an effective way to reduce the common-mode conducted noise. As an example, a boost converter version of the balanced switching converter is presented, and the mechanism of the common-mode noise reduction is explained using an equivalent circuit. This good feature is confirmed by experimental results. The concept of the balanced switching converter is applied to some other types of switching converters.     

A new noise model of HFET with special emphasis on gate-leakage

A new temperature noise model, including the influence of a gate-leakage current on the noise performance of a microwave HFET, is presented. Based on an extended small-signal equivalent circuit of the HFET and three equivalent noise temperatures the noise model allows the exact prediction of the four noise parameters in a wide frequency range. The validity of the new model is demonstrated by noise measurements at room temperature. It is shown that the three equivalent noise temperatures are frequency independent and that one of them (T_p ) especially represents the noise contribution caused by the gate-current I_G. The advantages of the new model are clearly demonstrated in comparison with a well established temperature noise model     

A new extrinsic equivalent circuit of HEMT's including noise formillimeter-wave circuit design

In this paper, we propose a reliable extrinsic equivalent circuit of a high-performance high electron-mobility transistor (HEMT) to determine both the [S]-parameters and noise parameters in the millimeter-wave range from characterizations performed below 40 GHz. In the case of the conventional equivalent circuits, only three extrinsic elements have to be determined instead of (at least) eight. We show the validity of the proposed extrinsic equivalent circuit by [S]-parameters and noise figure measurements up to the W-band (75-110 GHz). The proposed equivalent circuit is reliable and is very well suited for the design of low-noise integrated circuits for millimeter waves