Noise in high-gain transistors and its application to the measurement of certain transistor parameters

Noise performance of a high-gain transistor is presented. It is shown that both burst noise and flicker noise in high-gain transistors are not as important as those in low-gain units. At very small biases, less than 10 µA for the given transistor, the limiting noise of the transistor is dominated by the shot noise. In the higher bias region the thermal noise of the base resistance is the dominant noise of the transistor. It is also demonstrated that from noise measurement the base resistance rb'b, the transconductance gm, and the small signal common emitter-current gain β can be accurately determined.     

Adaption of directly measurable transistor noise parameters to computer-aided noise analysis

A transistor is conveniently characterised by four real noise parameters available from outer-terminal measurements. This representation is easily implemented into a computer program for noise analysis. The Rothe-Dahlke noise circuit is used in connection with the adjoint-network concept, and no additional auxiliary nodes are required.     

噪声系数测量中的温度修正方法

一般配置非智能噪声源的噪声系数分析仪,当环境温度变化时,不能及时修正环境温度对噪声系数测量的影响。文中介绍了噪声系数的测量原理及影响噪声系数测量不确定度的各种因素。从Y因子法测量噪声系数的原理出发,详细论述并推导了环境温度变化时噪声系数测量结果的修正方法。通过补偿温度变化对测量结果的影响,提高噪声系数测量,特别是低噪声器件噪声系数测量准确度。最终通过实验数据验证了理论推导的正确性,提供了温度修正曲线。     

Low-frequency noise measurement and analysis in organic light-emitting diodes

Low-frequency noise characteristics of organic light-emitting diodes are investigated. Two noise components were found in experimental low-frequency noise records, namely: 1) 1/f Gaussian noise from device bulk materials and 2) an excessive frequency-related part of noise related to device interfaces or defects and traps. 1/f noise is said to be related to carrier mobility. Degradation, especially photo-oxidation of the electroluminescence polymer, is a possible reason that affects carrier mobility. The excessive part of noise is believed to be related to the carrier numbers and could come from the interface deterioration, defects and traps generation and furnish. The excessive part of noise increases much faster during device stress. This shows that the degradation related interface defects and traps is much faster.     

Direct parameter-extraction method for MOSFET noise model from microwave noise figure measurement

A new method for the determination of the four noise parameters of the metal oxide semiconductor field effect transistors (MOSFETs) based on the noise figure measurement system without microwave tuner is presented. The noise parameters are determined based on a set of analytical expressions of noise parameters by fitting the measured noise figure of the active device. These expressions are derived from an accurate small signal and noise equivalent circuit model, which takes into account the substrate parasitics, pad capacitances, and series inductances. On-wafer experimental verification is presented and a comparison with tuner based method is given. Good agreement is obtained between simulated and measured results for 0.5 × 5 × 16 μm, 0.35 × 5 × 16 μm and 0.18 × 5 × 16 μm (gate length × number of gate fingers × unit gate width) MOSFETs.     

Low-frequency noise in modern bipolar transistors: impact ofintrinsic transistor and parasitic series resistances

In modern submicrometer transistors, the influence of the internal base and emitter series resistances, on both the I-V characteristics and the LF noise at higher bias currents, becomes important. In this paper expressions are presented for the LF noise in transistors, where the influence of the series resistances has been taken into account. The expressions have been compared with recent experimental results from the literature obtained from modern submicrometer (heterojunction) bipolar transistors. At low forward currents the LF noise in such transistors is determined by spontaneous fluctuations in the base and collector currents. In most transistors at higher forward currents, the parasitic series resistances and their noise become important     

Three-port scattering parameters for microwave transistor measurement

A 1- 12-GHz swept-frequency nondestructive three-port s- parameter measurement system for small-signal characterization of microwave transistor chips is described and its merits are discussed. The parameter f/SUB s/ is defined as the frequency at which the transducer power gain becomes unity and is introduced as a useful and directly observable parameter for the s-parameter measurement system. Some measurement results for TI L-187 transistors are given and a physical interpretation of the s-parameter data is discussed.     

OTDR系统波形的分析及其在光纤测量中的应用

本文利用瑞利散射原理分析了脉冲信号和脉宽大于、小于回波时间的方波信号的回波信号波形,并利用数值模拟得到了其理论波形图。根据原理自主搭建了一套光纤光时域反射仪（Optic Time Domain Reflectometer,简称OTDR）,用通信中通用的1550nm激光波长对样品光纤进行了实际测量,得到了与理论模拟完全一致的实测波形。通过对实测波形进行降噪处理得到了高精度的长度测量值和损耗测量值。长度测量的相对误差仅为0.0085%,与直接测量值比较,光纤传输损耗的相对误差为0.086%,理论与实验表明该OTDR系统完全可以与工程用的OTDR系统相媲美,在工程技术和教学研究中具有一定的应用前景。     

Influence of transistor parameters on the noise margin of organic digital circuits

The concept of noise margin is crucial in the design and operation of digital logic circuits. Analytical expressions for the transfer curves of an inverter based on two depletion-mode p-type organic thin-film transistors (OTFTs) were calculated. Based on these expressions, the values for the noise margin of organic-based inverters were calculated. In this paper, the influence of the OTFT parameters on the noise margin is presented. Knowing that statistical variations of the transistor parameters are inherent to OTFT technology, these statistical variations are also taken into account. Finally, a circuit yield analysis is presented.     

The permeable base transistor and its application to logic circuits

The permeable base transistor (PBT), which has been fabricated and operated as a microwave device, is described. Numerical solutions of Poisson's equation and the continuity equation show that this transistor could be used as a very high speed switch in a logic gate. It is predicted that with this device in an inverter gate having a fan out of one, a gate delay of 2 ps and a power-delay product of 0.1 fJ are possible. The unique feature of this transistor is the use of a metal grating embedded in the single-crystal semiconductor. The voltage on this grating controls the current between the grating fingers. By proper choice of carrier concentration and grating dimensions, enhancement and depletion mode devices can be made which allow simple gate designs similar to those of nMOS to be used. The lithographic and metal grating fabrication technologies are already well advanced and appear capable of producing PBT integrated circuits. The crystal embedding techniques for placing the metal inside the crystal are new and need further development. In the design of gates and circuits the embedded metal layers will provide the advantage of an interconnect layer inside the crystal, which reduces the number of layers required on the top of the semiconductor surface.     

1/f phase noise in a transistor and its application to reduce the frequency fluctuation in an oscillator

The 1/f noise generating mechanism is discussed with the diffusion coefficient fluctuation in the base. Results of noise measurements of the phase and amplitude or average current noises and their correlation coefficient in collector current are presented. A possible noise reduction method is suggested, using the correlation between the phase and amplitude fluctuations simultaneously. Also, measurement of the frequency and average current fluctuations along with their correlation coefficient for transistor oscillators is presented. In this case, it is found that both fluctuations correlate with each other at low frequency. A frequency stabilization technique is discussed and a new method to reduce the frequency fluctuation is proposed for an oscillator using the correlation.     

多端口T/R组件的单通道噪声系数测试方法

多端口T/R组件输出端口的噪声由各个通道共同决定,要测试单独通道的噪声系数非常困难。提出了一种基于衰减器改变的多端口TR组件单通道噪声系数测试方法,消除了其他通道的噪声影响,实现了对单独通道噪声系数的测试。通过测试一个8通道T/R组件的各个通道噪声系数,与单独通道测试结果进行了对比,两种方法测试结果最大差异为0.08 dB,验证了该方法可以很准确地测量多端口网络的单通道噪声系数。     

半导体激光器参数综合测量法及其应用

本文描述一种激光器参数综合测量方法和实验装置,不需移动待测样品,能测量光强-电流特性、近场和远场、激射光谱等激光器参数,以及对器件的结构、发光位置、腔面完整性等进行观察。     

De-embedding the noise figure of differential amplifiers

Many radio-frequency circuits use differential topologies, whereas the instruments to evaluate them are inevitably single ended. Taking into account noise correlations, this work extends Friis' well-known equation for the noise figure of a cascade of two-ports to the case of three-ports, such as baluns, which surround a differential amplifier during measurements. The amplifier gain and noise figure may be accurately de-embedded with single-ended measurements on the cascade and on the baluns. The new formulas are experimentally validated     

Low-frequency noise and phase noise in MESFETS with LTG-GaAs passivation

We report measurements of the low-frequency noise and phase noise of conventional unpassivated GaAs metal semiconductor field-effect transistors (MESFETs) and of MESFETs fabricated using an overlapping-gate structure and the low-temperature grown (LTG) GaAs as a passivation layer. The noise of the LTG-GaAs passivated MESFET was found to behave quite differently from that of a conventional MESFET and to be significantly reduced at low offset frequencies. These observations are explained in terms of the surface passivating effect of the LTG-GaAs. Low-frequency noise measurements seem to support the idea that the LTG-GaAs passivation reduces the number of active traps, in particular traps with large activation emergies. These results indicate that LTG-GaAs passivation can substantially reduce the near-carrier phase noise of MESFET-based oscillators.     

A new calculation approach of transistor noise parameters as afunction of gatewidth and bias current

In this paper a new method to calculate the noise parameters of transistors T_i (MESFET or HEMT) as a function of gatewidth and drain-bias current is presented. This method needs the knowledge of the R, P, and C coefficients. It is based on the measurement of the noise parameters of a reference transistor T,_r at two bias points (I_ds1 and I_ds2), and the equivalent circuit elements' values of all transistors T_i. Using this method, the noise parameters (F_min, Γ_opt, R_n ) for two MESFET's T_i biased at another current I_ds3 are obtained. Good agreement between the predicted and measured noise parameters' values is obtained for a broad frequency range (4-20 GHz)     

High-frequency noise of the junction field-effect transistor

Based on Geurst's treatment of the high-frequency value of the admittances of the junction field-effect transistor, the high-frequency noise of the device has been computed, assuming that the noise source is of thermal origin. By applying an appropriate series expansion of the current it is possible to express the noise of the drain and gate current in terms of known quantities, as steady-state transconductance, gate capacitance, and frequency. At low frequencies the noise spectrum of the drain current is independent of the frequency and is much larger than the noise of the gate current; however, at high frequencies the noise spectra of the gate and drain current both vary by ω²and are of the same order of magnitude.