A Low-Power Wide-Linear-Range Transconductance Amplifier
A Low-Power Wide-Linear-Range Transconductance Amplifier
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低功耗宽线性范围跨导放大器
DOI：
10.1023/a:1008292213687
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发表时间：
1997
影响因子：
1.4
通讯作者：
C. Mead
中科院分区：
文献类型：
--
作者：
R. Sarpeshkar;R. Lyon;C. Mead
传统的亚阈值跨导放大器的线性范围约为±75 mV，对于某些应用来说--例如，电子耳蜗中的滤波器，需要处理无失真的扩音器和大的动态范围。我们描述了一种设计用于低功率(<；1µW)亚阈值工作的跨导放大器，具有较宽的输入线性范围。我们通过组合四种技术，通过加宽跨导与偏置电流之比来获得较宽的线性范围。首先，输入差动对晶体管的井端被用作放大器输入。然后，被称为源退化(一种常见技术)和门退化(一种新技术)的反馈技术提供了进一步的改进。最后，一种新的凸点线性化技术进一步扩展了线性范围。为了快速分析这种电路技术，我们给出了信号流程图。我们的跨导降低是在一个紧凑的13晶体管电路中实现的，而不会降低其他特性，如直流输入工作范围。在标准的2µm工艺中，我们能够获得±1.7V的线性范围。使用我们的宽线性范围的放大器和一个电容，我们构造了一个实验动态范围为65d B的跟随积分器。我们证明，如果放大器的噪声主要是热的，那么线性范围的增加会增加跟随器积分器的动态范围。如果放大器的噪声主要是1/f，那么其线性范围的增加对跟随器-积分器的动态范围没有影响。为了保持跟随器-积分器的带宽，功耗随着放大器线性范围的增加而成比例地增加。我们还给出了亚阈值指数参数随电流水平和栅体电压的变化数据，这应该是所有低功耗设计者感兴趣的。我们已经描述了我们的放大器在硅耳蜗中的用途[1，2]。
The linear range of approximately ±75mV of traditional subthreshold transconductance amplifiers istoo small for certain applications—for example, for filtersin electronic cochleas, where it is desirable to handle loudsounds without distortion and to have a large dynamic range.We describe a transconductance amplifier designed for low-power(< 1 µW) subthreshold operation with a wideinput linear range. We obtain wide linear range by widening thetanh, or decreasing the ratio of transconductance to bias current,by a combination of four techniques. First, the well terminalsof the input differential-pair transistors are used as the amplifierinputs. Then, feedback techniques known as source degeneration(a common technique) and gate degeneration (a new technique)provide further improvements. Finally, a novel bump-linearizationtechnique extends the linear range even further. We present signal-flowdiagrams for speedy analysis of such circuit techniques. Ourtransconductance reduction is achieved in a compact 13-transistorcircuit without degrading other characteristics such as dc-inputoperating range. In a standard 2 µm process,we were able to obtain a linear range of ±1.7V.Using our wide-linear-range amplifier and a capacitor, we constructa follower–integrator with an experimental dynamic rangeof 65 dB. We show that, if the amplifier's noise is predominantlythermal, then an increase in its linear range increases thefollower–integrator'sdynamic range. If the amplifier's noise is predominantly 1/f,then an increase in its linear range has no effect on thefollower–integrator'sdynamic range. To preserve follower–integrator bandwidth,power consumption increases proportionately with an increasein the amplifier's linear range. We also present data for changesin the subthreshold exponential parameter with current leveland with gate-to-bulk voltage that should be of interest to alllow-power designers. We have described the use of our amplifierin a silicon cochlea [1, 2].