关于AGC指数函数产生电路的疑惑
时间：10-02
整理：3721RD
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最近看了一篇关于AGC指数函数产生电路的论文，a low power monolithic AGC with automatic DC offset cancellation for direct conversion hybrid CDMA transceiver used in telemetering。对文中关于指数函数产生电路有一点疑惑。
文中VGA的指数函数产生电路如下图所示：
关于这个电路的描述是这样的：The biasing currents of the VGA are varied by a simple gain controller, Fig.4. The controller is mainly composed of a differential pair. The currents, which flow in two current sources - M7&8, are controlled by M1&2. M3&4 are added to improve the VGA‘s gain in decibels which changes more linearly with the control voltage(Fig.5). The gate of M1&2 are connected to Vctr and ground respectively. By varying the Vctr from 0V to 1.5V, the gain of the VGA sweeps from minimum to maximum(Fig.5).
不知道这个电路的指数表达式是如何推导出来的?求高手解释
文中VGA的指数函数产生电路如下图所示：
关于这个电路的描述是这样的：The biasing currents of the VGA are varied by a simple gain controller, Fig.4. The controller is mainly composed of a differential pair. The currents, which flow in two current sources - M7&8, are controlled by M1&2. M3&4 are added to improve the VGA‘s gain in decibels which changes more linearly with the control voltage(Fig.5). The gate of M1&2 are connected to Vctr and ground respectively. By varying the Vctr from 0V to 1.5V, the gain of the VGA sweeps from minimum to maximum(Fig.5).
不知道这个电路的指数表达式是如何推导出来的?求高手解释
顶一下，求高手回答
帮顶，同问
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