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# Analysis

## 1. 单管共射放大电路

![](https://2889346953-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-Le4Kw7maZEabKFjsC7z%2F-Lf5hWWAPXrS6pkg310z%2F-Lf5hiH5swcUPyz6DciU%2Fsingle-tube_common-emitter_amplifier_circuit.png?generation=1558112045761528\&alt=media)

$$V\_{cc} = I\_B R\_b + U\_{BE}$$

$$V\_{cc} = I\_C R\_c + U\_{CE}$$

$$I\_E \approx I\_C = \beta I\_B$$

## 2. 微变等效电路

$$r\_{be} \approx 300 + \beta \frac{26 mv}{I\_C}$$

## 3. 动态指标

$$A\_u = \frac{U\_o}{U\_i} = \frac{- \beta i\_b \cdot (R\_C // R\_L)}{i\_b \cdot r\_{be}} = \frac{- \beta \cdot (R\_C // R\_L)}{r\_{be}}$$

$$A\_u$$ 是放大倍数，对应的还有 $$A\_i$$