How does a transistor amplify an AC signal (when it works on DC and cannot change current direction)? - Quora
![Major Brands H11AA1 Optocoupler AC Input 1 Channel Transistor with Base DC Output, 6-Pin, 6.86 mm W x 5.08 mm H x 8.89 mm L, Black (Pack of 10): Amazon.com: Industrial & Scientific Major Brands H11AA1 Optocoupler AC Input 1 Channel Transistor with Base DC Output, 6-Pin, 6.86 mm W x 5.08 mm H x 8.89 mm L, Black (Pack of 10): Amazon.com: Industrial & Scientific](https://m.media-amazon.com/images/W/IMAGERENDERING_521856-T1/images/I/21lUgagg6LL._AC_UF1000,1000_QL80_.jpg)
Major Brands H11AA1 Optocoupler AC Input 1 Channel Transistor with Base DC Output, 6-Pin, 6.86 mm W x 5.08 mm H x 8.89 mm L, Black (Pack of 10): Amazon.com: Industrial & Scientific
![Why is DC component ignored and AC analysis is used when obtaining input output impedance of a BJT transistor amplifier? - Electrical Engineering Stack Exchange Why is DC component ignored and AC analysis is used when obtaining input output impedance of a BJT transistor amplifier? - Electrical Engineering Stack Exchange](https://i.stack.imgur.com/jNqFD.png)