# Common-Emitter Amplifiers

1. Sep 23, 2008

### electrical_ck

Quick question, i have a formula for finding rc (the ac resistance in the collector circuit) which is rc=RC(collector) is the parallel combination of RL I don't understand that for the example they have RC(collector resistor)= 12K ohms parallel to RL=50k ohms = 9.68K ohms.. someone explain the proper way to get 9.68k???? Thanks

2. Sep 24, 2008

### chroot

Staff Emeritus
Resistors in parallel add this way:

$$\left( 50k^{-1} + 12k^{-1} \right)^{-1} = 9.68k$$

- Warren

3. Sep 24, 2008

### electrical_ck

yeah I figured it out, just had never seen it in those terms, thanks warren!