Lec-63 Output Resistance of BJT Amplifier Using Hybrid Model | A E | R K Classes | Hindi |

[@navaneethdesai]

Sir, why do we short circuit the external source to find the output impedance??? And Why don't we short or open circuit anything while finding input impedance? Sir please can you give satisfactory reason for this.....

[@R_K_Classes]

Dear Student, Please watch thevenin theorem in NAS lecture series. Input impedance means complete circuit can be presented so we will not remove or short load resistance. Thank you 😊

[@navaneethdesai]

Then why do we short circuit the "external voltage source (Vs)" sir?

[@R_K_Classes]

All external sources are simply replaced by their internal resistance. Voltage source has zero resistance and current sources has infinite value. That's why we make short circuit Beta.