How do you determine the Thevenin equivalent of a circuit seen by a load?

How do you determine the Thevenin equivalent of a circuit seen by a load?

• A. Deactivate loads, find open-circuit voltage V_th; turn off independent sources to obtain R_th; connect the load to V_th and R_th.
• B. Short circuit the load and measure current; use that current as V_th.
• C. Compute R_eq with all sources active and connect the load directly.
• D. Use Norton’s equivalent and ignore the load during calculation.

Answer: (A)

To determine the Thevenin equivalent seen by a load, you first find the voltage across the open terminals with the load removed. This open-circuit voltage is V_th, the Thevenin voltage. Then you find the resistance seen from those same terminals after turning off all independent sources (voltage sources become shorts, current sources become opens; dependent sources stay active). The resulting resistance is R_th. Replacing the original network by a voltage source V_th in series with R_th gives the Thevenin equivalent seen by the load. If the circuit has dependent sources, you may need to apply a test source to determine R_th.

To determine the Thevenin equivalent seen by a load, you first find the voltage across the open terminals with the load removed. This open-circuit voltage is V_th, the Thevenin voltage. Then you find the resistance seen from those same terminals after turning off all independent sources (voltage sources become shorts, current sources become opens; dependent sources stay active). The resulting resistance is R_th. Replacing the original network by a voltage source V_th in series with R_th gives the Thevenin equivalent seen by the load. If the circuit has dependent sources, you may need to apply a test source to determine R_th.