Question

Design of Experiments

1-Why does it make sense that the Gain (in dB) for this circuit never went above 0 dB?

2-Another characteristic of the circuit that could have been determined is its impedance seen by the output. What is output impedance? If a resistor was connected in parallel with the capacitor, or, more generally, if the output of this RC circuit was used to drive a load, why would identifying the output impedance be useful?

Answer 1

1) Maximum gain of a circuit is always 1, so 20*log₁₀(1)= 0 dB. This the reason why the gain in dB never goes above 0 dB.

2) Identifying the output impeance is used to match the load impedance. Power delivered from a source to load would be maximum when the output impedance equals the load impedeance. Output impedance is also used to check whether maximum power is being transferred to the load or not.

The impedance that has been calculated from the output terminal by shorting any other independent voltage source in the circuit is called the output impedance. If there are any independent current source then it should be kept open while calculating the output impedance. To calculate the output impedance place a known voltage source at the output and measure the current supplied by it, the ration of the known voltage source and the supplied current is the output impedance.