The (complex) impedance presented to the output port of a device. Load impedance determines output power, linearity, and efficieny. It influences device gain and stability.
For maximum gain (minimum output reflection coefficient), L = s22'*
[The load impedance is equal to the conjugate of the output reflection coefficient, modified by any loading from the generator impedance.]
For power, L is set to present the correct load line to deliver the desired output power.
[L for power is a function of desired output power, bias point, and device parasitics. It can be approximated by the desired load impedance RL in parallel with the output capacitance at half operating voltage (CCB @ VCE/2), that combination in series with the output inductance (bond wires plus package parasitics). For class C (non-linear operation), RL ~ (VCE-VCsat)2/2Pout. For class A (linear operation), RL ~ (VCE-VCsat)2/7Pout.
Gain, Generator Impedance, Impedance, Impedance Matching, reflection coefficient, s-parameters