In h parameter analysis, we take the input current and output voltage as independent variables. and the Input voltage and output current are dependent on the input current and output voltage. They are related as: Vin = h11Iin + h12Vout ___(1) Iout = h21Iin + h22Vout ___(2) In case of a transistor amplifier (say, common emitter RC coupled amplifier), practically say if we are feeding an input voltage (sine) to the amplifier using a signal generator, then Vin is decided by us. I would say Vin is not dependent on the output voltage of the amplifier. If this is the case, if we are doing h parameter analysis, I feel the use of Equation (1) becomes invalid as it suggests that the input voltage is dependent on the output. Because of this, I am not convinced with h parameter analysis of transistor circuits. Someone please help me with this?