Electrical Engineering is a free introductory textbook to the basics of electrical engineering. See the editorial for more information....  # The Alternating-Current Equivalent Circuit

Author: E.E. Kimberly

For the circuit of Fig. 27-13, the equation for plate current change is Also, Therefore, By simplifying the equation, we obtain

Since gmrp = μ,  Fig. 27-14. Equivalent Circuit Corresponding to the Circuit of Fig. 27-13 It follows, therefore, that a generator having a voltage μ Δee and connected in series with the anode would produce the same change Δtp in the plate current as Δeg in the grid circuit actually does. It is therefore feasible to replace the actual circuit with an equivalent circuit such as that shown in Fig. 27-14. The battery voltage Ebb is not shown because Δip is only the usable incremental part of the total plate current. If the simple equivalent circuit is to be used, it is necessary that the triode be operated on the linear portion of its characteristic.

If eg is a sinusoid, then Equation (27-12) may be written as a vector equation as follows: (27-13)

If the load contains inductance also, then Equation (27-13) becomes

where  The alternating component of plate voltage is The gain of the amplifier of Fig. 27-13 is then expressed as follows: Last Update: 2010-11-27