Impedance model of one-carrier space-charge limited current (SCLC) has often been applied to explain some experimental features in organic light-emitting diodes (OLED). However double injection current occurs in working devices and the impedance model has not been studied so far. We analyze the problem of double injection SCL current in the limit of infinite recombination. In order to obtain the ac response of a biased OLED we solve the equations for time dependent double-injection of space-charge-limited currents. We give an analytical expression for impedance as a function of frequency. Calculations predict values for the static capacitance C(ω→0) similar to those encountered in case of one-carrier SCLC, in which C/Cg=0.75 (being Cg the geometric capacitance), but shifted to higher frequencies. We give the equivalent circuits representing the limits at low frequencies. This model will help to understand the behavior of two carrier devices.