that appears as a voltage on the anode electrode of the oled the voltage drop vel is transmitted to the third node n 3 by the fourth transistor m 4 to initialize the first capacitor c 1 and the second capacitor c 2 in a period t 2 the second scan signal sn 2 is in a low state and the emission control signal is in a high state so that a current does not flow in the oled since the second scan signal sn 2 is in the low state in the period t 2 the third transistor m 3 and the fourth transistor m 4 are still turned on since the third transistor m 3 is still turned on the first transistor m 1 is still operating as a diode connected transistor the voltage between the source and the drain of a diode connected transistor is equal to the threshold voltage of the transistor plus a value that is a function of the current flowing through the transistor since the sixth transistor m 6 is turned off during the period t 2 because the emission control signal is in the high state no current flows through the diode connected first transistor m 1 during the period t 2 such that the voltage between.