The car circuit comprises an infrared sensor, a 6 V AA battery holder (four 1.5 V AA batteries), a diode, and an L9110 bridge motor driver IC (integrated circuit). The diode is used to reduce the power supply voltage from 6 V to 5.3 V, which is near the 5 V required for the TTL (transistor transistor logic) IR receiver. Usually, the voltage of an AA battery is 1.4 V (not 1.5 V) or even about 1.25 V for rechargeable batteries. Also, the motor does not need high voltage. It can move very quickly at a supplied voltage of just 5 V.

One of the differential inputs of the bridge motor driver IC is connected to the 5 V power supply (the diode). The second differential input of the bridge motor driver IC is connected to the IR receiver. When the infrared light reaches the receiver the TTL output of the receiver changes from 5 V to 4 V. This creates a difference in the bridge motor driver inputs and causes the motor to move.