Shielding of backgating effects in GaAs IC's by using Schottky metal, ohmic metal, and n--implant has been studied. Contrary to what is expected from the electrostatic principle, positive bias to the shielding bars enhances backgating. Negative bias to the Schottky shielding bars increases the threshold for backgating, effectively reducing the backgating effect. These phenomena are explained in terms of carrier injection controlled by the surface potential. The results indicate that backgating effects can be reduced through proper circuit layout.