Linearity of electrical charge injection into charge-coupled devices

The linearity of the electrical signal injection into charge-coupled devices (CCDs) has been studied by measuring the generated higher harmonic components of a sinusoidal input. Results obtained with various injection methods and device geometries have been compared. Best results, with all harmonic components more than 40 dB below the fundamental, have been obtained for surface channel devices with a potential equilibrium method in which the signal is applied to a second input gate, while the first input gate is held at a dc reference potential. Bulk channel devices show more distortions, which is a consequence of the changing charge distribution in the channel with varying channel potential.