Properties of an idealized traveling-wave charge-coupled device

In order to ascertain the operating capabilities and drive requirements of the charge-coupled device (CCD), it has been analyzed as a sinusoidal traveling-wave device. From this model, it has been possible to show the drive requirements and the lower bound to power dissipated in the substrate of an operating CCD. Signal loss in the sinusoidal model is due solely to surface-state effects, and varies with the amount of charge being transported through the device. Signal attenuation in digital devices is significantly reduced by using ZERO´s that carry at least 10 percent as much charge as the ONE´s. Some numerical extracts from the calculations will help illustrate what one can expect from charge-coupled devices. These numbers apply to a CCD with a wavelength (bit length) of 72 µ and a channel width of 20 µ, being driven with a 10-V p-p sine wave at 10 MHz. The drive power, almost purely capacitative, is 27 µW/bit in the absence of a signal and 320 µW/bit carrying a charge of 10^-12C. Due to the motion of this charge through the device, at least 2 µW/ active bit must be dissipated in the CCD substrate. Under these conditions, a uniform surface-state density of 10¹¹states/cm².eV will cause signal attenuation of 1.5 percent per bit with an alternating series of ONE´s and empty ZERO´s. If the ZERO´s carry 0.2 10^-12C, the signal attenuation drops to 1 percent per bit. The reactive power estimates described here are expected to accurately reflect actual device requirements, apart from parasitics. Surface-state attenuation, which is relatively insensitive to frequency, will be supplemented at high frequencies by diffusion-limited transfer.