Optimisation of on-chip amplifiers for charge coupled devices

The main purpose of the on-chip amplifier in a CCD image sensor is to act as an interface between the floating diffusion, where the charge-to-voltage conversion takes place and the off-chip circuitry. In this paper; a two-stage source follower amplifier optimised for visible imager CCDs developed at Semiconductor Complex Limited (SCL) has been presented and its design criteria discussed. Three source follower amplifier configurations were designed and fabricated. Major layout issues have been discussed. The effect of design variables such as transistor sizes and transistor types and of biasing conditions on gain, output, impedance and power consumption of the amplifiers have been studied in detail.