A computerised tomographic scanning apparatus including a current amplifier.

摘要

The current amplifier (E) is designed for use in conjunction with computerized tomographic scanners (A) or other apparatus. The amplifier (E) comprises a differential amplifier with a first input connected to a photodiode or other source of current to be amplified. An integrating amplifier is connected between the differential amplifier output and a second differential amplifier input. The integrating amplifier has a time constant which is long compared with the period during which the diode current is to be amplified to provide automatic drift correction. A feedback loop connects the output of the differential amplifier with the first input. The feedback loop comprises a pair of matched transistors interconnected to form a current mirror. A first resistor connects the current mirror with ground. Current flow through these two resistors is summed to form the current flow received by the current mirror. The current generated by the current mirror forms the amplifier output signal.