Abstract: A sampled-data-integrating front end is employed to convert an optical signal to a digital electrical signal. The front end includes a photodetector and an array of parallel conversion circuits, each including an activation switch, a charge amplifier and an Analog to Digital Converter (“ADC”). The charge amplifier includes a reset switch, a capacitor, and an amplifier. The resent switch is operable to discharge the capacitor. The capacitor is operable to charge to the voltage of a signal charge when the activation switch is closed, and to hold that voltage after the activation switch is opened. The amplifier is operable to provide current at the voltage across the capacitor for a period sufficient to enable the ADC to obtain an accurate sample. The parallel conversion circuits are time-interleaved to provide a selected resolution in the digital electrical representation of the optical signal.

Abstract: A current mirror circuit comprises first and second resistors for conducting first and second reference currents dependent upon a supply voltage, and first and second current mirrors coupled to the first and second resistors, the second resistor being in series with a voltage reference. The second current mirror mirrors the second reference current, and its mirrored current output is subtracted from the first reference current, the difference current being mirrored by the first current mirror to produce a controlled output current. The circuit can be arranged so that the controlled output current is independent of changes of the supply voltage, or, optionally with further current mirrors and voltage references, so that the controlled output current has a desired relationship with the supply voltage.