Abstract: A combined optical power meter and receiver is provided in which the optical power meter retains high sensitivity and the optical receiver retains high bandwidth. A single photodiode provides current for both the optical power meter and the optical receiver. A first operational amplifier is configured as an integrating transimpedance amplifier having a current input which is referenced to a reference voltage and receives current from one port of the photodiode. A second operational amplifier is configured as a transimpedance amplifier having a current input which is referenced to ground and receives current from the other port of the photodiode. In this manner, a bias voltage is developed across the photodiode to decrease the capacitance and increase the operational speed of the receiver. A second material photodiode is provided which is shielded from the input light source is coupled to the current input of the first transimpedance amplifier.

Abstract: A thermally stabilized optical preamplifier includes a first transimpedance amplifier which receives a photosignal current from a photodiode. The gate of a GaAs device is the input to the first transimpedance amplifier, and the drain is coupled to a source of constant current. Also coupled to the drain of the GaAs device is a common base stage, and the gain of the first transimpedance amplifier is set by a resistor coupled between the input of the first transimpedance amplifier and the output of the common base stage. A current setting resistor coupled to the output of the first transimpedance amplifier converts output voltage to current, which is summed with a compensating current in a second transimpedance amplifier. The compensating current consists of a variable current generator and a thermal current generator which compensate for the current produced by the absolute value and thermal characteristics of the gate to source voltage of the input GaAs device.

Abstract: A combined electrical and optical channel for use in an oscilloscope is provided in which the vertical deflection factor is set by a single input attenutation selector switch. The electical input is passed through an attenuator. The optical input is passed through an input transimpedance amplifier having at least two gain modes and an attenuator. The output from the input attenuation selector switch is encoded to form a digital output. The attenuators for the electrical channel are driven directly by the input attenuation selector switch or by the digital output corresponding to the setting of the input attenuation selector switch. The digital output is also decoded by a logic block to generate a gain mode logic signal to switch the gain modes of the input transimpedance amplifier.