A DC-to-2.3-GHz Amplifier Using an 'Embedding' Scheme

This paper describes a novel circuit technique for providing broadband amplifier gain response from dc to extremely high frequencies. The technique provides this wide spectrum response without compromising either the hf response or the dc stability. This performance is obtained by "embedding" a parameter-optimized hf amplifier within a dc gain-defining circuit, and providing means for ensuring a smooth transition between the low-frequency to high-frequency operating modes. This technique avoids the compromise of hf performance which is frequently present in direct coupled amplifiers.1,2 Amplifiers with response to dc are frequently required in communication systems employing a baseband Pulse Code Modulation (PCM) type encoding scheme where the entropy of the information signal is unknown. Because of the simplicity afforded by binary PCM, its use has been adopted in many optical systems.3 4 In such cases, the channel information rate is restricted mainly by the bandwidth of the electronic driving circuits. The economics of noncoherent optical systems again dictate the use of extremely broadband amplifiers and, if the system simplicity is not to suffer, 5 a gain response to dc is required. Such systems should benefit from an hf optimized amplifier providing gain to dc. A particular realization of the embedding technique is described in this paper which may find use in such systems. This realization 53