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Monolithic Low Noise Wide Band Amplifier

IP.com Disclosure Number: IPCOM000079835D
Original Publication Date: 1973-Sep-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Liu, CC: AUTHOR

Abstract

A monolithic multiple-input low-noise wide-band amplifier circuit consists of emitter-coupled differential transistor pairs 10A-F, with their respective collectors connected. Magnetic heads 12A-F are connected to each of the amplifier inputs. Only one channel is selected at any one given time by a selection means, which steers a current source to the emitter circuit of the selected transistor pair.

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Monolithic Low Noise Wide Band Amplifier

A monolithic multiple-input low-noise wide-band amplifier circuit consists of emitter-coupled differential transistor pairs 10A-F, with their respective collectors connected. Magnetic heads 12A-F are connected to each of the amplifier inputs. Only one channel is selected at any one given time by a selection means, which steers a current source to the emitter circuit of the selected transistor pair.

In Fig. 1, the input transistor pairs 10A-F are conventionally of an interdigitated design to meet the low-noise requirement, and have large collector area and, consequently, large collector capacitance. This excessive large capacitance severely degrades the bandwidth performance of the amplifier.

Instead, a common-base transistor array 14A-F made of devices with relatively small geometry and, consequently, small capacitance is used. Therefore, the apparent capacitance at nodes 16 and 18 is reduced. In addition, the common-base transistor array provides a low-impedance collector load to the selected input emitter-coupled differential pair. The voltage gain of the input pair is about unity, therefore, the Miller capacitance is reduced and the bandwidth is improved. An additional common-base differential pair 20A, 20B is introduced for further band-width enhancement. In this unique arrangement, the noise contribution by the added common-base transistor array and the common-base differential pair is an insignificant amount.

Fig. 2...