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Method for symmetrical loading for differential amplifiers with single-ended excitation

IP.com Disclosure Number: IPCOM000010803D
Publication Date: 2003-Jan-22
Document File: 4 page(s) / 68K

Publishing Venue

The IP.com Prior Art Database

Abstract

Disclosed is a method for symmetrical loading for differential amplifiers with single-ended excitation. Benefits include improved high-frequency performance, improved design flexibility, and improved reliability.

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Method for symmetrical loading for differential amplifiers with single-ended excitation

Disclosed is a method for symmetrical loading for differential amplifiers with single-ended excitation. Benefits include improved high-frequency performance, improved design flexibility, and improved reliability.

Background

        � � � � � Differential circuits are preferred over unbalanced single-ended circuits because of their higher power supply rejection ratio, lesser effects by parasitic power supply wire inductance, and lesser injection of noise to the substrate. Differential implementation is the preferred implementation for higher bit rate amplifiers (Bit rate >2.5 Gb/s). In some cases, such as trans-impedance amplifiers (TIAs), the amplifiers are conventionally excited single ended (due to the availability of only one photo detector in the optical link). For optimal performance, the design must ensure that both of the inputs to the differential pairs load equally. For example, the conventional implementation requires VP and VN input pads, plus three ground (GND) pads for differential pairs with single-ended excitation (see Figure 1).

General description

� � � � � The disclosed method is symmetrical loading for differential amplifiers with single-ended excitation, such as the TIAs in optical communication systems. This architecture forms the basis for a high-performance (such as 40Gb/s) TIA for use with chipsets containing differential amplifiers and physical media dependent chipsets.

Advantages

        � � � � � The disclosed method provides advantages, including:

•        � � � � Improved high-frequency performance due to symmetrical loading

•        � � � � Improved design flexibility due to making the implementation of differential c...