An extension of the op-amp concept featuring two differential inputs is presented. In a closed-loop environment this circuit forces two floating voltages to the same value, and thus has many interesting applications in the analog circuit domain. The formal description of such a circuit, its nonidealities and restrictions are given. A monolithic integration of this differential difference amplifier (DDA) in a double-poly CMOS technology and the measured characteristics are described. Many applications of this circuit, including a voltage comparator with floating inputs, a voltage inverter without resistors and an instrumentation ampli #er with only two external gain determining resistors are discussed.

Contents 1 Introduction 9 1.1 Current system description languages . . . . . . . . . . . . . . . . . 9 1.2 Formal function theory . . . . . . . . . . . . . . . . . . . . . . . . . 10 1.3 Interpretation of formal functions . . . . . . . . . . . . . . . . . . . . 11 1.4 Semantic functions . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 1.5 System semantics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 1.6 Adirectional systems . . . . . . . . . . . . . . . . . . . . . . . . . . 14 1.7 Applications of system semantics . . . . . . . . . . . . . . . . . . . . 14 1.8 The ESPRIT project FORFUN . . . . . . . . . . . . . . . . . . . . . 14 1.9 The contents of this thesis . . . . . . . . . . . . . . . . . . . . . . . . 16 2 Mathematical background 17 2.1 Overview of mathematical notation used . . . . . . . . . . . . . . . . 18 2.2 Formal function theory . . . . . . . . . . . . . . . . . . . . . . . . . 18 2.3 Formal language theory . . . . . . . . . . . . . . . . . . . . .

Matching networks are often used at the input of low noise amplifiers to match the input impedance to the source. Generally this matching results in a non-optimal noise behavior. In addition the matching network itself often generates a significant amount of noise. This paper proposes a wide-band LNA, based on double-loop negative feedback, that has an inherent matched input impedance. It offers the possibility to design and bias the input transisitor for maximum noise performance, and has the potential to increase linearity, without affecting the input impedance. An integrated HF transformer is used in one of the feedback loops and the effects of transformer non-idealities on noise behavior, input impedance and bandwidth are investigated.

In this paper, the design of linear amplifiers for current sources with very low, or voltage sources with very high impedance is discussed. In designing negative-feedback amplifiers for these sources, the loopgain is often low as a result of the source impedance, thus making it di#cult to obtain a su#ciently high bandwidth. Here, it is proposed to use CB or CC stages in front of a negative-feedback amplifier. It turns out that the use of these stages does not have to have large detrimental e#ects on noise or distortion properties, while providing a good means to achieve a higher bandwidth. Moreover, the system becomes more robust to source parameter variations. Keywords--- linear amplifiers, bandwidth optimization, structured electronic design I. Introduction In this paper, the design of linear amplifiers for current sources with a low impedance or voltage sources with a high impedance is discussed. As an example, if a negative-feedback amplifier is to be designed for a very low imp...

In this paper, a low-power adaptive low noise amplifier (LNA) is presented. The LNA is based on a bipolar cascode topology, uses inductive source degeneration and emitter area scaling to achieve noise and input-impedance matching simultaneously. The input impedance and the noise factor were simulated as function of the bias collector current and the results show that both are approximately constant over a range of half a decade of bias current, gracefully degrade when the bias current decreases, thereby saving power.

In this paper, the design strategy for a circuit synthesis program is described. Unlike other synthesis programs, the program searches in an extremely large set of possible circuits (over 1,000,000 possible circuit configurations), and is not restricted to one device technology. It uses