Microwave Active Filter using Finite Gain Amplifier

A Sallen and Key Active Filter Using SiGe BiCMOS Technology

“…This method has the advantage of fixing the amplifier gain by a resistive divider ratio. In this philosophy, we previously proposed, for a FET technology, a simpler and original method where the differential amplifier is replaced by a single transistor [6,8]. In this paper, we transpose this structure concept to a bipolar technology.…”

“…We showed previously [6] that equality of two resistances and two capacitances constitute the best compromise for low sensitivity. Therefore, the topology used [6,8] has R2=R4=R and C3=C4=C and:…”

A 1.3‐GHz SiGe active filter using a finite‐gain amplifier

“…The bandpass filter topology [4] is presented in Figure 1. The element values are fixed by the central frequency and Q-factor choice.…”

“…We showed previously [5] that equality of two resistances and two capacitances constitute the best compromise for low sensitivity. Therefore, the topology we use [4,5] has R 2 ϭ R 4 ϭ R and C 3 ϭ C 4 ϭ C. The central frequency f 0 and the Q factor are given by…”

“…H. Suwaki et al [6] proposed a derivative method called a "unity coupler," using a differential amplifier with two feedback loops. In this design, we use only one feedback loop [4]. Its functional and electrical schematics are shown in Figures 2 and 3.…”