Realization of Current-Mode KHN-Equivalent Biquad Using Current Follower Transconductance Amplifiers (CFTAs)

Norbert HERENCSAR  Jaroslav KOTON  Kamil VRBA 

Publication
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences  Vol.E93-A  No.10  pp.1816-1819
Publication Date: 2010/10/01
Online ISSN: 1745-1337
Print ISSN: 0916-8508
Type of Manuscript: LETTER
Category: Analog Signal Processing
Keyword: 
CFTA,  current-mode circuit,  KHN-biquad, 

Full Text: PDF

Summary: 
In this letter a new active element the Current Follower Transconductance Amplifier (CFTA) for the realization of the current-mode analog blocks is presented. The element is a combination of the Current Follower (CF) and the Balanced Output Transconductance Amplifier (BOTA). Possible internal structure of the CFTA is presented. The usage of the new active element is shown on the design of the Kerwin-Huelsman-Newcomb (KHN) structure working in the current mode. The frequency filter using the CFTA elements has been designed using the signal-flow graphs. The circuit structure employs three CFTA elements and two grounded passive elements. The filter enables realizing not only the basic functions as the low- (LP), band- (BP) and high-pass (HP) but also the notch and all-pass (AP) filter. The advantage of the structure presented is that the outputs of the filter are at high impedance and hence it is not necessary to use other auxiliary active elements. The properties of the filter proposed were verified by sensitivity and AC analyses in the PSPICE program.