Title :
A high dynamic range CMOS variable gain filter for ADSL
Author :
Mehrmanesh, S. ; Atarodi, M.
Author_Institution :
Sharif Univ. of Technol., Tehran, Iran
Abstract :
A 3rd order, 1.1 MHz, lowpass Butterworth Gm-c filter has been combined with a low noise variable gain amplifier to form the variable gain filter (VGF). In this VGF an improved transconductor is used and a new method is used to adjust the transconductance gain for tuning application. A continuous variable gain current-to-current converter is used to tune the transconductor value. The THD of the VGF is -85 dB for 1 Vppd input signal and -50 dB for 3 Vppd input signal. VGF gain can be varied from 0 to 31 dB with 1 dB variation steps. Input referred noise is 20 nV/√(Hz) for maximum gain. All the circuits are designed based on a 0.25 μm CMOS process technology.
Keywords :
Butterworth filters; CMOS analogue integrated circuits; active filters; circuit tuning; digital subscriber lines; frequency response; harmonic distortion; low-pass filters; 0 to 31 dB; 0.25 micron; 1 to 3 V; 1.1 MHz; ADSL; CMOS; THD; continuous variable gain current-to-current converter; dynamic range; input referred noise; lowpass Butterworth Gm-c filter; transconductance gain; transconductor; variable gain amplifier; variable gain filter; Circuit noise; Circuit topology; Dynamic range; Filters; Gain; Noise figure; Resistors; Transconductance; Transconductors; Voltage;
Conference_Titel :
Circuits and Systems, 2002. ISCAS 2002. IEEE International Symposium on
Print_ISBN :
0-7803-7448-7
DOI :
10.1109/ISCAS.2002.1010439
