New Double Current Controlled CFA (DCC–CFA) Based Voltage–Mode Oscillator with Independent Electronic Control of Oscillation Condition and Frequency

Abstract

In this paper, a new electronically tunable quadrature oscillator (ETQO) based on two modified versions of current feedback amplifiers (CFAs), the so called double current controlled CFA (DCC-CFAs) is presented. The frequency of oscillation (FO) of the proposed voltage-mode (VM) ETQO is electronically adjustable by current gain or by varying the intrinsic resistance of the X terminal of the active element used. The condition of oscillation (CO) is adjustable by current gain independently with respect to frequency of oscillation. Simultaneous control of current gain and intrinsic resistance allows linear control of FO and provides extension of frequency tuning range. In the proposed circuit all the capacitors are grounded. The use of only grounded capacitors makes the proposed circuit ideal for integrated circuit implementation. The presented active element realized by using BiCMOS technology and the behavior of proposed circuit are discussed in details. The theoretical results are verified by SPICE simulations based on CMOS ON-Semi C5 0.5 µ m and bipolar ultra high frequency transistor arrays Intersil HFA 3096 process parameters.

Quadrature oscillators using two CFOAs and four passive components

“…It should be noted that if any automatic gain control circuit was implemented to oscillators, an interesting solution of controllable oscillator was introduced by Sotner et al in [13]. However, that solution is easily replaced by the proposed automatic amplitude gain control circuit.…”

“…A quadrature oscillator is used because the circuit simultaneously provides two sinusoids with 90°phase difference for a variety of applications, such as in telecommunications for quadrature mixers, in single-sideband generators, in direct-conversion receivers, or in vector generators or selective voltmeters for measurement purposes [3]. In the last two decades on the realization of voltage-mode oscillators, an application of current-feedback operational amplifier (CFOA) [3,4,5,6,7,8,9,10,11,12], double current controlled current feedback amplifier (DCC-CFA) [13], currentcontrolled current feedback amplifier (CC-CFA) [14], differential voltage current conveyor transconductance amplifier (DVCCTA) [15], differential-input buffered and transconductance amplifier (DBTA) [16], and second-generation conveyor (CCII) [17] have received considerable attention. Moreover, the four terminal CFOA, particularly the commercial available integrated circuit (IC) type AD844 providing an accessible compensation pin, has received prominent attention [3,4,5,6,7,8,9,10,11,12].…”

Study of Small-signal Model of Simple CMOS Amplifier with Instability Compensation of Positive Feedback Loop

“…(for C m = 10 pF) creates 20 dB/dec slope of the magnitude after the first pole (from the left side), then stabilization to the horizontal slope by zero (0 dB/dec) and again fall of the trace (40 dB/dec) after the dominant pole frequency (complex conjugated). It is typical for pole and zero foregoing the first (dominant) pole given approximately by equations (6), (14) or (17) …”

“…We can discuss methods like transconductance (g m ) control [1], [2] intrinsic current input resistance control (R x ) [1], [3] current gain control (B) [4][5][6][7][8], voltage gain control (A) [9], and their combinations [10][11][12][13][14].…”

First–Order Transfer Sections with Reconnection–Less Electronically Reconfigurable High–Pass, All–Pass and Direct Transfer Character

“…Utilization of the adjustable voltage gain (A) is also very useful in many cases, but complexity of active elements is worse [12] than basic structures utilizing g m or R x control [2,3]. Design of active elements in combination of several (at least two) types of control in frame of one active element is one of today's trends [13][14][15][16][17][18][19].…”