Active and Passive Electronic Components

Volume 2013 (2013), Article ID 971936, 5 pages

http://dx.doi.org/10.1155/2013/971936

Research Article

Single-Resistance-Controlled Sinusoidal Oscillator Using Single VD-DIBA

K. L. Pushkar,¹ D. R. Bhaskar,² and Dinesh Prasad²

¹Department of Electronics and Communication Engineering, Maharaja Agrasen Institute of Technology, Rohini, New Delhi 110086, India

²Department of Electronics and Communication Engineering, F/O Engineering and Technology, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India

Received 17 January 2013; Accepted 27 March 2013

Academic Editor: Ali Umit Keskin

Copyright © 2013 K. L. Pushkar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

This paper presents a new single-resistance-controlled sinusoidal oscillator (SRCO). The proposed oscillator employs only one voltage differencing differential input buffered amplifier (VD-DIBA), two resistors, and two grounded capacitors. The proposed configuration offers the following advantageous features: (i) independent control of condition of oscillation and frequency of oscillation, (ii) low active and passive sensitivities, and (iii) a very good frequency stability. The validity of the proposed SRCO has been established by SPICE simulations using 0.35 μm MIETEC technology.

1. Introduction

Realisation of oscillators and active filters has become important research area in analog circuit design. Recently, various modern active building blocks have been introduced in [1], and VD-DIBA is one of them which is emerging as a very flexible and versatile building block for analog signal processing and has been used earlier for realizing a number of functions. Single-resistance-controlled sinusoidal oscillators (SRCOs) play an important role in control systems, signal processing, communication, and instrumentation and measurement systems [2–4]. SRCOs employing different active building blocks have attracted considerable attention of the researchers due to their several advantages over traditional op-amp-based SRCOs; see [5–15] and the references cited therein. The applications, advantages, and usefulness of VD-DIBA have now been recognised in the realisation of first-order all-pass filter, in simulation of inductors and in the realisation of sinusoidal oscillator [16–18]. However, to the best of the knowledge and belief of the authors, none of the SRCOs using single VD-DIBA has yet been presented in the literature so far. Therefore, the purpose of this paper is to present a new SRCO using a single VD-DIBA along with a bare minimum number of four passive components. The proposed configuration offers (i) independent control of condition of oscillation and frequency of oscillation, (ii) low active and passive sensitivities, and (iii) a very good frequency stability. The workability of the proposed SRCO has been established by SPICE simulations using 0.35 μm MIETEC technology.

2. New Oscillator Configuration

The schematic symbol and behavioral model of the VD-DIBA are shown in Figures 1(a) and 1(b), respectively. The model includes two controlled sources: the current source controlled by differential voltage , with the transconductance , and the voltage source controlled by differential voltage , with the unity voltage gain. The VD-DIBA can be described by the following set of equations:

A routine circuit analysis of Figure 2 yields the following characteristic equation:

Thus, the condition of oscillation (CO) and frequency of oscillation (FO) are given by

Therefore, it is seen that FO is independently controllable by resistor and CO is controlled by .

(a)

(b)

Figure 1: (a) Schematic symbol and (b) behavioural model of VD-DIBA.

Figure 2: The proposed configuration.

3. Frequency Stability Analysis

Frequency stability may be considered to be an important figure of merit of an oscillator. The frequency stability factor is defined as , where is the normalized frequency, and represents the phase function of the open loop transfer function of the oscillator circuit, with ,  ,  , and ;   for the proposed SRCO is found to be

Thus, for larger values of , the oscillator enjoys a very good frequency stability.

4. Nonideal Analysis and Sensitivity Performance

Let and denote the parasitic resistance and parasitic capacitance of the -terminal of the VD-DIBA. Taking the nonidealities into account, namely, the voltage of  -terminal , where    and    denote the voltage tracking errors of -terminal and -terminal of the VD-DIBA, respectively, then the expressions for CO and FO become

The left-hand side of (3) with the component values shown in Section 4 turns out to be −0.812 which is in accordance with (3) (<0). On the other hand, when left-hand side of (6) is calculated using the components and parasitic values in Section 4, it turns out to be −0.7992. It is therefore seen that both values are quite close from these numerical examples; it can be inferred that by considering , and   , , (6) becomes which shows that (6) is almost the same as (3).

Its active and passive sensitivities can be found as

In the ideal case, the various sensitivities of FO with respect to ,  ,  , and are found to be

Considering the typical values of various parasitic, for example,  pF,  kΩ, and along with  nF,   kΩ, and  kΩ, the various sensitivities are found to be  ,  ,  ,  ,  , ,  , and    which are all low.

5. Simulation Results

To confirm theoretical analysis, the proposed SRCO was simulated using CMOS VD-DIBA (as shown in Figure 3). The passive elements were selected as  nF,  KΩ, and  KΩ. The transconductance of VD-DIBA was controlled by bias voltage . PSPICE-generated output waveforms indicating transient and steady state responses are shown in Figures 4(a) and 4(b), respectively. These results, thus, confirm the validity of the proposed configuration. Figure 5 shows the output spectrum, where the total harmonic distortion (THD) is found to be 2.77%. Figure 6 shows the variation of frequency with resistance . A comparison with other previously known SRCOs using different active building blocks has been given in Table 2.

Figure 3: Proposed CMOS implementation of VD-DIBA;  V,   V,  V, and  V.

(a)

(b)

Figure 4: (a) Transient output waveform. (b) Steady state response of the output.

Figure 5: Simulation result of the output spectrum.

Figure 6: Variation of frequency with resistance .

The CMOS VD-DIBA is implemented using 0.35 μm MIETEC real transistor model which is listed in Box 1.

.MODEL N NMOS (LEVEL = 3 TOX =  NSUB =  GAMMA = 0.5827871 PHI = 0.7 VTO = 0.5445549

DELTA = 0 UO = 436.256147 ETA = 0 THETA = 0.1749684 KP =  VMAX =  KAPPA = 0.2574081

RSH = 0.0559398 NFS =  TPG = 1 XJ =  LD =  WD =   CGDO =

CGSO =  CGBO = 1 CJ =  PB = 0.9758533 MJ = 0.3448504 CJSW =

MJSW = 0.3508721)

.MODEL P PMOS (LEVEL = 3 TOX =  NSUB =  GAMMA = 0.4083894 PHI = 0.7 VTO = −0.7140674

DELTA = 0 UO = 212.2319801 ETA =  THETA = 0.2020774 KP =  VMAX =

KAPPA = 1.5 RSH = 30.0712458 NFS =  TPG =  XJ =  LD =  WD =

CGDO =  CGSO =  CGBO =  CJ =  PB = 0.8152753 MJ = 0.5 

CJSW =  MJSW = 0.5)

Box 1

Aspect ratios of transistors used in Figure 3 are given in Table 1.

Table 1

Transistor
W/L (µm)

M₁–M₆
14/1

M₇–M₉
14/0.35

M₁₀–M₁₈
4/1

M₁₉–M₂₂
7/0.35

Table 2

Reference
Active component(s)
Grounded

capacitors
Floating capacitors
Resistors
CO and FO independently controllable

[5]
1
1
1
3
Yes

[6]
1
1
1
3
Yes

[7]
2
2
0
3
Yes

[8]
1
1
1
3
Yes

[9]
1
2
0
4
No

[10]
1
2
0
3
Yes

[11]
1
2
0
3/2
Yes

[12]
1
1 (virtually grounded)
1
3
Yes (only in second topology of Table 1)

[13]
1
1 (virtually grounded)
1
3
No

[14]
1
1
1
2
Yes

[18]
2
2
0
1
Yes

[15]
1
2
0
2
Yes

Proposed
1
2
0
2
Yes

6. Conclusions

A new application of a recently introduced VD-DIBA in the realisation of SRCO has been proposed. The proposed configuration employs a minimum possible number of passive elements (namely, two resistors and two grounded capacitors) and yet offers independent control of FO through the resistor and CO through the transconductance (hence, the circuit enjoys the electronic control of CO), low active and passive sensitivities, and a very good frequency stability. This paper thus added a new application circuit to the existing repertoire of VD-DIBA-based application circuits.

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