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A new dual-input differential input active integrator using a current differencing buffered amplifier (CDBA) is proposed. A multiplier element is appropriately used in the circuit whose control voltage (

With the advent of the CDBA building block [

The ICL-8013 device is a four-quadrant analog multiplier whose output is proportional to the electronic product of two input voltage signals with a transmission constant

Albeit various CDBA-based active filters/oscillators [

The proposed circuit is shown in Figure

Voltage (

We therefore get the realisability conditions for a true differential integrator, putting

With a nonideal CDBA device, these design equations would alter. The device imperfections may be expressed in terms of some port mismatch ratios [

By Reanalysis assuming finite

The realisability conditions for a true differential integrator now modify to

The active

In this analysis, we neglected the parasitic series resistance (

Inspection of (

The quadrature oscillator finds various applications in SSB modulators and spectral phase measurements: its functional capabilities are further enhanced if electronic tuning property can be incorporated. We design a VCQO using the proposed integrator in a two integrator loop, each being used single ended, one inverting and the other in noninverting mode, that is, from (

With identical integrator, the oscillation frequency would be

Ref. | Electronic tunability | ||

reported | |||

[ | No | 0.02 | |

[ | No | 0.01 | |

[ | No | 0.02 | |

Proposed | Yes | 1.02 |

Both the integrator and VCQO functions have been tested with PSPICE macromodel simulation [

Experimental results.

Integrator response with square wave excitation of

VCQO-tuning characteristics with

VCQO wave-response with build-up feature tuned for

Nyquist plot of loop function

Frequency spectrum of the loop-function

We tested the frequency response of the integrator with antiphase input sinusoid signals and observed the phase error of about 5.5° at 1 MHz. The CMRR had been measured to be 96 dB with sinusoid excitation. It may be seen that the select-frequency was reported in the range of a maximum of 200 KHz in the earlier circuits [

In order to examine the tuning error in

Tuning error and THD measured at three different tuning frequencies.

Curve | Tuned frequency | Tuning error | THD | ||

(MHz) | (MHz) | (%) | (%) | ||

A | 1.00 | 1.020 | 0.020 | 2.00 | 2.1 |

B | 0.72 | 0.727 | 0.007 | 0.97 | 1.8 |

C | 0.50 | 0.498 | 0.002 | 0.40 | 1.5 |

A new single CDBA-based differential integrator with a multiplier element in the circuit loop is presented for obtaining electronic tunability. Subsequently, a double integrator type VCQO had been designed and tested in a frequency range of 150 KHz–1 MHz with suitable design. Albeit other electronically tuned active realisations were reported recently in relatively lower frequency-range using CFA [