An Electronically Adjustable Waveform Generator

Abstract

A novel electronically adjustable square/triangular waveform generator has been introduced in this paper. The proposed circuit employs one active element, the multi-output current-controlled current conveyor transconductance amplifier, and one passive component grounded capacitor only. The resistorless realization of the presented generator provides a good advantage in terms of integrated circuit fabrication. In the offered circuit, the frequency and amplitude of the output square wave are electronically tunable by means of relevant bias currents. Additionally, the upper and lower threshold levels are electronically controllable by the respective bias current. On the contrary, electronically adjusting of the duty cycle of output waveform is possible via the external DC current. The generator circuit is simulated with TSMC 0.18[Formula: see text][Formula: see text]m technology parameters and SPICE. Moreover, the introduced circuit is implemented by using commercially available active devices and thus it is also verified experimentally.

Mathematical Expressions Useful for Tunable Properties of Simple Square Wave Generators

“…They provide a single electronically adjustable parameter such as operational transconductance amplifiers (OTA) [2,3]. The development continued with improvement of the features of these active elements and by introducing the adjustable elements with the capability of setting several parameters for driving of parameters of their applications in generators [6][7][8][9]11,12,[14][15][16][17][18][19][20][21][22][23][24][25][26]. However, some of these active elements are hypothetical only.…”

“…Their structures are usually constructed from individual transistor models and, then, final application is verified only by simulations with such structures [5][6][7][8]10,14,19,20,23,25]. Another possibility is to create an active device as so-called behavioral model consisting of several off-the-shelf commercially available standard devices [11,12,17,18,[20][21][22]24,26]. High complexity of such structures is a key disadvantage in this case (5 IC packages or more are required [11,12,17,18,20]).…”

“…We compared solutions and came to the following conclusions: (a) Very low number of solutions use DC voltage as driving force [9,12,[14][15][16]25] for tuning or adjustment of additional parameters; (b) Most circuits employ DC current as a driving force [4][5][6][7][8]10,11,[17][18][19][20][21][22][23][24]26]; (c) Only one generator was designed with completely integrated active circuitry [9]; (d) The number of active elements (without consideration of "complex behavior models") is acceptable in all cases (2-3) but number of passive elements can be very high [9]; and (e) The ratio of the frequency range vs. the driving parameter range (evaluated as figure of merit-FOM in Table 1) is quite low (<0.8) in many of the reported results [5][6][7][8][9][10][12][13][14]16,[19][20][21]23,24]. There are also solutions with excellent features for a wideband tuning [11,15].…”