Self generating square/triangular wave and pulse width modulator using a single MO-CCCDTA

Abstract

A self-generating square/triangular wave and pulse width modulator (PWM) using multiple output current controlled current differencing transconductance amplifier (MO-CCCDTA) is presented. To obtain all the three functions simultaneously from the same topology, the MO-CCCDTA is modified a little bit. The characterisation of the modified MO-CCCDTA structure shows that the parasitic resistances at input terminals (n and p) can be varied via bias current. The maximum useful frequency range is found to be 635 MHz, which is higher than the available literature. The waveform generator and PWM circuit use only one MO-CCCDTA, one grounded capacitor and no resistor; hence suitable for IC implementation. The duty cycle of proposed pulse width modulation can be tuned by bias current of MO-CCCDTA over a wide range. The performances of the proposed block and its applications (square/triangular/PWM) are verified by PSPICE simulation using TSMC 0.35 µm technology. The power consumption is about 1.12 mW. To verify experimentally, a prototype of MO-CCCDTA has been made using commercially available ICs (AD844AN and CA3080) on printed circuit board. The simulation and experimental results verify theoretical proposition well. Monte carlo simulation is carried out, which proves satisfactory performance of the proposed circuit against mismatches. The performance of the proposed circuit is also verified through pre-layout and post-layout simulation results. The required chip area is only 22.415 × 14.6 µm2.