Sharif Digital Repository

A 3rd order, 1.1 MHz, lowpass butterworth Gm-c filter has been combined with a low noise Variable Gain Amplifier to form the Variable Gain Filter (VGF). In this VGF an improved transconductor is used and a new method is used to adjust the transconductance gain for tuning application. A continuous variable gain current-to-current converter is used to tune the transconductor value. The THD of the VGF is -85 dB for 1 Vppd input signal and -50 dB for 3 Vppd input signal. VGF gain can be varied from 0 to 31 dB with 1 dB variation steps. Input referred noise is 20 nV/√Hz for maximum gain. All the circuits are designed based on a 0.25 μm CMOS process technology  

A 12 bit 25 MS/S pipelined analog-to-digital (A/D) converter was designed and simulated using 0.35 μm CMOS technology. The proposed new high speed class AB opamp makes it possible to achieve requirements of 12 bit resolution and settling in 20 ns within 0.05% accuracy. However, pipeline ADCs are tolerant to comparator's offset, but using dynamic comparators, power dissipation can be reduced. So a dynamic comparator is designed which is more power efficient. Total power dissipation is about 76 mW from a single 3 V supply, where INL and DNL are 0.8 LSB and 0.6 LSB respectively. A SNDR of 70.1 dB is achieved. © 2003 IEEE  

A 4th order, 5 MHz, lowpass Butterworth Gm-c filter has been combined with a low noise low-voltage amplifier to form a lowpass filter for video applications. In this filter an improved transconductor and a powerful method is used to adjust the transconductance gain for tuning application. A continuous variable gain current-to-current converter is used to tune the transconductor value. The THD of the filter is -77 dB for 1 Vppd input signal. Input referred noise is 40 nV/√Hz in the worst case. All the circuits are designed based on a 0.25 μm CMOS process technology with a single 1.8 V supply. © 2002 IEEE  

The transformer-feedback (TRFB) interstage bandwidth enhancement technique for broadband multistage amplifiers is presented. Theory of the TRFB bandwidth enhancement and the design conditions for maximum bandwidth, maximally flat gain, and maximally flat group delay are provided. It is shown that the TRFB bandwidth enhancement can provide higher bandwidth compared to the conventional techniques based on reactive impedance matching networks. A three-stage low-noise amplifier (LNA) monolithic microwave integrated circuit with the TRFB between its consecutive stages is designed and implemented in a 0.1-μ m GaAs pHEMT process. The TRFB is realized by coupling between the drain bias lines of... 

Design techniques to enhance bandwidth and linearity of broadband multistage low-noise amplifiers (LNAs) are presented. A feedback amplifier circuit is proposed to compensate for transistor gain roll-off with frequency in other amplifier stages and extend overall bandwidth. Moreover, a transistor width tapering in a multistage LNA is applied to improve linearity. These techniques are adopted in a three-stage monolithic microwave integrated circuit (MMIC) LNA implemented in a 0.1-μm GaAs pHEMT process. The LNA features 18-43 GHz bandwidth, 21.6 dB average gain, and 1.8-2.7 noise figure (NF). It exhibits output 1-dB compression point of 11.5 dBm at 30 GHz and consumes 70 mA bias current from a...