Operational transconductance amplifier (OTA) is one of the most significant building-blocks in integrated discret-time filters used in analog to digital converter (ADC) for Sigmadelta converter. In this paper we designed a novel design method of two-stage CMOS amplifier in AMS 0.35μm technology. P-Spice simulation results confirm the proposed OTA circuit. In fact, we achieved a gain band width (GBW) equal to 55 MHz, Cut-off frequency of 85 KHz and 57 dB gain (Av). In addition our new method allowed us to reduce settling time (S t ) to 15.6 ns and a slew rate (SR) of 0.1 V/µs at ±1.5V supply voltage. Eventually we have also succeeded in reducing the average power consumption to 1.65 mW while driving 3 pF load capacitor.
Variable-gain amplifier (VGA) is one of the basic building blocks of many communication systems. In this paper we present a novel structure of VGA with 22 db of gain range and 220 MHz of bandwidth frequency variation. This circuit combines a voltage to current (V-I) converter and two-stage CMOS amplifier to achieve programmable gain and bandwidth .The gain is varied by changing the input voltage (V in) from-1V to 0V. The maximum bandwidth is about 300 MHz. The gain can be varied from 38 dB to 60 dB in 1 dB gain steps. The overall circuit draws current from 10µA to 150µA at ±1.5V power supply. The noise figure of the system at maximum gain is 18dB, and the third-order intermodulation intercept point (IIP3) at minimum gain is-8 dBm. Simulations results with static and dynamic behaviour is presented and validated with the technology AMS 0.35µm. Eventually we have also succeeded in reducing the static power consumption to 0.5 mW.
Miwed-mode simulations are increasing& recognized as useful methods for the validation of mixedsignal circuirs before going on fabrication. HDL-A is one of the useful hardware descripbn rclnguage devoted for analog and miwed-signal ckcui&. Thk paper attempts to validate the converswn algorithm of a multi-slope se&alibrated analogto-digital converter by means of HDL-A. We will show, for the analog part of the structure, the agreement between modeling and experimental resub.
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