Wideband Operational Amplifier Research Articles

Структура и элементная база приёмо-передающего модуля для организации подводной оптической беспроводной системы передачи данных

In the paper, the results of theoretical study of a wireless optical data transmission channel, as well as experimental study of its characteristics, taking into account different configurations of the optical component base of receiving and transmitting modules, were presented. The model of the wireless underwater optical communication channel with pulse-position modulation (4 bits per symbol) of digital data traffic with 100 Mbps is proposed. The model showed that to organize a communication channel on a 10 m path, the use of an array of light-emitting diodes (LEDs) is requires (the amount is up to 20 LEDs). For this case, a sufficiently large route budget will be provided, even with additional factor that reduce the efficiency of light propagation in seawater. The LEDs were chosen to organize the data transmission channel, since they have a wide radiation pattern and allow the implementation of a relatively simple driver circuit. The required optical radiation power is realized with the use of an array of LEDs. Schematic diagrams of the LEDs driver and power supply for the receiving and transmitting modules have been designed. A measuring layout with optical transmitter and receiver blocks has been implemented. The test signal is a regular sequence of pulses with a duty cycle of 2, and a frequency of 1 MHz. In the receiving module, the signal from the output of the pin photodiode is amplified using a wideband operational amplifier. Sets of 3 pin photodiodes and 10 LEDs were selected and tests were carried out to determine options for optical components that provide the best time characteristics of the output electrical signal in terms of delay time, rising and falling edges of pulses in a wireless optical airborne communication channel. Also, measurements were done on an air path with a length of 0.25-3 m using one or two LEDs as part of the transmitting module. It has been experimentally confirmed that the organization of a communication channel with a length of up to 10 m requires about 15-20 light-emitting diodes. Further study involves the designing and testing of a driver for the LEDs array and a prototype transceiver module.

Circuit Design Modernization of Operational Amplifiers for Increasing Slew Rate of Output Voltage

To meet the existing needs of the domestic market of radio electronic equipment in high-speed wideband operational amplifiers, it was previously proposed to use the MH2XA031 master slice array containing complementary bipolar transistors, together with the developed circuits of the OAmp9 high-speed operational amplifier and the OAmp10 precision operational amplifier with unified cascades and the ability to program parameters such as current consumption, maximum output current, bandwidth, slew rate. The article discusses the increase in the performance of these operational amplifiers by reducing the parasitic collector capacitance of transistors by applying a reverse bias voltage to OAmp9 and using correction circuits in OAmp10, which made it possible to increase the output voltage slew rate by 29 % in the first case and 3.1 times in the second. The electrical circuits and the results of circuit simulation of the upgraded amplifiers, called OAmp9M, OAmp10M, are presented, which are respectively characterized by a zero offset voltage of 0.35 and 0.03 mV, a voltage gain of 2.7 · 103 and 3 · 105, the gain bandwidth product 161 and 68 MHz, output voltage slew rate 708 and 64.5 V/µs.

Sinusoidal Oscillators Operating at Frequencies Exceeding Unity-Gain Bandwidth of Operational Amplifiers

This paper proposes a novel operational amplifier (OPA) voltage-controlled oscillator (VCO) circuits on the basis of impedance converters. The VCO can operate over a frequency range exceeding unity-gain bandwidth due to the location of the tank circuit, not at the output of the OPA, but at the noninverting input. The paper presents the mathematical modeling of oscillated amplitude and start-up conditions. The simulation results confirm the theoretical achievements. The designed and simulated VCO uses an ultra-low noise wideband OPA LMH6629MF, covers a frequency band between 0.830 GHz and 1.429 GHz, and exhibits a maximum in-band total harmonic distortion (THD) of 1.7%. It has a maximum in-band phase noise of −139.3 dBc/Hz at 100 kHz offset frequency and has an outstanding value of a standard figure of merit (FoM) of −198.6 dBc/Hz. The zero-peak amplitude of output voltage is from 3.2 V to 4 V for all generated frequencies at a supply voltage of ±5 V. The fabricated prototype-oscillator based on OPA LMH6624 operates at a frequency of 583.1 MHz with a power level of 0 dBm.

Influence of ionizing radiation on the parameters of an operational amplifier based on complementary bipolar transistors

The influence of a 4 MeV energy electron flux and 60Co gamma radiation with an average energy of 1.25 MeV on the characteristics of silicon complementary bipolar transistors (BTs) and a wide-band operational amplifier (OA) has been studied. It is established that an action of FE = 3×1014 el/cm2 electron fluence causes a decay in the common–emitter current gain (s) of 61% for NPN and 66% for PNP transistors, as well as a decrease in the maximum value of the transition frequency (fT) of 12% for NPN and by 4% for PNP transistors. When the absorbed dose DG amounts to 3 Mrad, a decrease in s by 39% for NPN and by 44% for PNP transistors, and in fT of 10% for NPN and 11% for PNP transistors is observed. Despite the substantial decay in s of transistors, the OA circuitry provided the retention of the operation speed and a small decrease in the offset voltage (about 1.5 mV) in the irradiation range mentioned. The circuitries of OA cascades and the experimental characteristics of the BTs and OAs are presented.

Modeling and designing of high-gain, wide-band and fast-speed operational transconductance amplifier

Based on the analysis of the inherent limitations of conventional OTA, this paper introduces a basic strategy by combinating linear-nonlinear adaptive current mirror and local cross-pair to solve the mutual restraint between AC and DC characteristics of the circuit. In order to simplify the multi-mode complicated circuit design, an analytical model for the new OTA is proposed, which is consistent with SPICE simulation results. Under the limitation of the static current consumption, the maximum limit of the circuit performance can be predicted by the proposed model. Under the condition of 29 μA quiescent current and 30 pF load capacitance, a chip is implemented in 0.18 μm CMOS technology, and the test results show that the DC gain, GBW and slew rate achieve 73 dB, 6 MHz and 14 V/μS, respectively, and the optimal performance of DC, AC and transient can be obtained almost simultaneously.

Recent Advances on the Design of High-Gain Wideband Operational Transconductance Amplifiers

Feed-forward techniques are explored for the design of high-frequency Operational Transconductance Amplifiers (OTAs). For single-stage amplifiers, a recycling folded-cascode OTA presents twice the GBW (197.2 MHz versus 106.3 MHz) and more than twice the slew rate (231.1 V/s versus 99.3 V/s) as a conventional folded cascode OTA for the same load, power consumption, and transistor dimensions. It is demonstrated that the efficiency of the recycling folded-cascode is equivalent to that of a telescopic OTA. As for multistage amplifiers, a No-Capacitor Feed-Forward (NCFF) compensation scheme which uses a high-frequency pole-zero doublet to obtain greater than 90 dB DC gain, GBW of 325 MHz and better than phase margin is discussed. The settling-time- of the NCFF topology can be faster than that of OTAs with Miller compensation. Experimental results for the recycling folded-cascode OTA fabricated in TSMC 0.18 m CMOS, and results of the NCFF demonstrate the efficiency and feasibility of the feed-forward schemes.

An overview of feed-forward design techniques for high-gain wideband operational transconductance amplifiers

In this paper, feed-forward techniques are revised and used for the design of high-frequency operational transconductance amplifiers (OTA). For the same power consumption and similar transistor dimensions, the two- and three-path folded-cascode OTA's present both smaller settling error and faster response as compared to the typical folded-cascode topology. Also, a no-capacitor feed-forward (NCFF) compensation which uses a high-frequency pole–zero doublet to obtain high gain, high GBW and a good phase margin is discussed. The settling-time of the NCFF topology can be faster than that of OTA's with Miller compensation, even if the latter topology uses larger transconductance values. Experimental results for the multi-trajectory OTA's fabricated in the AMI 0.5 μm CMOS process demonstrate the feasibility of the feed-forward schemes.

Wide-band low-noise tunnel current measurements in laser assisted experiments

A composite current-to-voltage converter that shows a superior bandwidth and signal-to-noise ratio (bandwidth ∼50 MHz at 410 kΩ transimpedance) was designed. Two options for the input stage were tested: a high input impedance wide-band operational amplifier (OP) OPA655 (Burr–Brown) and a differential cascade which is based on the junction field effect transistors SST440 (Siliconics). By using a wideband current feedback OPA658 in the second stage the achieved bandwidth gain product is ∼10 GHz. A method for testing the performance of the preamplifier by using laser induced electron emission is described. The technique’s possibility for measurements of laser induced acoustic waves with high sensitivity and nanometer local resolution is demonstrated. For further applications the design of a wide-bandwidth, low-noise, single tunneling electron counting capable preamplifier is discussed.

A BiCMOS wideband operational amplifier with 900 MHz gain-bandwidth and 90 dB DC gain

A fully differential operational amplifier has been designed and fabricated for analog-to-digital converter application. The amplifier mainly consists of folded cascode structure with current source as output loads and common-mode feedback circuits. The technique of feed-forward compensation is used in order to improve the settling time and gain bandwidth (GBW) of this amplifier. This amplifier is integrated in 0.8 /spl mu/m BiCMOS process with an active die area of 0.1 mm/sup 2/. The DC gain of this amplifier is 90 dB. The GBW and phase margin of this amplifier is 900 MHz and 47/spl deg/, respectively. The power dissipation is minimized by using BiCMOS technology and is about 25 mW for 2 pF load capacitance.

Variable gain, zero offset, dc coupled video amplifier for microwave detector diodes

A variable gain, zero offset, dc coupled video amplifier has been developed which uses a recently introduced ±5 V operational amplifier with 1.6 GHz gain-bandwidth product. The amplifier is inexpensive and it is particularly suited for amplifying the outputs of microwave diode detectors and driving 50 Ω loads. The large input bias currents of wideband operational amplifiers increase the sensitivity of positive polarity diode detectors, but they decrease the sensitivity when a negative polarity diode detector is used at the amplifier input. To eliminate this effect, matched N-channel junction field-effect transistors (JFETs) are used to buffer the operational amplifier inputs, which reduces the input bias current to ∼1 pA. An added benefit of the JFETs is that the amplifier offset voltage is unaffected by changes in gain or source impedance. Once the offset is zeroed out, it remains zero for all gains and for any combination of diode detectors connected at the input. The maximum attainable gain-bandwidth product is somewhat lower with the JFETs (typically 400 MHz), but the amplifier operates reliably for gains up to 40–50 dB.

Integrated AlGaAs/GaAs HBT high slew-rate and wide band operational amplifier

We report the design, fabrication, and test results of a wide band and high slew-rate voltage-mode operational amplifier using AlGaAs/GaAs HBT's. To select higher carbon doping concentration is more effective in reducing base resistance, and lower emitter doping concentration possess a smaller input capacitance to improve the device speed. The HBT operational amplifier has provided 500 V//spl mu/s high slew-rate, only 8 ns setting time and about 2 GHz unity-gain frequency. Common mode rejection ratio (CMRR) values of this operational amplifier are in the order of 70 dB with a small DC input voltage offset 5 mV, and the open-loop gain is about 40 dB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Equipment, Materials and Services

The AM1435 from Datel is an ultra‐fast settling wideband operational amplifier that is directly inter‐changeable with devices having the same type number.

A Technique for Measuring the Equivalent RMS Input Noise of A/D Converters

A simple accurate technique is described for measuring the equivalent rms input noise of A/D converters. Noise can typically be measured with 10-percent accuracy in 1 s, and the method has successfully been applied to converters with up to 16 bits of resolution. The measurements are made at input voltages corresponding to the test converter's decision levels, where the effects of noise are most pronounced. A feedback loop incorporating the unit under test locates and locks onto these levels. The method utilizes a theoretical relationship between the input noise and an expected number of counts derived digitally from the feedback loop response. A low-noise wide-band operational amplifier is the only critical component required.

A wide-band operational amplifier with a new output stage and a simple frequency compensation

Innovations in circuit design have resulted in a high-performance wide band operational amplifier made by standard integrated-circuit production processes. A new class-B output circuit with very low distortion and high quiescent current stability a coupling method for differential amplifier stages incorporating the elimination of amplifier stages at high frequencies to obtain a first-order frequency response and an input stage combined with a level shift with lateral p-n-p transistors having capacitive feed forward to increase the bandwidth are used in this amplifier. A unity gain bandwidth of 50 MHz with an open-loop voltage gain of 3.10/SUP 5/ and an input bias current of 10 nA are obtained.

On a temperature stabilized wideband operational amplifier

Investigations on a wideband differential input operational amplifier are presented. A temperature stabilized input transistor pair has been utilized. An input offset voltage drift of less than 2 omegaV/°C at a power bandwidth larger than 5 MHz is obtained. The output stage is able to deliver ±10 V into 50 Ω.