Monolithic Operational Amplifier Research Articles

Modeling and Simulation of Monolithic Single-Supply Power Operational Amplifiers

In this paper a simple PSpice (Personal Simulation Program with Integrated Circuit Emphasis) macro-model was developed, and verified for monolithic power operational amplifiers operated with a single-supply voltage. The proposed macro-model is developed using simplification and build-up techniques for macro-modeling of operational amplifiers and simulates the basic static and dynamic characteristics, including input impedance, small-signal frequency responses at various voltage gains, output power versus supply voltage, slew-rate-limiting, voltage limiting, output offset voltage versus supply voltage ripples, and output resistance. Furthermore, the macro-model also takes into account the ground reference voltage in the amplifier at a single power supply voltage. The model is implemented as a hierarchical structure suitable for the PSpice circuit simulation platform. The sub-circuit is built using standard PSpice components and analog behavioral modeling blocks. The accuracy of the model is verified by extracting the model parameters for single-supply power operational amplifier TDA2005 from ST Microelectronics as example. The effectiveness of the model is validated by comparing the simulation results of the electrical parameters with the corresponding measured values obtained by experimental testing of sample circuits. The comparative analysis shows that the relative error of the modeled large-signal parameters is less than 15%. Moreover, an error of 15% is quite acceptable, considering the technological tolerances of the electrical parameters for this type of analog ICs.

High Sensitivity Very Low Frequency Receiver for Earthquake Data Acquisition

A high sensitivity very low frequency (VLF) receiver is developed based on AD744 monolithic operational amplifier (Op-Amp) for earthquake data acquisition. In research related natural phenomena such as atmospheric noise, lightning and earthquake, a VLF receiver particularly with high sensitivity is utterly required due to the low power of VLF wave signals received by the antenna. The developed receiver is intended to have high sensitivity reception for the signals in frequency range of 10-30 kHz allocated for earthquake observation. The VLF receiver which is portably designed is also equipped with an output port connectable to the soundcard of personal computer for further data acquisition. After obtaining the optimum design, the hardware realization is implemented on a printed circuit board (PCB) for experimental characterization. It shows that the sensitivity of realized VLF receiver is almost linear in the predefined frequency range for the input signals lower than -12dBm and to be quadratic for the higher level input signals.

Op amp combining precision, high speed, and high output current drive for +or-5-V power supply operation

A monolithic operational amplifier designed for +or-5-V power supply operation is described. Precision DC performance includes 100-million V/V open-loop gain, +or-25- mu V maximum input offset voltage, +or-40-nA maximum input bias current, and 2.4-nV/ square root Hz (at 1 kHz) input voltage noise. AC performance includes 9-V/ mu s slew rate, 17-MHz bandwidth, and 1- mu s settling time to 0.1%; all are measured at unity gain. The op amp is capable of directly driving into a 50- Omega load with up to +or-80 mA of output drive current. A novel input bias current cancellation circuit achieves the low input bias current while maintaining a +or-3.5-V minimum common-mode input voltage range. A novel output short-circuit protection circuit was developed. It provides good current limiting while allowing an output voltage swing of +or-4 V. A novel input offset voltage trimming scheme using laser link cutting is introduced which consumes minimum die area while providing a +or-10- mu V trim solution (+or-3-mV trimming range) and excellent long-term stability. >

Design and fabrication of a GaAs monolithic operational amplifier

The design and fabrication of the GaAs monolithic operational amplifier are described. The DC gain and frequency characteristics are discussed in detail using an equivalent circuit. The experimentally fabricated chip exhibited a unity-gain frequency of 150 MHz, an open-loop gain of 48 dB, and a common-mode rejection ratio of 63 dB. The amplifier has wide applications in high-speed D/A (digital-to-analog) converter circuits and switched-capacitor filters for video signals.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Design techniques for improving the HF response of a monolithic JFET operational amplifier

Bandwidth limitations of an operational amplifier are explored in relation to the second-order frequency response caused by the output follower's inductive emitter impedance when driving capacitive loads or by the local AC feedback associated with the Miller integration function. The substrate p-n-p follower is shown to seriously degrade the bandwidth in the sink mode due to its low /spl omega//SUB /spl tau//. New design techniques are discussed which use the integration capacitor to provide local AC feedback around a new all-n-p-n transistor output stage. This reduces both the open-loop distortion and the quiescent output resistance for a given quiescent current. This also maximizes the lower limit of the inductive frequency range in the sink mode to improve the second-order frequency responses when driving capacitive loads. The multipole local AC feedback loop (Miller loop) is analyzed, and a method of compensation is described which uses pole splitting and feedforward techniques within the Miller loop. As a result, a general-purpose monolithic p-channel JFET quad operational amplifier has been fabricated with standard low-cost technology; the amplifier achieves a 10-MHz bandwidth and a 45-V//spl mu/s slew rate, while consuming only 2.1 mA/amplifier.

Amplifier techniques for combining low noise, precision, and high-speed performance

A monolithic operational amplifier is presented which optimizes voltage noise both in the audio frequency band, and in the low frequency instrumentation range. In addition, the design demonstrates that the requirements for low noise do not necessitate compromising the specifications in other respects. Techniques are set forth for combining low noise with high-speed and precision performance for the first time in a monolithic amplifier. Achieved results are: 3 nV//spl radic/Hz white noise, 80 nV/SUB p-p/ noise from 0.1 to 10 Hz, 17 V//spl mu/s slew rate, 63 MHz gain-bandwidth product, 10 /spl mu/V offset voltage, 0.2 /spl mu/V//spl deg/C drift with temperature, 0.2 /spl mu/V/month drift with time, and a voltage gain of two million.

A temperature-stabilized programmable operational amplifier for active-R filters

A monolithic operational amplifier circuit, has been designed whose gain and bandwidth are virtually independent of temperature. Defined accurately by ratios of external resistances, the gain and 3 dB cutoff frequency are controllable from 40 dB to l00 dB and 15 Hz. to 1 kHz respectively. Temperature stability better than 100 p.p.m./°C has been measured.

Micro-Electronic Circuit Design with Integrated Components

This paper gives a review of the more significant developments in the linear micro-electronic circuit design, which are relevant to economically viable manufacture. A succinct account of the stat-of-the-art silicon monolithic operational amplifier and active-RC filter designs are presented. An evaluation of these design approaches leads to the conclusion that thick-film hybrids with plastics and organic conductors might be more suited to economic manufacture of integrated circuits whose functions are defined for specific application and which are not required in large number.

A High Quality Controlled Current Source

A technique for realizing a high-quality controlled current source is described. A monolithic operational amplifier is used as the main building block, and a modified current mirror is used to recover the signal current from the power supply leads of the amplifier. The proposed mirror exhibits low input resistance, which reduces errors due to the noninfinite power-supply rejection characteristics of the amplifier, and a current-splitting network allows the realization of output impedances in the range of tens of megohms using standard components. The entire circuit operates in a class-AB mode for high drive capability with low values of quiescent current. A simple application is included to show that a voltage amplifier can readily be constructed which exhibits a 3-dB gain-bandwidth product forty times larger than the gain-bandwidth product of the operational amplifier used. Detailed experimental results are included to verify predicted frequency response and gain characteristics.

Fault Protection of Monolithic Audio Power Amplifiers in Severe Environments

Monolithic power operational amplifiers used in automotive AM-FM stereo receivers require protective mechanisms to assure performance in severe environments. Such protective mechanisms were developed and incorporated in an audio module after the identification of five major fault categories. The module, containing two operational amplifiers to meet radio power requirements, has seven reference comparators along with the necessary output control circuitry on a single silicon die. The comparators not only sense excess voltage on the power source, current, and temperature extremes but output load faults as well. A discussion of the environment, fault categories, control requirements, and fault detection means used to obtain the objectives follows.

Computer simulation of integrated circuits in the presence of electrothermal interaction

A computer program which predicts the DC and transient performance of monolithic integrated circuits in the presence of electrothermal interactions on the integrated circuit die is described. The thermal modeling of the die/package structure and the numerical analysis procedure is discussed. Experimental and simulation results are compared for monolithic operational amplifiers, voltage regulators, and a temperature-stabilized voltage reference.

Monolithic operational amplifier design with improved HF behaviour

The design of a monolithic operational amplifier, which combines a large bandwidth and a high output current, is described. The output stage is equipped with n-p-n transistors only, biased in class-AB by an internal common-mode feedback loop. The intermediate stage consists of a unity-current-gain split-frequency-band voltage level shift. An integrated version, intended for driving 50-/spl Omega/ coaxial line systems, achieves a bandwidth of 25 MHz and 100-mA output current. The principle described provides the possibility for achieving higher output currents.

On some aspects of the high-frequency performance of operational amplifiers and current-to-voltage converters

The standard monolithic operational amplifier current-to-voltage converter will show underdamped second-order response to step inputs. This is not discussed in standard texts. It is shown that the transfer function of the amplifier must be treated as a complex variable in order to understand the response and to apply correct compensation. The response of commercial operational amplifiers is shown to fall into two categories: those which may be easily compensated and those which cannot be satisfactorily compensated.

Low noise and drift by parallel amplifiers

A low noise and low drift amplifier has been constructed using several monolithic operational amplifiers in parallel. It is shown that each amplifier may be connected by only three resistors. An input noise of 0.15 μV (p–p) in the band 0.1–10 Hz was obtained with six amplifiers, and the noise is expected to decrease as N−1/2 as the number of units is increased.

High slew rate monolithic operational amplifier using compatible complementary P-N-P's

An internally compensated monolithic operational amplifier, fabricated using only junction-isolated bipolar processing, slews in excess of 500 V//spl mu/s, and settles to within 0.1 percent in 200 ns as a pulse inverter. Performance in the noninverting mode is only slightly degraded in comparison with the inverting mode. In addition, the following performance levels have been achieved: 50-MHz unity-gain bandwidth with 96-dB open-loop gain, 30-mW quiescent power at /spl plusmn/3 V, /spl plusmn/50-mA output current capability, and output voltage to within 0.5 V of either supply. In order to achieve the above performance, the following innovations were made: 1) a process for junction-isolated compatible complementary p-n-p transistors with low collector series resistance, 2) a high-speed class-B output stage, 3) push-pull middle stages, 4) driven internal reference voltages locked to the noninverting input, and 5) very small voltage drops across large internal shaping capacitors which permit use of high-capacitance junctions.

A fast-settling monolithic operational amplifier using doublet compression techniques

A new high-speed monolithic operational amplifier is described which uses an improved feedforward circuit configuration to achieve a total acquisition time (slewing plus settling) of 650 ns with a 10-V input step without compromising dc performance or requiring costly nonstandard processing.

Nanowatt operation of monolithic operational amplifiers : R. A. Rikoski and J. L. Aldrich. Int. J. Electron.36, 329 (1974)

Nanowatt operation of monolithic operational amplifiers : R. A. Rikoski and J. L. Aldrich. Int. J. Electron.36, 329 (1974)

Recent advances in monolithic operational amplifier design

The state of the art in monolithic operational amplifier design is surveyed. A set of large- and small-signal performance parameters are defined and discussed. Relationships between the important operational amplifier parameters of slew rate, offset voltage, and unity gain bandwidth are demonstrated. The dependence of settling time upon the fine structure of the open-loop frequency response is discussed, and the recent technological and circuit design approaches to the minimization of settling time are reviewed.

Nanowatt operation of monolithic operational amplifiers†

A study was made of two micropowered operational amplifiers to determine degradation of unity gain frequency response, open-loop gain, and slow rate in amplifier circuits and maximum frequency of oscillation in Colpitts and Wein bridge oscillators as programmed. Quiescent current was reduced below specified operating levels into the nanoampere region.

An externally controllable monolithic operational amplifier : T. Furuhashi, H. Ayoama, I. Sasaki and S. Nakazawa. International Solid-State Circuits Conference, Philadelphia, Digest of Tech. Papers (1972), p. 176

An externally controllable monolithic operational amplifier : T. Furuhashi, H. Ayoama, I. Sasaki and S. Nakazawa. International Solid-State Circuits Conference, Philadelphia, Digest of Tech. Papers (1972), p. 176