Showing papers on "Operational amplifier published in 1977"

Idealized operation of the class E tuned power amplifier

Abstract: The class E tuned power amplifier consists of a load network and a single transistor that is operated as a switch at the carrier frequency of the output signal. The most simple type of load network consists of a capacitor shunting the transistor and a series-tuned output circuit, which may have a residual reactance. Circuit operation is determined by the transistor when it is on, and by the transient response of the load network when the transistor is off. The basic equations governing amplifier operation are derived using Fourier series techniques and a high- Q assumption. These equations are then used to determine component values for optimum operation at an efficiency of 100 percent. Other combinations of component values and duty cycles which result in 100-percent efficiency are also determined. The harmonic structure of the collector voltage waveform is analyzed and related amplifier configurations are discussed. While this analysis is directed toward the design of high-efficiency power amplifiers, it also provides insight into the operation of modern solid-state VHF-UHF tuned power amplifiers.

MOS sampled data recursive filters using switched capacitor integrators

Abstract: A new technique to analog sampled data filtering is presented which can be fully integrated using MOS technology. Advantages of this new approach are reduced circuit complexity, low sensitivity to coefficient variations, and efficient utilization of silicon area. Performance of monolithic low Q(Q=1) and high Q(Q=73) filters are presented which were implemented using NMOS technology. In implementing the high Q filter a new operational amplifier design was used which had a 14-V output range, rms noise voltage of 45 /spl mu/V, an open-loop gain of 6000, and a unity-gain bandwidth of 2 MHz.

Operational Amplifiers and Linear Integrated Circuits

Abstract: 1. Introduction to Op-Amps. 2. First Experience with an Op-Amp. 3. Inverting and Noninverting Amps. 4. Comparators and Controls. 5. Selected Applications of Op-Amps. 6. Signal Generators. 7. Op-Amps with Diodes. 8. Differential, Instrumentation, and Bridge Amplifiers. 9. DC Performance: Bias, Offsets, and Drift. 10. AC Performance: Bandwidth, Slew Rate, Noise, and Frequency Compensation. 11. Active Filters. 12. Modulating and Frequency Changing with the Multiplier. 13. Integrated Circuit Timers. 14. D to A and A to D Converters. 15. Power Supplies. Answers. Index.

Harmonic output of class-E RF power amplifiers and load coupling network design

Abstract: Class-E RF power amplifiers have advantages of explicit a priori designability, reproducibility, high efficiency, and low-stress operation of the power output devices. The authors give information on harmonic output and explicit design criteria for harmonic-suppression networks to be used with class-E power amplifiers.

Potential of MOS Technologies for Analog Integrated Circuits

Abstract: Large-scale integrated circuits for many analog and combined analog-digital circuit functions are becoming feasible in N-channel and complementary metal-oxide-semiconductor technologies. Experimental results have been reported for analog to digital and digital to analog converters, a pulse-code-modulation voice encoder-decoder, and precision analog sampled-data frequency filters. Some of the key elements in these MOS circuits are precision-ratioed capacitor arrays, transistor analog switches, internally-compensated operational amplifiers, and offset-nulled comparators.

Amplifier protection circuit

Abstract: A protection circuit for a transmitter amplifier is provided in which separate VSWR (reflected power) control and separate temperature control is provided when the thresholds of either or both are exceeded. When the temperature of the RF amplifier is sensed and when this temperature exceeds a certain threshold level, the output level of the RF amplifier is adjusted to protect the amplifier. Separately, there is provided a means for sensing the ratio of the reflected power to the forward power and when this ratio exceeds a given threshold, the gain of the amplifier is cut back to thereby protect.

Complementary-symmetry amplifier

Abstract: A complementary-symmetry amplifier is described, wherein a CMOS inverter has its P-channel MOSFET paralleled by the emitter-to-collector path of a simultaneously conductive PNP bipolar transistor and has its N-channel MOSFET paralleled by the emitter-to-collector path of a simultaneously conductive NPN bipolar transistor. The amplifier switches very rapidly due to the high transconductances of the bipolar transistors, while the MOSFET's permit the output terminal of the amplifier to swing over the full range of available supply potential.

A practical introduction to electronic circuits

Abstract: Preface to third edition Preface to second edition Preface to first edition 1. Amplification and the transistor 2. The field-effect transistor 3. Thermionic valves and the cathode-ray tube 4. Negative feedback 5. Impedance matching 6. Semiconductor device characteristics 7. Amplification at high frequencies 8. Low-frequency signals, d.c. and the differential amplifier 9. Power supplies and power control 10. Pulse handling and time constants 11. Integrated circuit analogue building bricks 12. Positive feedback circuits and signal generators 13. Digital logic circuits 14. Microcomputer circuits and applications Appendix 1. Component identification Appendix 2. Transistor selection Appendix 3. Op amp data Appendix 4. Digital IC connections Appendix 5. Interfacing to the PC Bibliography Index.

Transconductance cancellation for operational amplifiers

Abstract: A low-cost internally compensated integrated-circuit operational amplifier occupying a small die area can be fabricated if the compensation capacitor value is low. This objective is attained when the amplifier-input-stage transconductance is reduced to a minimum provided the frequency response remains unchanged. A new technique, transconductance cancellation, meets the objective without extra devices or components.

Gyrotrons for high power millimeter wave generation

Abstract: The gyrotron is a new type of micrwave tube capable of producing high power output at millimeter wavelengths. Oscillator results have been described in recent Soviet publications This paper describes work in progress at Varian Associates, Inc. to develop an amplifier of the gyroklystron type to deliver 200 kW cw at 28 GHz. Considerable progress has been made with amplifier stability to the point that amplifier gains of up to 40 dB have been measured in a pulsed experimental amplifier. Current effort is concerned with improving efficiency. A pulsed oscillator is also described which produced 248 kW peak power at 28 GHz with 34% efficiency. A cw oscillator is under construction. Areas for future R and D are discussed. These include gyro-TWT amplifiers with increased instantaneous bandwidth (5 to 10%) and operation at harmonics of the cyclotron frequency to reduce the magnetic field requirements.

Current and voltage autozeroing integrator

Abstract: An autozeroing integrating circuit which compensates for input offset voltages and input current to the integrator differential amplifier During an integrate period, an input signal is integrated in the conventional manner, and a voltage is accumulated on the integrating capacitor The integrator may be reset to discharge the integrator capacitor in preparation for a new integration During reset mode, the integrator automatically corrects for input offset voltage errors in the amplifier by storing the offset voltage During an autozero mode, a charge is stored on a capacitor which provides via a buffer amplifier a current which compensates for the current flowing into the input of the integrator

C.M.R.R. analysis of the 3-op-amp instrumentation amplifier

Abstract: The c.m.r.r. performance of the 3-op-amp instrumentation amplifier is analysed and shown to be, in general, no better than that of a single-op-amp differential amplifier. Only under rather special conditions does the more elaborate amplifier have a c.m.r.r. advantage.

Four electrode conductivity sensor

Abstract: In a four electrode conductivity sensor, each pair of electrodes is coupled to a respective one of two operational amplifier circuits that establish a fixed potential relationship between the two potential electrodes so that current flow between the two current electrodes is maintained directly proportional to the conductivity of the solution. Specifically a direct or alternating excitation voltage is applied to the positive input of one operational amplifier, while the other receives a fixed reference potential input. The operational amplifiers supply a unity gain, noninverted output to the respective current carrying electrodes, while the potential electrodes are directly connected to the feedback input of the respective amplifier. The current flow between the current electrodes is measured as a voltage signal across a resistor with the operational amplifier output and remains directly proportional to the conductivity of the solution in which the electrodes are immersed, regardless of fouling of the electrodes by solution impurities and electrolysis effects. An alternating current excitation input can be applied through a coupling capacitor with each electrode also connected through a coupling capacitor to provide direct current that eliminates ground loop problems in the installation and use of metering and control equipment.

Acoustic feedback detector and automatic gain control

Abstract: A device for detecting the oscillating condition caused by the acoustic coupling between a loud speaker and a microphone at those frequencies which do not satisfy the Nyquist stability criteria, and for thereafter decreasing the system loop gain. The detection circuitry consists of a bank of phase lock loop detectors. Each phase lock loop within the bank covers a limited frequency range such that together the bank covers the entire audio band. Upon detecting an oscillation in the particular phase lock loop frequency passband, that phase lock loop control voltage is automatically internally adjusted to align the phase lock loop frequency with the oscillating frequency. An abnormal phase lock loop control voltage signifies the presence of an unwanted oscillating signal and is detected by circuitry which includes a diode peak detector followed by a pair of voltage comparators. Upon detecting the ringing condition, the loop gain is decreased until the ringing condition ceases. A digital up-down counter is employed to establish the loop gain. The output of this counter is applied to a digital-to-analog converter which in combination with an operational amplifier, a light emitting diode, and a photoresistor form an attenuator circuit which controls the loop gain. Provision is also made for automatically counting down the up-down counter by applying down clocks to this counter at predetermined intervals such that after a certain time period the loop gain is returned to a particular desired setting.

Controlled recovery automatic gain control amplifier

Abstract: An automatic gain control amplifier having a controlled recovery of gain is disclosed and includes a peak detector for generating an output when the amplifier output exceeds a predetermined level, a memory setting circuit responsive to the peak detector output, a memory controlled by the memory setting circuit, and a memory adjust circuit responsive to information derived from the amplifier output. The output of the memory controls an attenuator of the automatic gain control amplifier. Amplifier output level change detection circuitry is also disclosed and accepts the output of the amplifier for producing an output indicating amplifier output level changes exceeding a predetermined magnitude. The level change detection output controls the memory adjust circuit.

Data-in amplifier for an MISFET memory device having a clamped output except during the write operation

Abstract: In a MIS random access memory device including a data-in amplifier and MIS memory cells, a device is provided for holding the output level of the data-in amplifier at the precharge potential of the memory cells except during a write operation by controlling an input circuit and a driver circuit of the data-in amplifier through utilizing the read/write signal and the control signal for the memory. Data stored in the memory cells are free from the influence of the output of the data-in amplifier during a non-write operation.

Dopant profiles determined from enhancement‐mode MOSFET dc measurements

Abstract: Simplified algorithms are described which allow the determination of the dopant profile in the gate region of a four‐terminal enhancement‐mode metal‐oxide‐silicon field‐effect transistor (MOSFET). The method calls for the dc measurement of the source‐body voltage VSB as a function of the gate‐source voltage VGS for a fixed minority‐carrier channel current. The profile depth is proportional to dVSB/dVGS and the dopant density is inversely proportional to d2VSB/dV2GS. Only the oxide and silicon dielectric constants and the oxide thickness are needed in the computations. The data acquisition was computerized and includes the use of an operational amplifier circuit. The method is illustrated by the profile of a phosphorus layer implanted in an n‐type silicon substrate.

Self-compensating thermocouple reading circuit

Abstract: A plurality of thermocouples are connected to reading circuit conductors at an isothermal junction block, for selective connection to the input of an operational amplifier. The resulting output signals from the operational amplifier are monitored and stored in a computer. A reference thermocouple is selectively connected to the operational amplifier through a reference junction compensator -- the reference junction compensator provides a compensated connection of the reference thermocouple with the reading circuit conductors. The signal at the output of the operational amplifier when the reference thermocouple is connected at the input is also monitored by the computer and stored for processing. In the computer, the signal sensed and stored when the reference thermocouple is connected to the operational amplifier is subtracted from the sensed, stored signals generated when the other thermocouples are connected to the operational amplifier. This subtraction nullifies the offset error of the operational amplifier (and the offset error of other reading circuit electronics such as the multiplexer selectively connecting the thermocouples to the operational amplifier), and it corrects the temperature indications of the thermocouples by eliminating the error of the cold junction at the isothermal junction block. These corrections are inherent, and are maintained without any surveillance or periodic adjustment.

Automatic illumination compensation circuit

Abstract: A compensation circuit for use in a document reproduction system for correcting variations in white level occurring between different documents and due to nonuniformity of the scanning process including a variable voltage gain amplifier for compensatingly modifying the output of an image scanner and having a gain control system which drives the white level amplifier gain to a predetermined level so that the scanner output is made independent of certain well known causes of nonuniformity. The gain control system includes a comparator which compares the amplifier output to a white reference signal, a counter having a start count which may be present and which is incremented when the comparator output indicates that the amplifier output exceeds the reference signal, a memory which is addressed by signals developed by the scanner and which stores the output of the counter at intervals which in effect subdivide each scan line, the stored signals being used to preset the counter at the beginning of each particular scan interval, and a digital-to-analog converter for converting the counter output to a form which can be used to drive the amplifier.

Application, design and symbolic analysis of a current follower

Abstract: A new circuit called a current follower, is described. It may be used with voltage followers to replace operational amplifiers. The advantages are at high frequencies, where the operational amplifier is unsuitable because of its limited frequency response and slew rate. Basic applications for these purposes are given. An, analysis of the internal nonlinear equations of the designed linear circuit is given. The analysis of the linear model of this circuit shows a typical example of the application of the symbolic networkanalysis program Netform. Extremely short computation times are observed in a nontrivial situation, due to the newly implemented double sparse Laplace expansion (d.s.l.e.) method.

Voltage sensing circuit of differential input type

Abstract: A voltage sensing circuit of differential input type includes at least one differential amplifier circuit connected between two complementary data lines of a semiconductor memory. The differential amplifier circuit detects data in response to a minute potential difference between the data lines and amplifies the same by a substantial change in conductance gm of metal oxide semiconductor field effect transistors (MOSFET) used in the circuit. When data is read from a semiconductor memory onto the data lines, the differential amplifier sensing circuit detects the data quickly by detecting potential changes of the data lines.

Photo-current log-compression circuit

Abstract: A photoelectric current log-compression circuit includes a log-conversion diode, a photodiode and an operational amplifier for log-compression. In the negative feedback circuit of the operational amplifier is inserted a thermistor to control the amplification degree of the operational amplifier according to the current flowing through the log-conversion diode. Further, a forward voltage of a temperature compensating diode biased with a constant current is applied to the reference voltage of the operational amplifier.

Automatic frequency-tracking circuit

Abstract: A circuit for receiving an incoming RF signal incurring frequency drift and producing a local signal for tracking the incoming signal includes a phase-locked loop and means incorporated in the loop which compensate or correct for the frequency drift so as to maintain the loop locked on the incoming signal. The loop is defined by a phase detector, a DC amplifier and a voltage controlled oscillator connected in series. The correction means is coupled in parallel with the loop amplifier between the loop detector and amplifier at its one end and between the amplifier and a DC bias voltage supply terminal for the amplifier at its opposite end. The correction means is responsive to low frequency components of a DC voltage produced by the detector for changing, within preset limits, the DC bias voltage applied to the loop amplifier from the supply terminal as offsets in the DC voltage from the detector are caused by frequency drift of the incoming signal so as to maintain operation of the loop amplifier within its optimum bandwidth range.

Pressure to electric transducer

Abstract: A pressure to electric transducer is described employing an electrical capacitance formed by two parallel metal plates separated by a variable air gap, one of the plates being fixedly mounted and the other being movable to change the spacing in direct proportion to fluid pressure acting on an input element or capsule to which the movable plate is connected. The capacitance forms one leg of a negative feed back divider network, for controlling an operational amplifier so that its gain is directly proportional to the spacing of the plates. The amplifier is driven by a constant alternating current source so that its output is directly proportional to the applied pressure. The voltage output can be rectified and transformed in a conventional manner for transmission of a signal.

Temperature measuring apparatus

Abstract: An apparatus for measuring the temperature of a metallic body in a non-contact maner includes an electronic circuitry for measuring a change in the impedance of a detecting coil arranged oppposite to the metallic body The electronic circuitry comprises an operational amplifier, a negative feedback circuit with adjustable feedback factor, a positive feedback circuit, an oscillator, a phase shifter circuit and a synchronous detection circuit The change in the impedance of the detecting coil is caused by the effect of eddy current produced by the application of alternating field to the metallic body, and this impedance change is dependent on change in the temperature of the metallic body By adjusting the negative feedback factor βN of the negative feedback circuit and the phase angle θ of the phase shifter circuit in the electronic circuitry, the relationship between the distance measured between the detecting coil and the metallic body and the measured output level, the temperature measuring sensitivity relative to the temperature of the metallic body and the temperature measuring sensitivity relative to the measuring distance can be determined as desired

Operational amplifier with positive and negative feedback paths for supplying constant current to a bandgap voltage reference circuit

Abstract: A voltage regulator circuit including an operational amplifier having supply voltage terminals connected to a source of unregulated supply voltage and a two-terminal, essentially zero temperature coefficient, semiconductor bandgap voltage reference circuit connected in a negative feedback path between the output terminal and one input terminal of the amplifier. The amplifier provides a constant current source for the bandgap voltage reference circuit, and the amplifier and reference circuit cooperate to establish a regulated output voltage at the amplifier output terminal. A resistive divider network is connected in a positive feedback path between the output and a second input terminal of the amplifier to establish the value of the regulated voltage within a range of values between the bandgap voltage and the unregulated supply voltage.

Electronic kWh meter having virtual ground isolation

Abstract: An electronic kWh meter is disclosed which measures electrical energy consumed in an electrical system. A current transformer generates an analog voltage which is proportional to a current in the electrical system. An operational amplifier has an input resistor connected across the load impedance of the electrical system and has a feedback resistor connected across the input and output of the amplifier. The input resistance of the amplifier is very small compared to the resistance of the input resistor to thereby virtually isolate the operational amplifier from the electrical system. The operational amplifier generates an output signal which is proportional to the voltage across the load impedance in the electrical system. The inphase components of the voltage and current are multiplied to provide a signal which is proportional to the instantaneous power in the system. This signal is converted to a pulse train wherein each pulse represents a quantized amount of energy consumed within the system. The pulse train is accumulated, recorded, and a display is provided for indicating the energy being consumed within the system. Both single phase and polyphase embodiments of the meter are described.

Self-contained charge-coupled split-electrode filters using a novel sensing technique

Abstract: Self-contained single-chip charge-coupled split-electrode filters with 55 taps and a novel channel structure have been built with a double-level polysilicon NMOS process. Operating at a sample rate of 32 kHz, these devices provide a low-pass filter function with a passband from 0 to 3.2 kHz and a stopband above 4 kHz. The image charge on the sense electrodes is detected with a novel sensing circuit employing two on-chip operational amplifiers, one of which suppresses the common-mode signal on the two sense buses while the other one integrates the difference signal. In addition, the chips carry antialiasing prefilters, a correlated double sample-and-hold circuit to minimize reset noise and to restore the output signal, and all the necessary peripheral logic and biasing circuitry so that the devices can be operated from a single master clock and two power supplies of +12 and -5 V, respectively.

Adaptively biased differential operational amplifier for photo diode

Abstract: A differential amplifier has one input connected to a reference potential and a photo diode connected in series with a level shift to the other input. A negative feedback loop is also coupled into other input. This stabilizes the amplifier and, if the level shift is made equal to the reference potential, biases the photo diode to zero, thereby reducing leakage current. A second feedback loop is used to adaptively bias the tail current in the differential amplifier.

Complementary power saving comparator/inverter circuits

Abstract: A CMOS power saving comparator/inverter circuit includes a complementary differential amplifier, one input of which is coupled to a voltage input. Another input of the complementary differential amplifier is coupled to a voltage reference circuit which includes two relatively high value resistors coupled in series between a P-channel MOSFET coupled to the positive voltage conductor and N-channel MOSFET coupled to the ground voltage conductor. An output of the differential amplifier is connected to an input of a CMOS inverter having its output connected to an output of the comparator/inverter circuit. The transition point, defined as the value of input voltage at which the output voltage is equal to one-half of the supply voltage, is virtually independent of the P-channel and N-channel threshold voltages. The transition point is much sharper than the transition point for a conventional CMOS inverter, and much less dependent upon various manufacturing parameter variations. The DC current of the circuit drops to zero when the input is at V DD or at ground.