Showing papers on "Operational amplifier published in 1974"

A simple three-terminal IC bandgap reference

Abstract: A new configuration for realization of a stabilized bandgap voltage is described. The new two-transistor circuit uses collector current sensing to eliminate errors due to base current. Because the stabilized voltage appears at a high impedance point, the application to circuits with higher output voltage is simplified. Incorporation of the new two-transistor cell in a three-terminal 2.5-V monolithic reference is described. The complete circuit is outlined in functional detail together with analytical methods used in the design. The analytical results include sensitivity coefficients, gain and frequency response parameters, and biasing for optimum temperature performance. The performance of the monolithic circuit, which includes temperature coefficients of 5 ppm//spl deg/C over the military temperature range, is reported.

The monolithic op amp: a tutorial study

Abstract: A study is made of the integrated circuit operational amplifier (IC op amp) to explain details of its behavior in a simplified and understandable manner. Included are analyses of thermal feedback effects on gain, basic relationships for bandwidth and slew rate, and a discussion of pole-splitting frequency compensation. Sources of second-order bandlimiting in the amplifier are also identified and some approaches to speed and bandwidth improvement are developed. Brief sections are included on new JFET-bipolar circuitry and die area reduction techniques using transconductance reduction.

A versatile active RC building block with inherent compensation for the finite bandwidth of the amplifier

Abstract: An earlier paper by the authors describes an easily trimmed universal building block for active RC filters which possesses the valuable characteristic that, with suitable design, the Q -value can be made approximately independent of the gain-bandwidth product of the operational amplifiers This makes the filter usable for high frequencies, while at the same time the dependence of the Q -value on temperature variations in the operational amplifiers is drastically reduced Design formulas are presented, as well as comparative measurements which verify the theory The building block is shown to have excellent characteristics both as a universal second-order building block and as a standard block for active ladder synthesis of bandpass filters

Circuit for dynamic control of phase shift

Abstract: A current controlled variable transconductance amplifier having a differential input stage and a current source output stage is employed with negative feedback, either through a buffer amplifier or directly, to provide various all-pass, low-pass or high-pass filter configurations, each with controlled bias current to the differential input stage for current control of the variable transconductance amplifier to provide dynamic control of phase shift and filter cutoff frequency.

Electronic personnel safety sensor

Abstract: An electronic personnel safety sensor is provided capable of causing a machine or operation to be shut off to prevent injury to personnel or damage to equipment protected, by detecting, indicating, and acting upon a predetermined increase or decrease in effective capacitance caused by the introduction, or intrusion, or withdrawal of material to or from a field or protection zone created by a suitably designed and connected electrode structure. The sensor is operable in a fail-safe manner inasmuch as it does not contain any single component, part or electrical connection, the failure or removal of which would cause the sensor to permit the protected machine or operation to operate. The sensor embodies circuitry wherein all activated units thereof are connected in series and are furnished an enabling signal from a common source. The initial signal may be provided from a crystal controlled, amplitude regulated oscillator signal generator source and is AC coupled to a modified null electronic capacity sensing type bridge. The latter bridge has two symmetrically disposed arms, one of which contains a fixed reference capacitor and the other of which contains the combination of an antenna and an adjustable capacitance. The latter is used to bring the two arms of the bridge to the "null" set condition that corresponds with normal operation of the protected machine or implied non-penetration of the protection field. The original signal from the oscillator is modified by the bridge according to the state of balance. The portion of the signal passed on by the bridge is larger at a state of unbalance and a minimum but not zero, at optimum balance. This modulated signal is again AC coupled to the next stage, i.e., an operational amplifier via a suitable transformer but at the input of the operational amplifier the signal is processed to produce rectified AC with a polarized or DC component that in a specific manner in combination with the adjusted characteristics of the operational amplifier causes the latter and the following units including a normally open relay which has been moved to a closed contact position to deenergize, i.e., to completely and precipitously to effectively stop amplifying or passing the original signal if the unbalance of the bridge falls outside of prescribed limits.

Recent advances in monolithic operational amplifier design

Abstract: 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.

Differential charge amplifier for marine seismic applications

Abstract: A differential charge amplifier for use in towed marine seismic streamers and the like involving towed hydrophone arrays wherein the hydrophone outputs are conducted by long twisted pairs of leads to signal processing equipment, the differential charge amplifier including operational amplifiers connected to form charge amplifier stages having resistance-capacitance feedback circuits and a differential amplifier stage coupled to the charge amplifier outputs providing cancellation of common mode signals.

Electronic Circuits and Applications

Abstract: Partial table of contents: LEARNING THE LANGUAGE. Fundamental Concepts. Linear Resistive Networks. Dependent Sources. Operational Amplifiers. Capacitance and Inductance. ELECTRONIC DEVICES. Electrical Conduction Processes. Diode Circuits and Applications. Physical Electronics of Transistors. Large-Signal Transistor Circuits. Small-Signal Models and Circuits. LINEAR CIRCUITS AND SYSTEMS. Linear System Response. Frequency Response in Linear Systems. Signal-Processing in Linear Systems. APPLICATIONS.

Transfer function control networks

Abstract: A network particularly useful in thick or thin film circuitry for use in telecommunication systems provides either an all-pass or notch filter function with the same basic component layout but with variously dimensioned component values. The circuit consists of a differential input operational amplifier having both inverting and non-inverting inputs connected by way of first and second resistors respectively to an input terminal (the second resistor being in parallel with a first capacitor) and having its output terminal connected to its inverting input by way of a third resistor and connected by way of a fourth resistor in series with a second capacitor to its non-inverting input, the network having a reference terminal connected by way of a fifth resistor to the junction between the second capacitor and the fourth resistor so as to provide an input port between the reference terminal and the input terminal and an output port between the reference terminal and the amplifier output.

A fast-settling monolithic operational amplifier using doublet compression techniques

Abstract: 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.

A fast response conductivity amplifier for chemical kinetics

Abstract: A linear direct reading conductance amplifier which is capable of following conductance changes due to chemical reactions in solution is described. It utilizes the simplifications in circuit design offered by operational amplifiers and has a sensitivity of 0.05% in each of the six ranges covering 0.025-10-7 Omega -1. Reactions with half-lives from 2 ms to several hours may be followed.

Generation and classification of single amplifier filters

Abstract: A unified approach is presented for generating configurations for circuits containing one operational amplifier together with RC elements and capable of realizing a general second-order voltage transfer function. Systematic application of the generation procedure leads to various single amplifier biquads with the known circuits, as well as some new ones, obtained as special cases. The insight gained from the generalized approach as well as the results of a general sensitivity analysis (including the effects of the amplifier limited bandwidth) offer a method for categorizing and classifying single amplifier filters. The different filter classes are illustrated and compared with the aid of extensive design tables. General equations for the effect of the amplifier limited bandwidth are also given.

New active-gyrator circuit

Abstract: Ideal passive gyrators can be made using two operational amplifiers, and it has been proved that they cannot be made with only one amplifier. However, this latter proof led to the discovery that an ideal active gyrator can be made with only one amplifier. A circuit for doing this is presented here, and its behaviour when used in an inductance-simulating mode is analysed.

Low-sensitivity active filters using the operational amplifier pole

Abstract: The utilization of the operational amplifier pole in the design leads to filters with satisfactory high-frequency performance. The approach reduces the number of capacitors required leading to circuits suitable for integration. Circuit arrangements for a bandpass filter and a second-order Butterworth low-pass filter have been suggested using only resistors and two operational amplifiers. The circuits have low parameter sensitivities.

Relative humidity computer

Abstract: Apparatus for measuring relative humidity within a given environment includes first and second operational amplifiers connected in a positive feedback loop. The first amplifier supplies an input signal to the second amplifier enabling the second amplifier to provide an amplified output signal which is fed back to an input of the first amplifier. First and second thermistors, which sense dewpoint and ambient temperatures, respectively, within the environment, control the gain of the second amplifier in accordance with changes in relative humidity to permit the second amplifier to provide an output signal which varies linearly with percent relative humidity.

Variable gain electronic current transformer

Abstract: A variable gain electronic current transformer is disclosed which includes means for detecting the current flow into a power consuming system. An operational amplifier amplifies the detected current and the output of the operational amplifier is converted into a magnetic flux field which is directed onto one surface of a Hall effect element. A variable current source supplies current to a second orthogonal surface of the Hall effect element to thereby generate an output voltage which is directly proportional to the product of the output of the operational amplifier and the variable current source. This output voltage from the Hall effect element is coupled back to the input of the operational amplifier. A second Hall effect element is positioned in the flux field generated at the output of the operational amplifier and in addition has a second variable current source coupled to one surface thereof so that the output of the second Hall effect element is a voltage which is proportional to the product of the output of the operational amplifier and the second variable current source. Accordingly, the output voltage of the second Hall effect element is directly proportional to the product of the detected current and the output of the second current source and is inversely proportional to the output of the first variable current source to thereby provide a current transformer having a large dynamic range depending upon the variance of the outputs of the first and second variable current sources.

Ion-implanted JFET-bipolar monolithic analog circuits

Abstract: An ion-implant JFET-bipolar process developed for analog circuitry will be covered, citing applications for low-offset, wideband, fast-settling FET-input op-amp and a high-speed quad analog switch.

Design of RC-active networks using generalized-immittance converters

Abstract: A systematic RC-active network synthesis procedure for the realization of second-order transfer functions is proposed. The realization employs a single generalized impedance converter which can be implemented by using only two operational amplifiers. The sensitivity to passive element variations are found to be low. The sensitivity to variations in the amplifier d.c. gain is minimized and found comparable to that in other low sensitivity structures. A design procedure is developed in which tuning can be achieved by trimming only resistors. With the exception of one case, second-order sections can be cascaded without additional isolating amplifiers. The stability properties as well as the influence of the finite bandwidth of the amplifiers are examined. The design procedure is used to obtain a sixth-order Chebychev low-pass filter, and a sixth-order elliptic band-pass filter. Experimental results show that these realizations are insensitive to temperature and power supply variations.

Critical liquid-level warning circuit

Abstract: A critical liquid-level warning circuit for association with a liquid-level indicating circuit, the indicating circuit including a sensing device that provides a voltage which varies between upper and lower voltage limits as a function of the level of a liquid. The warning circuit is particularly suitable for use in indicating a low fuel level in the fuel tank of a vehicle and, in the preferred embodiment, includes a first operational amplifier responsive to the sensing device voltage and a second operational amplifier that controls the actuation of a warning device. A delay circuit is interposed between the first and second operational amplifiers. The output of the first operational amplifier changes from one condition to another condition upon occurrence of a critical liquid level. The delay circuit provides a voltage which varies in magnitude as a function of time elapsed subsequent to the change in condition of the output of the first operational amplifier. This variable voltage controls the second operational amplifier. Preferably, the second operational amplifier circuit includes means for delaying the de-actuation of the warning device, thereby, to prevent intermittent warning device operation.

Luminescent voltage indicator circuit

Abstract: A plurality of luminescent elements, such as light-emitting diodes, incandescent lamps or the like, are located adjacent each other, each connected to the output of a difference amplifier The respective inputs of the difference amplifier are connected, on the one hand, to a voltage divider to have different reference voltages applied thereto and, on the other, in common to the input voltage to be sampled so that, as the voltage changes between the amplification ranges of the difference amplifiers, the output therefrom will change in accordance with input voltage so that the brightness of the respectively connected luminescent elements will also change, thus providing gradual increase in brightness of any individual element as the voltage changes The difference amplifiers may be differentially connected operational amplifiers

Active hybrid circuit

Abstract: An active hybrid circuit for providing isolation between a signal receiving line and a signal transmitting line coupled to a two-wire telephone subset. The receiving line is coupled to a receiving amplifier having a differential output coupled to a pair of common terminals. The telephone subset is also connected to the two common terminals. The two common terminals are connected to the two inputs of a transmitting operational amplifier. The transmitting signal line is coupled to the output of the transmitting amplifier. A compensating network is connected between the input to the receiving amplifier and one of the inputs to the transmitting amplifier. The reflected signal produced at the output of the transmitting amplifier due to a received signal at the input to the receiving amplifier passing through the receiving amplifier and then through the transmitting amplifier is cancelled by an equal and opposite compensating signal occurring at the output of the transmitting amplifier by virtue of the received signal passing through the compensating network and the transmitting amplifier.

Anti-reset windup proportional and integral controller

Abstract: An anti-reset windup proportional plus integral controller connectable in a proportional control loop of a process control system includes a proportional amplifier circuit and an integrating amplifier circuit responsive to a command signal to provide proportional and integral signals, respectively, which are summed by a summing amplifier to provide a modified command signal having a proportional and an integral component. A signal comparator means compares the modified command with a pair of reference signals which define an output range for said summing amplifier and disables the integrating amplifier circuit, permitting the integrating amplifier circuit to unwind whenever the modified command signal is not within the output range.

Low voltage CMOS amplifier

Abstract: A low voltage CMOS amplifier, particularly adaptable for use with an oscillator in an electronic watch. The relatively large biasing resistor used in prior art CMOS amplifiers is eliminated and transistors are provided in a network to provide proper biasing and also enable the amplifier to operate at a lower power supply voltage than prior art amplifiers.

Comparison of a class of active filters with respect to the operational-amplifier gain-bandwidth product

Abstract: Abstracr-A class of positive-feedback active RC filters which realize high stable Q's is presented. This class generalizes the earlier circuits of Tarmy and Ghausi and of Moschytz. The performance of the circuits presented is analyzed using a one-pole rolloff model for the operational amplifier. The Q and wO variations due to one-pole rolloff are tabulated for different filters. It is shown that the positive-feedback filters have lower Q sensitivity to the gain-bandwidth product than the state-variable filter. The theoretical behavior of the circuit Q is experimentally verified.

Inductive displacement sensor apparatus

Abstract: A variable inductor having a U-shaped magnetic core with a short-circuiting plate providing a short-circuiting ring for both legs of the core movable along the core legs in response to a displacement to be measured is connected in an electronic circuit to generate oscillation of a frequency that is either directly or inversely proportional to the displacement. For the inversely proportional case, the variable inductance component can be combined with an integrator function and connected to an operational amplifier, for generation of the output frequency with a small number of electrical components. Additional circuit means may be used to improve linearity at higher output frequencies, or to provide arbitrary non-linear displacement-frequency characteristics.

Exact synthesis with real amplifiers

Abstract: Second-degree active filter circuits are synthesized with operational amplifiers having a single pole or two poles and one zero. The method is applied to obtain designs and sensitivities for six useful filter sections. It is shown 1) that the two-pole amplifier is sometimes not the better choice, even though it has more gain at the operating frequency, and 2) that sensitivities are optimized by tradeoffs involving positive feedback.

A high-Q temperature insensitive bandpass filter using the operational amplifier pole

Abstract: A bandpass filter using only two resistors and two operational amplifiers is suggested. The circuit has a Q equal to the ratio of the ressistors. While Q and gain are insensitive to temperature variations, the variations in center frequency is minimized uing a compensation scheme.

Protective circuit for transistor amplifier

Abstract: A protective circuit for a transistor amplifier is disclosed which includes a load impedance detecting circuit provided between an output terminal of a transistor amplifier and a load terminal, a circuit for detecting an abrupt surge voltage of a voltage source for the amplifier and a muting circuit are provided between an input terminal of the amplifier and a reference point, the muting circuit being operative to limit an input signal applied to the input terminal of the amplifier in response to output signals of the load impedance detecting circuit. A protective circuit having a thermal sensing circuit for detecting a temperature rise of an output transistor above a predetermined level which shuts off the amplifier is described as one embodiment.

Series-coupled emitter coupled logic (ECL) circuit having a plurality of independently controllable current paths in a lower plane

Abstract: Emitter-coupled logic (ECL) circuit employs differential amplifiers arranged in upper and lower planes and selectively controlled by respective groups of input signals. Each differential amplifier of the upper plane has the emitters of its transistors connected to the collector of a transistor in one branch of the differential amplifier of the lower plane. Additional parallel connected transistors provide an OR function of several input signals in the upper plane for each of the differential amplifiers of that plane and the input signals of the lower plane are applied to each differential amplifier of the upper plane, with the exception of the input signal associated with the branch of the lower plane differential amplifier associated with a particular upper plane differential amplifier.

Characteristics of nonideal operational amplifiers

Abstract: The departures of the operational amplifiers (OA's) from the ideal performance and their effect on VCV's in the inverting and noninverting mode are discussed. It is found that for the same ideal gain, the bandwidths for the inverting and noninverting modes are different, the former being less. Complete equivalent circuits describing the frequency dependance of the input and output impedances for both modes are given. In particular, the output impedance is shown to be inductive for the frequencies of interest, and this is also confirmed by experimental results.