Showing papers on "FET amplifier published in 1973"

Noise compensation techniques for bioelectric potential sensing

Abstract: A measuring circuit having one or more inputs connected to one or more bioelectric sensing electrodes couples its output to a waveform display or recording device in a manner to remain ungrounded and additionally has its common point maintained at the common voltage of a body under measurement. Undesirable common voltage variations in the body other than the desired bioelectric signal are sensed and the amplifier common point is varied in voltage in a similar way. A second amplifier connected in a unity gain voltage follower mode has an output that drives the amplifier common point. This second amplifier is connected to two electrodes, one of which is connected to an input of the second amplifier and the other of which is connected to a common reference point of the second amplifier.

Complementary field-effect transistor amplifier

Abstract: A complementary field-effect transistor (FET) amplifier is biased to a given operating point by applying a reference potential to its input terminal and varying the operating potentials supplied to the amplifier in accordance with its output signal. At least one other complementary FET amplifier, integrated upon a common substrate with the first amplifier, receives operating potentials which also vary in accordance with the output signal of the first amplifier for maintaining the quiescent operating point of the other amplifier at a value substantially equal to the given operating point of the first amplifier.

Asymmetrical dual-gate FET

Abstract: A dual gate FET is described wherein the second channel is made more conductive than the first such that when employed as an amplifier or a mixer circuit, zero bias is required from the gates to ground.

Feed-forward amplifier system

Abstract: A feed-forward amplifier system for producing a high output with low distortion and noise across a wide frequency band. An amplified signal is compared with a time-delayed unamplified signal in a sampling loop to isolate the noise and distortion components produced by the main amplifier. These noise and distortion components are then amplified by an auxiliary amplifier and combined with the amplified main signal to effectively cancel the error thereof. The output impedance of the main amplifier is completely mismatched with respect to the other components of the system and signals incident upon the output, although reflected off the main signal amplifier, do not reappear at the output because of the cancellation characteristic of the correction loop.

Circuit for shifting and amplifying input voltages

Abstract: A circuit for shifting and amplifying input voltages includes a p-channel enhancement-type FET and an n-channel deep-depletion type FET which are adapted to be alternatingly rendered conductive and nonconductive. A first source of reference potential is connected to the n-channel deep-depletion type FET and a second source of reference potential is connected to the pchannel enhancement-type FET, which sources of reference potential are adapted to be coupled to an output terminal when their respective FETs are rendered conductive. A breakdown voltage device and a second n-channel deep-depletion type FET are provided, according to one embodiment of the invention, and are arranged such that the second FET acts as a current source to break down the breakdown device. The breakdown device thereby properly translates the input voltage, applied at the input of the circuit, to appropriate levels to control the p-channel enhancement-type FET and the first n-channel deep-depletion type FET. According to another embodiment of the invention, another pchannel enhancement-type FET is provided in order to pull up the input voltage.

Variable-gain amplifier

Abstract: A variable-gain amplifier comprises a transistor with an emitter connected in a degenerative emitter-follower circuit which includes a PIN diode traversed by a current injector in the form of an operational amplifier, the PIN diode forming part of a negative-feedback path extending from the output to the inverting input of the operational amplifier. To achieve a gain characteristic whose logarithm varies linearly with a control voltage, this control voltage is fed to the same inverting input through an amplifier circuit with an exponential characteristic, including another operational amplifier provided with an input transistor. A temperature-compensating circuit, preceding that input transistor, comprises still another operational amplifier having a further transistor inserted in its negative-feedback path. The variable-gain amplifier may be included in one of two conjugate (sum and difference) channels of a monopulse radar.

Self-biased complementary transistor amplifier

Abstract: A complementary symmetry field-effect transistor amplifier employs a feedback path between the input and output terminals thereof. A second pair of complementary symmetry field-effect transistors in series with the transistors of the amplifier is employed to control the operating potentials applied to the amplifier. In one form of the circuit, the signal employed for controlling the conductance of the second pair of transistors is the output signal of the amplifier.

Automatic gain control system and amplifier of controllable gain

Abstract: An automatic gain control system incorporating a novel amplifier of controllable gain is described. The amplifier is d.c. coupled throughout and capable of wideband operation. It employs a cascoded differential transistor amplifier for producing the principal voltage gain supplemented by input and output emitter followers. Gain control is achieved by the application of gain control potentials to the bases of the upper rank transistors. Gain reduction is produced first in the upper rank by the controlled degeneration produced by a pair of nonlinear impedances in series with the emitter leads of the upper rank transistors, and sequentially in the lower rank transistors by the controlled degeneration produced by two pairs of nonlinear impedances coupled in a degenerative feedback path about the lower rank transistors and in the input circuit to a pair of input emitter followers. In addition, the amplifier produces an indication of gain control action which, when the amplifier is used as an intermediate frequency amplifier of a television system, permits one to derive a second gain control signal, which after thresholding may be used for further gain reduction in the tuner. The amplifier is adapted for integrated circuit fabrication.

High speed magnetic deflection amplifier having low-power dissipation

Abstract: A high speed magnetic deflection amplifier using switched voltages and a high impedance voltage amplifier for providing a high voltage drive with a minimum of power dissipation and with a relatively wide bandwidth. The voltage amplifier stage is designed to handle slew voltages while normally operating at character writing levels with relatively low power by floating the voltage amplifier on the output stage in a bootstrapped manner. A high impedance push-pull current drive is utilized to provide the voltage gain stage so that very little standby power is required. High power is consumed only during the relatively small time in which the amplifier is slewing.

High speed transistor difference amplifier

Abstract: A high speed, high input impedance difference amplifier in which a symmetric two branched circuit has opposed matched input transistors. An input signal into the matched input transistors appears again at the output electrodes for subsequent amplification. A pair of transistors cross coupling the circuit branches performs part of this amplification, while keeping inter-electrode capacitance in each branch to a minimum since the cross coupling transistors may be operated at a high current level without affecting input impedance.

High voltage amplifier

Abstract: A high speed, high voltage DC coupled linear amplifier includes a series string of transistor amplifying stages, means for biasing the junctions of each of the transistors substantially equal, means for enhancing the response speed of the amplifier and means for protecting the transistors. In another embodiment, an upper and a lower string of the aforementioned type of amplifiers are connected by means of a diode to operate the two strings in a push-pull fashion in response to an input signal.

Driver with two FET's connected in series - has feed-back capacitor whose charge and discharge are controlled by third FET

Abstract: The junction point between the first two FETs is the circuit output; the first FET gate is connected to an input terminal, and the gate of the second is connected through a feed-back capacitor to the above junction point. The third FET is controlled by a control voltage derived from a pulse voltage applied to the input, and dynamically increased during the charge phase; the third FET gate is capacitively coupled to the input; or it is so connected to a voltage divider circuit, that a biasing voltage is applied to the coupling capacitor before the beginning of the feed-back capacitor charge.

Method and arrangement for limiting the output signal amplitude of a video amplifier during fly-back highlight discharge

Abstract: A method and apparatus for amplifying television picture signals. The amplified television picture signals from an amplifier are monitored by a circuit arrangement including a Zener diode. When the amplitude level of the amplified signals exceeds a predetermined value, the Zener diode becomes conductive and an auxiliary signal is generated. A normally high resistance semi-conductor arrangement is connected in parallel with the high resistance in the input circuit of the amplifier. The semi-conductor arrangement is normally non-conductive, and in such cases, the effective load impedance at the input of the amplifier is substantially equal to the high resistance. When the auxiliary signals are applied to the semi-conductor arrangement, the latter becomes conductive to thereby provide a substantially lower resistance in the input circuit of the amplifier. In the latter case, the voltage levels developed at the input of the amplifier are limited, to thereby limit the amplitude of the amplified signals at the output of the amplifier.

Electronic hybrid amplifier

Abstract: An improved bidirectional amplifier using the inversion of signals across the output of a transformer having a balanced load is disclosed. The signals for the desired direction are inverted relative to one another by the transformer and fed to the inputs of a difference amplifier. The signals are algebraically summed by the amplifier to comprise an output approximately double that of either input. Reflected signals for the unwanted direction are not balanced and thus are not inverted across the transformer. When these signals are fed to the difference amplifier they are cancelled within the amplifier since there is no difference between the signals.

Noise pulse rejection circuit

Abstract: A circuit for rejecting pulses having a width less than a predetermined amount uses a single amplifier. The pulses are fed to the amplifier through a resistance-capacitance charging circuit. The resistance element is shunted by a pair of switched low impedance circuits which are controlled by the output signal of the amplifier to selectively permit current flow through only one of the circuits.

Fail-safe selectable low-pass filtering

Abstract: This invention relates to a vital type of selectable active lowpass filtering circuit. The selectable low-pass filtering circuit includes a half section resistance-capacitance filter network and a variable gain transistor amplifier. The input of the transistor amplifier is coupled to the half section resistance-capacitance filter network and the output of the transistor amplifier is selectively coupled to one of a plurality of load resistors each of which establishes a different gain for the transistor amplifier.

Half-bridge audio amplifier

Abstract: A half bridge transistor audio amplifier circuit has a Class B complementary symmetry transistor amplifier and a Class B transfer amplifier whose idling current variations are cancelled.

Pulsed ultrasonic flaw detector

Abstract: The present invention relates to a Pulsed ultrasonic flaw detector designed to determine the location, size and character of internal defects in materials. An operational amplifier of the flaw detector includes a current generator circuit coupled to a capacitor that forms a control signal. The current generator has a controlled internal resistance and employs AC positive feedback provided by one of the amplifier stages of an operational amplifier. The output stage of the operational amplifier is coupled to the amplifier of the reflected signal receiver via an AC negative feedback circuit employed in one or several stages of this amplifier.

Transformerless full wave rectifier and direct coupled product modulator

Abstract: A circuit which in one configuration may be used as a rectifier and in another configuration as a direct coupled product modulator comprising a pair of transistors coupled to the input, a first integrated circuit amplifier controlling the transistors and a second integrated circuit amplifier obtaining its input inverting input from one transistor and its non-inverting input from the other and providing the final output is shown. In the rectifier configuration the signal to be rectified is applied to both the two transistors and the first amplifier with the amplifier output selectively grounding a respective one of the transistors on respective positive and negative cycles causing the second amplifier to output a uni-polar signal. In the modulator configuration the carrier is applied to the first amplifier and will modulate the signal input to the transistors through similar grounding action. Both configurations are able to handle small signals and provide variable gain a feature not present in prior art devices using transformers.

Biasing circuit for differential amplifier

Abstract: A circuit for establishing the quiescent bias current of a differential amplifier with active collector loads (transistor loads). The collector current of an auxiliary transistor, held at the same base-emitter potential as the active loads, is applied to the input circuit of a current amplifier which supplies from its output circuit the combined emitter currents of the differential amplifier transistors. The base currents of the auxiliary transistor and of the active load transistors are decoupled from the input circuit of the current amplifier so that variations in such currents do not affect the quiescent biasing of the differential amplifier.

Power amplifier with self biasing and insensitivity to temperature variations

Abstract: A power amplifier having means for self biasing an emitter follower output stage over a range of temperatures comprises two matched transistors having the bases thereof directly coupled together such that the base-emitter potentials of the transistors are equal in magnitude and opposite in direction. Consequently, the output current is dependent only upon the value of the input current and resistance and the output resistance. A particular embodiment for this power amplifier utilizes two symmetrical power amplifier circuits that are complementary to one another in a push-pull arrangement.

Variable q if amplifier

Abstract: An Intermediate Frequency amplifier in a television receiver uses a dual gate field-effect transistor with an unbypassed source resistor. The dual gates are connected to a source of composite television signal and to a source of an automatic gain control signal. For weak signal conditions, the automatic gain control signal produces negative voltage feedback across the unbypassed source resistor, varying the output impedance of the field-effect transistor which is in parallel with a tuned circuit. The change in output impedance changes the Q of the tuned circuit and changes the response curve of the Intermediate Frequency amplifier.

Cascade direct-coupled amplifier

Abstract: A cascade direct-coupled amplifier comprising a current-absorbing circuit whose absorption current increases or decreases in proportion to an increase or decrease in the supply voltage of the amplifier, thereby to make the dynamic range of the amplifier wide.

IMPATT-Diode Power Amplifiers for Digital Communication Systems

Abstract: lMPATT-diode amplifiers with a power output of 1.0 W have been developed for use in an 11-GHz digital radio. Two types of amplifiers, a multistage reflection amplifier and a hybrid amplifier containing an injection-locked oscillator stage, have been evaluated by measuring the bit error rate degradation due to the amplifier. System test data show that the stable amplifier introduces little or no errors while the injection-locked oscillator (ILO) often introduces an error-rate floor.

Filament quality monitor - with photoelectric pickup , fet and operational amplifier as comparator

Abstract: An electronic filament quality monitor has a photoelectric measuring pickup which controls via an amplifier a cutter knife. The measuring pickup is connected in parallel to a field-effect transistor which keeps, independent of any quasi-stationary changes by voltage fluctuations, the electric parameters of the pickup constant. The field effect transistor controls an operational amplifier with a desired value setter on its inverting input acts as a comparator.

Charge circuit for field effect transistor logic gate

Abstract: A logic gate having a field effect transistor (FET) connected between an output capacitor and an input logic network. An electrical contact provided to the FET base (substrate) region receives a precharge signal for precharging the output capacitor through the FET base-drain diode junction and for precharging capacitance of the logic network through the FET base-source diode junction. The logic network is evaluated following the precharge interval to conditionally discharge the output capacitor through the FET as a function of the logic state of the network. The invention herein described was made in the course of or under a contract or subcontract thereunder, with the Air Force.

Method and apparatus for tuning an amplifier circuit

Abstract: A method of adjusting a tuned circuit receiving power from an amplifier and transferring power to a load includes the steps of adjusting the amplifier power output to a low value and temporarily introducing an impedance between the amplifier and the tuned circuit, the temporary impedance approximating the proper load for the amplifier when operating at its normal power levels, adjusting the tuned circuit for maximum power output at the lower power level, removing the impedance and thereafter operating the amplifier at its normal power level. An apparatus for performing the method includes a resistance device which is temporarily switched in parallel with the output of the amplifier, the resistance approximating the proper load impedance for the amplifier when operating at its normal power level, and means for reducing the power level of the amplifier, by lowering the screen voltage, for example, and adjusting the tuned circuit for maximum power output as indicated by an output power detector. The output power detector may include an audio frequency device which produces an audible output signal, the frequency of which is a function of the output power level.