Showing papers on "FET amplifier published in 1978"

CMOS Memory sense amplifier

Abstract: A complementary metal oxide semiconductor (CMOS) field effect transistor (FET) memory sense amplifier to detect a relatively small differential voltage that is superimposed on a relatively large common mode precharge signal. The sense amplifier is implemented so as to provide latched output signals after a short time delay and in response to sensed input signals that are supplied via a pair of data bus lines.

Protected amplifier apparatus

Abstract: This disclosure relates to an amplifier incorporating various devices for detecting parameters such as average power, peak power and signal voltage to be used to provide the feedback signals for automatic level control of an RF amplifier whose output signal is passed through an antenna coupler to an antenna. These detection devices allow normal operational level setting as well as minimizing the chance of overloads resulting in amplifier circuit failure during tuning conditions.

Quaternary FET read only memory

Abstract: A quaternary FET read only memory is disclosed wherein each FET storage element in the array has its threshold adjusted by ion-implantation to one of four values. Each FET element in the array has its drain connected to a drain potential VDD. A binary input signal from a conventional binary, true/complement generator will then enable the gate of a selected FET storage cell and the output potential at the source of that selected storage cell will be VDD minus the customized threshold voltage of that storage cell, which is output at an output node. The signal on the output node is a quaternary signal which may be amplified by a quaternary sense amplifier circuit and then converted from quaternary to binary signal by means of a converter. The quaternary read only memory is capable of storing twice as much information per unit area as is a conventional FET binary read only memory. The concept may be expanded to N levels of information storage, using FET array devices with N different threshold voltages.

Operational amplifier hybrid system

Abstract: This hybrid circuit utilizes two amplifiers such as operational amplifiers without transformers. A bridge arrangement is used in which there are four impedances, the line being one impedance. One amplifier is the second amplifier which is connected across two points of the bridge as a differential amplifier. The other amplifier is the first amplifier which is connected across the other two points of the bridge. One wire of the line acts as a common point for the bridge and the amplifier system. The bridge is a balanced configuration.

Current-voltage characteristics, small-signal parameters, and switching times of GaAs FET's

Abstract: A new two-dimensional model of a GaAs FET is proposed. The model takes into account diffusion processes and Gunn-domain formation under the gate but it requires a very small computer time. The electric-field profiles under the gate, current-voltage characteristics, the dependences of the transconductance and gate-to-source capacitance on the drain voltage, and the dependences of a characteristic switching time and power-delay product on the device thickness are calculated. The results of the calculation agree well with the experimental data found earlier by other authors. The proposed model can be used for a computer-aided design of GaAs FET amplifiers and logic elements and also for a comparative study of GaAs and InP MESFET's.

Servo amplifier for an electrically damped accelerometer

Abstract: A servo amplifier system for an accelerometer includes a torque coil. A torque coil is included in the output circuit of a first amplifier. A position sensor circuit develops a signal corresponding to the position of the coil which is applied to the input circuit of the first amplifier. An element, which may be a resistor, senses the current through to the coil and produces a voltage which is applied to a second amplifier having a low impedance output circuit. The output signal from the second amplifier is fed back to the input circuit of the first amplifier. Means are associated with the second amplifier to comply with the scaling and bandwidth requirements of the system.

Rom memory cell with 2n fet channel widths

Abstract: An FET read-only memory cell capable of storing more than one bit per cell. The channel geometry of the FET cell is selected to provide an electrical output that is characteristic of a predetermined combination of bits. For example, the FET channel width can be selected to provide one of 2 n predetermined output voltage values which correspond to the 2 n possible arrangements of n bits. The read function utilizes 2 n -1 sense amplifiers, which are connected to the FET. Each sense amplifier is selectively activated at a separate one of 2 n -1 voltage levels which is intermediate two adjacent values of the 2 n output voltages. The collective outputs of the sense amplifiers drive a logic circuit for decoding the values of the n data bits represented by the FET channel width.

Motor overload protection circuit

Abstract: Motor overload current is sensed and coupled to the input of an operational amplifier, causing the amplifier output to invert and charge a plurality of parallel connected capacitors. When the overload condition is present for a predetermined time, the capacitors are sufficiently charged to change the output state of a second operational amplifier. A diode is coupled between the output and the input of the second amplifier and is poled to latch the second amplifier into its inverted state when the capacitors have reached the predetermined charge. A luminous source, such as a light emitting diode, is coupled to the output of the second amplifier and becomes non-luminous in the inverted state of the second amplifier. The diode is photo-coupled to a photo conductive circuit for disabling the power coupling to the motor circuit when the diode is non-luminous.

Signal amplifier system for controlled carrier signal measuring sensor/transducer of the variable impedance type

Abstract: A controlled carrier current measuring sensor/transducer signal amplifier system comprising a carrier oscillator for providing a carrier voltage oscillatory signal of known frequency and fixed voltage magnitude. A differential amplifier has the carrier voltage oscillatory signal supplied to one of its inputs. A reference impedance and a variable impedance sensor transducer are connected in a series circuit across the output of the differential amplifier and a first feedback signal is fed back to a second input of the differential amplifier with the first feedback signal comprising the sum of the voltage across the reference impedance and the variable impedance sensor transducer. A buffer amplifier has its input connected to the juncture of the reference impedance and the variable impedance sensor/transducer for deriving an output voltage representative of the instantaneous value of the voltage across the variable impedance sensor/transducer. The output voltage signal from the output of the buffer amplifier is fed back to a third input to the differential amplifier in opposition to the first feedback signal for regulating the current supplied through the reference impedance and the variable impedance sensor/transducer to a substantially constant value whereby the output voltage signal from the output of the buffer amplifier provides a measure of the impedance of the variable impedance sensor/transduer. Preferably, the system further includes shielded conductors interconnected between the reference impedance and the variable impedance sensor/transducer and between the juncture thereof and the input to the buffer amplifier and the output from the buffer amplifier is fed back to the shielding of the shielded conductors whereby the effects of stray capacitance on any measurement obtained from the variable impedance sensor/transducer are minimized.

Apparatus for protecting power transistors in an h configuration power amplifier

Abstract: This invention relates to the protection of power transistors in an H configuration power amplifier which drives a D.C. motor. When the amplifier is switched off, it may be possible for the base terminals of the transistors to be turned "on" which results in the transistors conducting. If two series transistors conduct, the resulting short circuit may damage or destroy the transistors. This invention provides an easy and economical apparatus for protecting the transistors in the power amplifier by grounding the base input terminals of the power transistors during all times when the transistors are switched "off."

Asymmetrically precharged sense amplifier

Abstract: A sense amplifier having a transition point defining the signal level at its input above which it senses one binary condition and below which it senses the other binary condition includes precharge means for offsetting its input very slightly, above or below its transition point to place it in one of its two binary sensing states. The sense amplifier is suited for use with a memory array whose cells are coupled to the input of the sense amplifier via a single gating transistor which conducts in the (source or emitter) follower mode for the one binary condition and in the common (source or emitter) mode for the other binary condition. Following the precharge, the output of the memory cell is coupled to the input of the sense amplifier. For the cell storing the one binary condition for which the gating transistor conducts in the follower mode, the sense amplifier remains in the binary state to which its input was precharged. For the cell storing the other binary condition, the gating transistor conducts in the common mode and causes the sense amplifier to quickly change state.

Audio amplifier with low AM radiation

Abstract: An audio power amplifier is designed to have a wide band high fidelity response suitable for FM radio performance. The amplifier rolloff of gain versus frequency is made sufficiently steep to reduce the gain to a negligible level at the standard AM broadcast band. A stabilization network is incorporated into the amplifier to avoid instabilities that might result in oscillation. The amplifier has a very low AM broadcast band radiation so that it is useful in AM-FM radio receivers.

Wideband instrumentation amplifier with high common mode rejection

Abstract: A high performance, wideband instrumentation amplifier includes a main differential amplifier channel which receives an input signal having both differential and common-mode signal components, and a compensation amplifier channel which effectively removes the common mode signal component.

Remote control variable attenuation device for an antenna amplifier

Abstract: A variable attenuation device is provided for an antenna amplifier by providing high attenuation and low attenuation signal flowpaths connected to the amplifier input by respective pin diodes. The biasing of the diodes and, thus, the attenuation factor provided, is controlled in proportion to the output of a rectifying circuit which, in turn, provides a DC output proportional to the magnitude of a given polarity of the AC signal supplied to the amplifier from inside the subscriber's home.

Photo detector input circuit

Abstract: An improved input circuit is provided for an array of photo detectors. For each photo detector in the array, the circuit utilizes a first FET with a source for coupling to an output of a photo detector, a gate coupled to a first gate voltage, and a drain for coupling to an output circuit. The first gate voltage is provided by a feedback circuit which utilizes matched properties of adjacent FETs. In one embodiment, FETs are used in an open loop feedback circuit to reduce the input impedance seen by the photodiode at the source of the first FET. A similar objective is accomplished in another embodiment utilizing FETs in a closed loop feedback circuit. Further embodiments utilize FETs arranged as a differential amplifier with active loads to provide a low input impedance and a virtual ground at the source of the first FET.

Miniature guitar amplifier

Abstract: A miniature guitar amplifier, having at least one very small (13/4 inch) speaker driven by complementary transistors connected in an emitter-follower push-pull arrangement, is made to sound very much like a large guitar amplifier having one or more large (12 inch) speakers by providing negative feedback to an operational amplifier that drives the power transistors. The operational amplifier has a differential input stage to provide a noninverting input terminal for the signal from a guitar pickup and an inverting input terminal for the feedback signal.

Circuitry with unbalanced long-tailed-pair connections of FET's

Abstract: Unbalanced long-tailed-pair configurations of field effect transistors thermally coupled to each other and matched except for dissimilar threshold potentials are used as the input stage of a comparator or of a feedback amplifier for maintaining the difference between their gate potentials constant.

Reversible electrically variable active parameter trimming apparatus utilizing floating gate as control

Abstract: A continuously variable, reversible active circuit parameter trimming or adjustment method and apparatus are described. An active field effect transistor having a control gate to which a voltage is applied for the purpose of varying the conduction in the FET is achieved by supplying the control gate voltage from the stored voltage on a floating gate FET which has been charged to the desired variable level for controlling the conduction in the controlled FET at the desired operating point for parameter adjustment in an active circuit of which the FET may form a part. The floating gate FET structure can be electrically adjusted by charging or discharging the floating gate thereof which acts as a fixed memory to supply the appropriate control voltage to the controlled FET electrically connected thereto by a conductor connecting the control gate of the FET with the floating gate in the trimming or parameter adjustment floating gate FET element.

Microwave FET power oscillator

Abstract: First and second field effect transistors (FETs) each have a gallium arsenide substrate with an N-type active region that carries first and second electrodes in ohmic contact therewith and a gate electrode. The FETs are mounted in a flip-chip carrier that connects the first electrodes to ground. The FETs are biased to cause a current to flow from the first to second electrodes, whereby the first and second electrodes serve as drains and sources, respectively, of the FETs. The gate of the first FET is connected to a resonator. Additionally, a matching network connects the source of the first FET to the gate of the second FET. The matching network and the biasing of the first FET cause the gate input impedance thereof to be of a negative value that compensates for losses in the resonator. A load connected to the source of the second FET and the bias voltage cause the second FET to have a gate input impedance of a negative value that causes oscillation.

All FET Front-End for 12 GHz Satellite Broadcasting Reception

Abstract: A 12 GHz receiver front-end has been designed and realised which uses field-effect transistors for each of the three major functions of r.f. preamplifier, mixer and local oscillator. In each of these functions, the FET presents its particular advantages of low noise figure as an amplifier, a conversion gain as a mixer and a relatively high efficiency as an oscillator. An overall noise figure of 4 dB should be possible in production quantities. The structure and overall system performance will be described.

A small-signal analytical theory for GaAs field-effect transistors at large drain voltages

Abstract: Small-signal microwave performance of GaAs field-effect transistors (FET's) at large drain voltages is investigated, using a new analytical model which takes into account the carrier drift-velocity reduction and saturation due to electron upper valley scattering, and the extension of the depletion layer towards a drain side. Both of these play important roles in FET operation at large drain voltages. Small-signal y-parameters are calculated and the transit time effect which occurs in high-frequency operations is shown explicitly. Equivalent FET circuit elements are derived from the obtained y-parameters. Their dependence on device physical parameters, as well as on dc bias conditions, is calculated. The theoretical results are compared with the measured small-signal characteristics of a practical power GaAs FET and a reasonable agreement between them is obtained.

Transistor amplifier circuits

Abstract: In a transistor amplifier circuit of the type wherein two pairs of circuits are used each including a source follower type field effect transistor in the input stage and a bipolar type transistor in the succeeding stage and wherein the paired bipolar transistors constitute a differential amplifier, a plurality of constant current sources are connected such that the sum of the currents flowing through respective transistors will be constant for the purpose of driving the field effect transistors with small voltage in an active region.

Bi-state linear amplifier

Abstract: A bi-state linear amplifier is provided which, in response to a first state of a control signal, functions as a linear amplifier, and in response to a second state of a control signal, is cut off to define a high output impedance. The amplifier includes a control circuit responsive to relatively low-current control signals for selectively opening and closing the internal amplification circuit of the amplifier.

Amplifier distortion reduction apparatus

Abstract: The use of a nonlinear device such as a diode inserted in series with the load impedance of a transistor amplifier stage will reduce even and odd order distortion and thus improve the overall linearity characteristics of the amplifier.

Radiation-hardened transistor amplifiers

Abstract: An amplifier transistor has its base-to-collector voltage maintained substantially zero, and its collector-base junction has in inverse-parallel connection therewith an auxiliary semiconductor junction exposed to the same transient ionizing radiation environment. Photo-currents generated in the collector-base junction of the amplifier transistor responsive to transient ionizing radiation are counteracted by the photo-currents concurrently generated in the auxiliary semiconductor junction, so amplification can continue without being unduly hampered by such radiation.

Microwave FET power circuit

Abstract: A field effect transistor (FET) is comprised of a plurality of unit transistors having a common gallium arsenide substrate with an N-type active region. Each unit transistor is comprised of a unit gate, a unit drain and a unit source. The FET is mounted in a flip-chip carrier that connects all of the unit sources together to form a first electrode of the FET. Additionally, the first electrode is connected to ground by the carrier. All of the unit drains are connected together on the substrate to form a second electrode of the FET. The FET is reverse biased to cause a current to flow from the first electrode to the second electrode, whereby the first and second electrodes are a drain and a source, respectively, of the FET.

FET Amplifier comprising a circulator for an input signal as an isolator

Abstract: In an FET amplifier comprising a series connection of a coaxial-to-waveguide converter and a circulator for supplying an FET with an input signal of a wide microwave band, such as an octave band between about 1 GHz and 12 GHz, a d.c. bias voltage is applied to the FET through the circulator from a terminator therefor. For this purpose, the terminator comprises an inner and an outer conductor insulated ohmically from each other and shunted for the microwave band, as by a capacitor of several picofarads. Preferably, a resistor and a third conductor are successively connected to the inner conductor with the capacitor placed at an end of the resistor remoter from the inner conductor and with a dummy for the input signal positioned between the outer and the third conductors.

Electronic switchover circuit

Abstract: There is disclosed an electronic switchover circuit which can eliminate noises caused when two or more input signals are electronically selected to deliver out one of these input signals. A plurality of differential amplifier sets each having first and second transistors of which the first transistor receives the input signal are provided for the circuit, and a control voltage is applied to the control terminal of a constant current source to enable only one of the plurality of differential amplifier sets to thereby deliver out the input signal applied to the one differential amplifier set while disabling the remaining differential amplifier set. The base of the first transistor of the respective differential amplifier sets is connected with a third transistor which operates in the opposite phase relationship to the associated differential amplifier set, whereby base potentials of the first transistors of the differential amplifier sets which are disabled can be kept constant.

A 30-GHz GaAs FET Amplifier

Abstract: A Ka-band GaAs FET amplifier with 11 dB maximum single-stage gain at 33 GHz has been developed. At reduced drain currents and drain source voltages, noise figures as low as 5.5 dB were measured, and minimum noise measures of 7.0 dB were obtained from the experimental data. The Hughes 0.5 mu m GaAs FETs used in this development were fabricated using electron-beam lithography. The device fabrication technology of these Hughes FETs and the design and performance of the 30 GHz FET amplifier are discussed in some detail.

Amplitude comparator with a differential amplifier

Abstract: An input signal is coupled via a capacitor to a base of a transistor which constitutes a differential amplifier with another transistor. The base of the transistors are respectively fed with first and second predetermined voltages via a pair of transistors so that the differential amplifier produces an output signal proportional to the difference between the peak value of the input signal and a predetermined value only when the peak to peak value of the input signal exceeds a predetermined voltage.