Showing papers on "FET amplifier published in 1979"

A New Method of Broad-Band Equalization Applied to Microwave Amplifiers

Abstract: A new approach to broad-band matching which bypasses analytic gain-bandwidth theory and directly utilizes measured real frequency impedance data is applied to gain equalization and low-noise design of GaAs Shottky-barrier FET amplifiers. Neither the equalizer topology nor the analytic form of the system transfer function are initially assumed. These result from the design process. Examples include an octave-band FET amplifier design and a low-noise FET amplifier design. The equalizers are realized with lumped elements or transmission-fine sections. A single basic least squares program implements the design procedure.

Dual-FET sample and hold circuit

Abstract: An improved sample and hold circuit is disclosed. One field effect transistor (FET) is used as a switch between a variable input voltage connected to the source and a holding capacitor connected to the drain on the output line. The sampling pulse is applied to the gate, and is unavoidably coupled through the gate-to-drain capacitance to become a noise pulse on the output line. To cancel this pulse, a second compensating FET is provided. The sources and drains of these FETs are connected and the gate of the second FET receives a sampling pulse of opposite polarity. The second FET is biased off but the gate pulse is coupled through the source and drain capacitance to the first FET where it is used to cancel the original noise pulse on the output line.

Circuit for measuring low capacitances

Abstract: A capacitance to be measured is connected between the input and output of an inverting amplifier. A bistable circuit has an input connected to the output of the inverting amplifier and an output impedance inversely proportional to the capacitance to be measured. A resistive feedback is connected from the output of the bistable circuit to the input of the inverting amplifier.

High bandwidth transversal filter

Abstract: A high bandwidth transversal filter is described having an input impedance matching network, a tapped delay line, a plurality of weighting amplifiers, a distributed summing circuit, and an output impedance matching network The delay line is implemented with a transmission line The input impedance of this transversal filter depends on the inductance and capacitance of the transmission line and the capacitance of the inputs of each of the FET's used as weighting amplifiers The gates of the FET's provide high impedance low loss taps of the delay line The weighting is accomplished by either varying the drain current of the FET's or by using capacitive voltage dividers to apportion the tapped signals The resulting weighted signals are applied to a distributed summing circuit which provides both high bandwidth summing and additional delays This summer is also implemented with a tapped transmission line The output impedance of this transversal filter depends on the inductance and capacitance of the summing line and the capacitance of the output of each FET The parameters of the transmission lines constituting the input delay line and the distributed summer can be selected to provide broadband impedance matching for the input and output of the filter The FET's thus act as high impedance taps, as weighting amplifiers, and as part of the input and output impedance matching networks

TTL to CMOS input buffer circuit

Abstract: A TTL to CMOS input buffer integrated circuit having an input terminal for connection to an output terminal of a TTL device is disclosed. The buffer circuit includes a first CMOS inverter connected to the input terminal, including a first p-channel FET connected to a supply terminal and a first n-channel FET connected to a ground terminal, wherein the drain of the first p-channel FET is connected to the drain of the first n-channel FET at a first node; a second n-channel FET having its gate connected to the input terminal and its source connected to the ground terminal; a third n-channel FET having its gate connected to the first node, its drain connected to the supply terminal, and its source connected to the drain of the second n-channel FET at a second node for forcing the potential at the second node to be less than the potential at the first node by the amount of the threshold voltage of the third n-channel FET; and a second p-channel FET having its gate connected to the second node, its source connected to the first node, its drain connected to the ground terminal, and its substrate connected to the supply terminal, for reducing the rate at which the third n-channel FET becomes conductive when gated on in a said integrated circuit in which the threshold of the n-channel FET's is greater than the threshold of the p-channel FET's.

GaAs Dual-gate FET frequency discriminator

Abstract: A microwave frequency discriminator comprising a dual-gate field effect transistor (FET) amplifier, bias circuits and a detector. The FET is biased to produce an output RF signal within a predetermined frequency bandwidth in response to an input RF signal. A limiter provides a substantially constant power level of the input RF signal to the FET. A detector biasing circuit is used to match electronically the output impedance of the FET to the input impedance of the detector. At such impedance conditions a dc output voltage of the detector varies substantially linearly throughout the frequency bandwidth as a function of the frequency of the input RF signal, approximating the characteristic of a frequency discriminator.

Power FET inverter drive circuit

Abstract: A half-bridge inverter having first and second power FETs is provided with a high-speed, highly efficient drive circuit for driving the FETs from a single control signal. A single 15 V supply provides energy for charging the gate electrode of the first FET, as well as for a floating source for charging the gate electrode of the second FET. A single bipolar transistor receives the control signal for controlling operation of the first FET, while a current source, a bipolar transistor in series with a resistor, receives the control signal to effect operation of a third bipolar transistor, thereby to control operation of the second FET.

Sliding power supply for RF power amplifier

Abstract: A sliding power supply for a radio frequency power amplifier provides power to the power amplifier that is indirectly controlled by the load impedance voltage standing wave ratio of the amplifier. The overall results being an enhancement or improvement in the efficiency of the RF power amplifier into a varying RF load mismatch.

Improvement of a Class-C Transistor Power Amplifier by Second-Harmonic Tuning

Abstract: Considerations for the effects of second-harmonic reactive terminations on the performances of a UHF class-C transistor power amplifier are presented. An experimental amplifier circuit design using coupled-TEM-bar transmission lines is described. This circuit can vary the fundamental and the second-harmonic impedance terminations of the amplifier independently. With this amplifier circuit, significant improvement in the performance characteristics of a class-C power amplifier were achieved by presenting proper values of second-harmonic reactive terminations, both at the input and the output of the transistor.

Floating shunt seismic amplifier

Abstract: A differential amplifier circuit comprised of two operational amplifiers for use as a differential output and differential input amplifier for any two-terminal impedance transfer function. The input impedance is very low between the two input terminals, yet it is very high between either input terminal and the common or ground terminal, thus giving this amplifier many of the desirable characteristics of a transformer-coupled amplifier. High common mode voltage rejection ratios can be achieved even when moderate differential imbalances exist in the input and feedback networks due to the unique balancing feature of the circuit.

Amplifier for driving electrostatic loudspeakers

Abstract: An amplifier for a capacitive load which includes a pair of high-voltage tube output circuits connected in a power output tube arrangement operating in push-pull for driving a capacitive load together with a feedback network connected between the Schmitt arrangement and a pair of transistors interconnected in a complementary difference amplifier circuit, the output of the complementary difference amplifier circuit connected to the driving tube of the power output tube arrangement to provide an amplifier output level having low distortion, positive DC centering and a high order of stability.

Common-emitter fT doubler amplifier employing a feed forward amplifier to reduce non-linearities and thermal distortion

Abstract: An improved common-emitter cascode f T doubler amplifier is provided with a feed-forward amplifier circuit to compensate for non-linearities and thermal distortion. The feed forward amplifier senses distortion at the emitters of the f T doubler amplifier transistors and injects a correction current into a pair of output nodes. The amplifier is also provided with a common-base transistor output stage.

Feed forward microwave amplifier for communication systems

Abstract: A microwave wide band feed forward amplifier consists of modular amplifying units and modular delay units adjusted to compensate said modular amplifying unit, two said amplifying units constitute the main amplifier, another two the error signal amplifier and a single module amplifier is connected between the input and the error signal amplifier. Wide band compensation of the 3rd harmonic level is obtained at high level.

PVF 2 Polymer Microprobe

Abstract: This paper describes the design and performance of a PVF2 microprobe for use in mapping the pressure field from arrays. For medical applications, the probe must have short pulse response (i.e., broad, flat bandwidth) in addition to high sensitivity, low noise, and a wide acceptance angle. The factors that influence critical parameters, such as ringing and delayed reverberations, are specifically discussed. The probe has a center frequency of about 3 MHz. It consists of a 1.5 mm diameter disc of PVFZ polymer (30 pm thick) operated well below its resonance to obtain very broad frequency response. The PVFz is completely encased in a metal cylinder to shield it from spurious electromagnetic interference and to protect the polymer from possible corrosion by external fluids. An FET amplifier is integral to the probe housing. The experimental performance of the probe is compared with theoretical predictions, acoustically and electrically. It is also compared with the performance of other probes, including a laser pellicle system, for pulse fidelity and signal-to-noise ratio.

Broad-Band GaAs FET Amplifier Design Using Negative-Image Device Models

Abstract: A new technique is presented for determining equivalent source and load device models applicable to GaAs FET or other devices for which measured data is available. The new technique provides a more accurate starting point for matching network synthesis, better prediction of achievable circuit performance, and does not require the unilateral device assumption. Simple computer optimization and elements with negative reactance slope parameters are utilized. A description of the method and examples of its application to GaAs FET amplifier design are presented.

Direct-coupled amplifier with output offset regulation

Abstract: In a direct-coupled amplifier circuit having a first-stage differential amplifier, the junction temperatures or voltages across junctions of differential transistors in the differential amplifier are controlled in accordance with the magnitude and polarity of an output offset voltage, thereby reducing the output offset voltage

Making a short-channel FET

Abstract: An improved Field Effect Transistor (FET) with a very small effective channel length is made by using, a first ion implantation to produce the source and drain regions of the FET and a second very shallow ion implantation next to the source region to produce the effective short channel of the FET. The effective channel of the FET is implanted to only a small fraction of the depth of the source and drain. The use of implantations instead of diffusions in the described manner in combination with the use of the shallow effective channel in the FET provides superior control over the threshold voltage of the FET and increases the operating speed of the FET.

A Microstrip Low-Noise X-Band Voltage-Controlled Oscillator

Abstract: Design and perfomance of an X-band microstrip bipolar varactor-tuned oscillator integrated with an FET amplifier is presented. Wide temperature operation (-55 to 71/spl deg/C), constant high power (0.5 W), low post-tuning drift (0.75 MHz) for 8-percent tuning range, and exceptionally low SSB phase noise (-125 dBc/Hz with GaAs hyperabrupt or -132 dBc/Hz with silicon abrupt tuning diode at 1-MHz modulation frequency) is reported. Extremely linear frequency-voltage characteristic is achieved with the GaAs hyperabrupt tuning diode for this oscillator without the need for complex Iinearizing circuitry. Circuit synthesis techniques and noise estimation criteria are presented which correlate with the experimental results.

Musical instrument performance amplifier

Abstract: The output section of a musical instrument performance amplifier comprises a pair of high impedance power field effect transistors connected to an output transformer to provide a relatively low push-pull drain load that effectively presents a high impedance constant current source to a loudspeaker. The amplifier, having such high impedance constant current source output, amplifies and sustains instrument sound, provides large amounts of power to the speaker over a wide range of speaker impedances, and enables production of high power harmonics.

Amplifier with input stage differential amplifying circuit

Abstract: To the respective drains of a pair of FET's which constitute an input stage differential amplifier circuit are cascade-connected a first transistor and a second transistor, respectively, whose bases are connected in common. To a pair of active elements of the next stage amplifier circuit is connected a detecting circuit for detecting the sum of the driving currents of these active elements. By the output of detection of the detecting circuit, the potential of the common base of the first and second transistors is controlled, so that the currents flowing through these first and second transistors are held constant, whereby the apparent load, for input signals, of the paired FET's is elevated.

FET driver circuit with short switching times

Abstract: A field effect transistor driver circuit responsive to a single input pusle generates a highly loadable output clock pulse with short rise and fall times, the rising edge being shifted relative to said input pulse by a controllable delay time but the trailing edge remaining practically undelayed. This advantageous pulse form is achieved through an improved controlling of a bootstrap output stage. Two preceding stages, i.e., a transmission gate and a delay stage supply two out-of-phase control pulses with high amplitudes and steep edges. Of essential importance is the novel delay stage which is designed as push-pull stage with a load FET and a driver FET. The gate of the load FET is controlled by the output pulse of the bootstrap stage 2 fed back via a third FET and by a capacitively coupled-in input pulse at the drain, whereas the gate of driver FET is controlled from the bootstrapped output of the transmission gate. The connecting point of load and driver FET represents the output of the delay stage. For the quick switching-on and delayed but speedy switching-off of the driver FET's of the bootstrap output stage a pulse equal in amplitude to the input pulse is generated. That pulse rising with equal speed and falling steeply after delay. The delay stage also controls advantageously the gate recharging of the isolation FET of transmission gate.

Integrated n.m.o.s. operational amplifier for c.c.d. transversal filters

Abstract: An integrated operational amplifier employing a new high-gain input stage and implemented with n.m.o.s. enhancement devices is reported. The circuit has been designed with reference to the output differential-charge amplifier of a c.c.d. transversal filter. The performance parameters of the amplifier are presented.

Crystal oscillator implemented with CMOS technology

Abstract: In a crystal oscillator for solid state wristwatches, the input of an impedance converter is connected to the output of a complementarily connected transistor amplifier which performs linear operation within its essential operating range, to thereby stabilize and decrease the output impedance of the amplifier on the average. The impedance converter includes one or more active elements such as MOSFET's, junction type FET's and bipolar transistors. A quartz resonator is connected between the input of the complementarily connected transistor amplifier and the output of the impedance converter.

Wideband high voltage video amplifier

Abstract: A wideband high voltage video amplifier shares the amplification of positive and negative signal peaks between positively and negatively charging output bipolar transistors, respectively, thereby circumventing distortion of the output signal by the base-to-collector junction capacitance of each transistor.

Telephone transmitter amplifier

Abstract: A telephone transmitter amplifier circuit is easy to manufacture in integrated circuit form and has a low power consumption. It has a microphone unit, and an operational amplifier including a differential amplifer. A grounded collector transistor is connected to the output of the differential amplifier and a constant-current circuit is connected to the emitter of that transistor. An output stage amplifier has a grounded emitter transistor having its base connected directly to the output terminal of the operational amplifier. A smoothing circuit smooths the voltage which is supplied from the telephone line to the amplifier. A voltage-divider circuit, at the output of the smoothing circuit, presets the operating points of the operational amplifier and the output stage amplifier. The output terminals of the output stage amplifier are connected in common to input terminals of the smoothing circuit.

High-fidelity speaker system

Abstract: A negative-feedback circuit for use with a moving-coil loudspeaker and a host amplifier modifies the feedback signal from the output of the host amplifier in such a say that the velocity of the voice coil of the speaker more closely follows the signal voltage input to the host amplifier. The power output of the power amplifier is delivered to the voice coil through a low resistance, and a high resistance feedback path is provided from each side of this low resistance to the input of the host amplifier. Other reactive, resistive and non-linear elements may also be used with the high resistance feedback paths for improved operation.

An X-Band GsAs FET Monolithic Power Amplifier

Abstract: Experimental results obtained with a monolithic, one-stage X-band power FET amplifier will be presented along with the CAD design techniques used. Some general considerations relating to the feasibility of GaAs as a monolithic circuit substrate will be given.

Direct-coupled amplifier circuit with DC output offset regulation

Abstract: A direct-coupled amplifier circuit includes an input stage differential amplifier comprised of a differential pair of field effect transistors and a pair of bipolar transistors connected in series with the differential field effect transistors, respectively and having their emitters coupled together. Gate electrodes of the differential field effect transistors are coupled to an input terminal and an output terminal of the amplifier circuit, respectively. The collector-to-emitter voltages of the bipolar transistors are controlled in accordance with the magnitude and polarity of an output DC offset voltage appearing on the output terminal so as to reduce the DC offset voltage.

Gas discharge lamp employing a pulse generator with a double stage amplification circuit

Abstract: A solid state ballast circuit for a discharge lamp includes a transistor oscillator with a current amplifier connected to a transformer one secondary winding of which is connected to the lamp and another secondary winding of which is coupled to the amplifier input An inductive choke coil is connected in the power circuit of the amplifier so that when the lamp burns out or is removed the operating frequency increase resulting from the decrease in load circuit capacitance results in an increase in impedance of the choke, drastically reducing current flow through the amplifier power circuit to prevent transistor damage or RF interference radiation The current amplifier disclosed is a two-stage emitter follower circuit