Showing papers on "FET amplifier published in 1983"

Optical Control of GaAs MESFET's

Abstract: Theoretical and experimental work for the performance of GaAs MESFET's under illumination from light of photon energy greater than the bandgap of the semiconductor is described. A simple model to estimate the effects of light on the dc and RF properties of MESFET'S is presented. Photoconductive and photovoltaic effects in the active channel and substrate are considered to predict the change in the dc equivalent circuit parameters of the FET, and from these the new Y- and S-parameters under illumination are calculated. Comparisons with the measured S-parameter's without and under illumination show very close agreement. Optical techniques can he used to control the gain of an FET amplifier and the frequency of an FET oscillator. Experimental results are presented showing that the gain of amplifiers can be varied up to around 20 dB and that the frequency of oscillators can be varied (tuning) around 10 percent when the optical absorbed power in the active region of the FET is varied by a few microwatts. When the laser beam is amplitude-modulated to a frequency close to the free-running FET oscillation frequency, optical injection locking can occur. An analytical expression to estimate the locking range is presented. This shows a fair agreement with the experiments. Some suggestions to improve the optical locking range are presented.

Improving the Power-Added Efficiency of FET Amplifiers Operating with Varying-Envelope Signals

Abstract: A technique is proposed for improving the power-added efficiency of linear, class-A FET power amplifiers operating with varying-envelope signafs. It involves dynamically controlling the gate "dc" bias voltage with the envelope of the input RF signal. It is shown theoretically that this technique, which is referred to as "class A," results in a significant improvement in the power-added efficiency over standard class A, independently of the FET power gain. The efficiency is also better than that of standard class B if the FET gain is less than about 10 dB, which is the case normally encountered at higher microwave frequencies. The practical implementation of class /sup /spl equiv//A requires FET's with essentially linear drain-current-versus-gate-voltage transfer characteristics.

A voltage-controlled resistance with wide dynamic range and low distortion

Abstract: Field-effect transistors (FET) can be used as voltage-controlled resistors, provided operation in the saturation region is avoided. However, to keep distortion low, the magnitude of the drain-to-source voltage must be kept low. This is true even when drain-to-gate feedback is applied to linearize the drain-current versus drain-to-source voltage characteristics. It is shown here that by employing a dependent source and a FET, a voltage-controlled resistance can be realized which has a linear range considerably greater (an order of magnitude or more) than other FET voltage-controlled resistances. The resulting circuit is stable and easy to implement.

2-20-GHz GaAs Traveling-Wave Power Amplifier

Abstract: Power amplification in FET traveling-wave amplifiers is examined, and the mechanisms which limit power capability of the amplifier are identified. Design considerations for power amplification are discussed. A novel single-stage and two-stage monolithic GaAs traveling-wave power amplifier with over 250-mW power output in the 2-20-GHz frequency range is described.

NPN Operational amplifier

Abstract: An operational amplifier having an extremely high gain-bandwidth product The amplifier includes a gain cell with an active negative resistance circuit made up of two matched NPN transistors (18 and 20) with their bases cross-connected to their collectors, and with a differential pair of NPN transistors (14 and 16) having their emitters degenerated through the active negative resistance circuit The value of the negative resistance is chosen to negate other resistance values in the denominator of a fraction expressing overall amplifier gain, which is therefore maximized Since no PNP transistors are needed to maximize gain in the amplifier, NPN transistors can be used exclusively, and the amplifier can be more conveniently fabricated in integrated-circuit form, with a desirably wide bandwidth

Combined microwave parallel amplifier- RF attenuator/modulator

Abstract: A parallel channel microwave amplifier comprising a plurality of amplificon channels interconnecting a power-dividing matrix and a power-combining matrix. Each amplification channel includes a phase shifter, an attenuator and a power amplifier connected in series. The device functions as a combination of amplifier and an r.f. attenuator/modulator.

GaAs FET power amplifier module with high efficiency

Abstract: A high-efficiency GaAs FET power amplifier having a total efficiency of 70% and an output power of 2 W is realised in the 900 MHz band. A drain efficiency of 80% was achieved at a low operation voltage of 6 V. These high efficiencies were obtained by using the even-order harmonic tuning of an output matching circuit. Important parameters for achieving this efficiency are also clarified.

Overdrive thermal distortion compensation for a quinn cascomp amplifier

Abstract: The cascomp amplifier is modified to provide a dynamic biasing circuit which varies the bias point of the cascomp amplifier in proportion to the change in the true bias point of the main channel pair to allow full thermal V be error correction for overdrive conditions and for common-mode signals. A buffer amplifier senses the average voltage of the main channel input transistor emitters and generates a voltage proportional to this average which is added to the biasing network for the cascomp amplifier common-base amplifier transistors.

A 60 GHz GaAs FET Amplifier

Abstract: Using a 1/4 µm gate structure, a new millimeter wave FET device has been developed. This device, in a waveguide/MIC amplifier circuit, has demonstrated gains of 5.0 +-0.5 dB from 55 to 62 GHz with a minimum noise figure of 7.1 dB at 60 GHz.

FET Amplifier with wide dynamic range

Abstract: A simple method for increasing the dynamic range of a GaAs FET amplifier. The drain resistance (RD) of the FET is adjusted to induce leakage current across the gate-source junction when excessive power levels are imposed on the gate. This current shunt (IS) is provided without added circuit components and therefore does not affect the sensitivity or bandwith performance of the amplifier.

Drive system for a semiconductor laser

Abstract: A transistor is connected between one terminal of a semiconductor laser and a power supply, a control terminal of the transistor is connected to an output terminal of an amplifier, a voltage is applied to one input terminal of the amplifier, and a junction of the semiconductor laser and a resistor is connected to the other input terminal of the amplifier.

Monolithic low noise common-gate amplifier

Abstract: A monolithic amplifier having a common-gate input stage with a device transconductance which is higher than required for input match, and a load impedance presented to the common-gate stage which is not conjugate matched. The present invention teaches a common-gate configuration using an FET with higher transconductance and a higher output load impedance. Over narrower bandwidths, excellent input match is thus obtained with noise figures at least as good as those obtained with the common-source approach. This combination of noise figure and input match is achieved in a compact monolithic structure.

Wideband IF amplifier with complementary GaAs FET-bipolar transistor combination

Abstract: A wideband intermediate frequency (IF) amplifier including a GaAs FET input portion and a bipolar transistor output portion is disclosed. The high gain of the GaAs FET over higher frequencies is complemented by the high gain of the bipolar transistors at lower frequencies to provide high amplifier gain over a large bandwidth. The GaAs FET and bipolar portions are coupled by means of an equalizer circuit matching the two portions together only at the higher frequencies of the IF band to provide an inexpensive, high performance IF amplifier particularly adapted for use in a direct broadcast satellite receiver operating in the super high frequency (SHF) band.

Miniature acoustical transducer with filter/regulator power supply circuit

Abstract: A battery-powered miniature acoustical transducer system for a hearing aid, including a microphone and an amplifier, has a combination filter and voltage regulator incorporated in its power supply circuit; the filter/regulator includes a field-effect transistor having its drain and source electrodes interposed in series between one battery terminal and a first power terminal of the amplifier, a resistor connecting the source and gate electrodes of the FET, a transistor having its emitter and collector interposed in series between the other power terminal of the amplifier and the gate electrode of the FET, and a junction diode connected from the FET source electrode to the transistor base, the diode junction and the base-emitter junction of the transistor both having highly non-linear voltage/current characteristics.

12-GHz-Band Low-Noise GaAs Monolithic Amplifiers

Abstract: One- and two-stage 12-GHz-band low-noise GaAs monolithic amplifiers have been developed for use in direct broadcasting satellite (DBS) receivers. The one-stage amplifier provides a less than 2.5-dB noise figure with more than 9.5-dB associated gain in the 11.7-12.7-GHz band. In the same frequency band, the two-stage amplifier has a less tlhan 2.8-dB noise figure with more than 16-dB associated gain. A 0.5-µm gate closely spaced electrode FET with an ion-implanted active layer is employed in the amplifier in order to achieve a low-noise figure without reducing reproducibility. The chip size is 1 mm x 0.9 mm for the one-stage amplifier, and 1.5 mm x 0.9 mm for the two-stage amplifier.

Stabilized high efficiency radio frequency amplifier

Abstract: A high efficiency radio frequency amplifier (50) which includes stabilization circuitry (100) which is selectively actuated during periods of time when undesired amplifier circuit operating conditions are present which tend to cause amplifier oscillation. Otherwise, the stabilization circuit (100) remains in effect decoupled from the amplifier so as not to unnecessarily draw power from the amplifier circuit (50) when its action is not required to prevent undesired oscillation of the amplifier.

Semiconductor integrated circuit device with output stage

Abstract: A semiconductor integrated circuit device comprises an output-stage MIS FET (3,4,12,17) and an internal circuit MIS FET (3, 4, 12, 16). The output-stage MIS FET has a channel length 2 greater than that L 1 of the internal circuit MIS FET and also has a gate insulator (17) thickness greater than that (16) of the internal circuit MIS FET.

MOSFET sense amplifier circuit

Abstract: A MOSFET sense amplifier applies both input signals to both input transistors of a common-gate sense amplifier; each input signal being applied to the source of one input transistor and the gate of the other, thereby effectively doubling the applied input signal.

Preamplifier for a wide range neutron flux monitoring system

Abstract: A preamplifier for a wide range neutron flux monitoring system is disclosed. The preamplifier contains first to fifth amplifiers and a selection switch. The first amplifier for high frequency band amplification has a low input impedance circuit. The second amplifier for low frequency band amplification has a high input impedance circuit. Either of the first and second amplifiers can provide a path for the neutron flux level signal derived from a detector according to the frequency of the neutron flux level signal. The third amplifier (pulse amplifier) amplifies the output signal of the first amplifier and transfers the amplified signal to a pulse signal counting system. The lower frequency band Campbell signal is applied to the Campbelling system, through the second amplifier, the fourth amplifier (low frequency band Campbelling amplifier), and the selection switch. The higher frequency band Campbell signal is applied to the Campbelling system, through the first amplifier, the fifth amplifier (high frequency band Campbell amplifier), and the selection switch.

Fluctuation-free input buffer

Abstract: An input buffer for a semiconductor circuit is provided with a source follower circuit composed of a first FET whose gate electrode has an input connected thereto, and a second FET of the same conductivity type as that of the first FET, whose drain electrode is connected to a source electrode of the first FET directly or through at least one level-shifting diode and whose gate electrode is supplied with a control voltage. The input buffer also includes a FET inverter circuit connected to the drain electrode of the second FET directly or through at least one level-shifting diode. An output signal for the input buffer is derived from the FET inverter circuit. A particular advantage of the present invention is that it permits the input buffer to switch its output from one level to another in response to input signals falling within a predetermined voltage range regardless of logic threshold level fluctuations in the FETs and fluctuations in supply voltages coupled to the input buffer.

Novel design of travelling-wave FET

Abstract: In the letter we propose a novel travelling-wave FET, in which an additional image gate is placed beside the drain of the FET as a phase velocity synchroniser. Small-signal analysis is given in the light of coupled wave theory and shows that the device is capable of high gain and wide bandwidth amplification. The easy adjustment of phase synchronisation and compability of the conventional FET fabrication technique make it promising for high-frequency distributed amplification.

Bootstrapped shunt feedback amplifier

Abstract: An improved bootstrapped shunt feedback amplifier is provided in which a minimum number of transistors are arranged to provide a higher slew rate of output voltage at lower power, while minimizing distortion and thus providing a more precise signal replication. Features include the use of three-terminal composite transistors to increase bandwidth and bootstrapping to improve amplifier response while reducing voltage stress on the active devices.

MOS Power amplifier circuit

Abstract: A MOS power amplifier circuit comprised of a load driver including two p-channel MOSFETs connected in series, a preamplifier for amplifying an analog input signal and supplying the amplified one to the gate of one of the MOSFETs and for rendering the impedance of the two MOSFETs low; and an inverting amplifier for invert-amplifying the output signal from the preamplifier and supplying the amplified one to the gate of the other MOSFET. The operating voltage of the preamplifier and the inverting amplifier is higher than that of the load driver.

Push-pull amplifier

Abstract: For a satisfactory cross-over behavior of the transistors T1 and T2 of push-pull amplifier comprising an input 2 and an output 3, it is necessary that the sum of the base-emitter voltages of the transistors T1 and T2 remains substantially constant. For this purpose a first voltage-current converter 5 is coupled between the base and the emitter of transistor T1, the inverting input of this converter being coupled to the base of transistor T1 via a first reference-voltage source 8 and the non-inverting input to the emitter of transistor T1. Similarly, a second voltage-current converter 9 and a second reference-voltage source 12 are arranged between the base and the emitter of transistor T2. The output currents of the first and the second voltage-current converters 5 and 9 are compared with each other in the combining circuit 14 which drives the control amplifier 15, which in its turn controls the base-emitter voltage of transistor T2 in such a way that the sum of the base-emitter voltages of transistor T1 and T2 remains constant. The push-pull amplifier exhibits a minimal amount of second-harmonic distortion, because only the difference of the errors introduced by the first and the second voltage-current converters 5 and 9 is of importance in this respect and these errors are substantially equal to each other due to the method of fabrication of the voltage-current converters.

Telephone handset amplifier circuit

Abstract: A rocker switch is operated by the handset user to vary the impedance of a FET. The FET impedance varies in proportion to the duration of operation of the switch. The handset receiver "volume" increases or decreases in proportion to the FET impedance. An electret condensor microphone stabilizes the receiver supply voltage and provides improved transmitter linearity and low distortion.

Low-Noise, Low Power Dissipation GaAs Monolithic Broad-Band Amplifiers

Abstract: Low-noise, low dc power dissipation GaAs monolithic amplifiers have been developed for use in VHF-UHF mobile radio systems. The developed amplifiers have two-stage constuction, where gate width for the first stage is 1000 µm, and for the second stage is 500 pm. Using this circuit configuration, both noise figure and bandwidth have been improved. To maintain the uniformity for the ion-implanted active layers and to reduce gate-source resistance R/sub S/ and gate-drain resistance R/sub D/, the "closely spaced electrode FET" was adopted. The FET enables low drain voltage operation, resulting in low dc power dissipation. The developed amplifier for the FET threshold voltage VT= --0.6 V provides a 3-dB noise figure, less than 170-mW dc power dissipation, 9-MHz-3.9-GHz bandwidth with 16-dB gain. It can operate under a unipolar power source. When external choke inductors were introduced for the amplifier, 120-mW dc power dissipation has been achieved. It has also been demonstrated that the amplifier for V/sub T/= --0.6V, which is inferior to the amplifier for VT= -2.7V regarding gain-bandwidth product and power efficiency under the same dc power dissipation, however, has an acceptable performance for use in the mobile radio systems.

Receiver including FET frequency mixer

Abstract: A receiver including an FET frequency mixer is disclosed. A local oscillator generates a local oscillator signal which is applied to a first amplifier whose gain is varied as a function of a control signal applied thereto. The output of the first amplifier is applied to a first gate electrode of the FET frequency mixer. A high-frequency signal received by the receiver is applied to a second amplifier whose gain is also controlled by the control signal. The output of the second amplifier is applied to a second gate electrode of the FET frequency mixer. The control signal is generated as a function of the output of the FET mixer.

Telecommunication operational amplifier

Abstract: A single stage high performance operational transconductance amplifier consists of a pair of p-channel load field effect transistors, a pair of n-channel type cascode field effect transistors, a pair of n-channel differential field effect transistors and an n-channel current source field effect transistor. This amplifier has improved performance in terms of noise and power supply rejection as compared to conventional CMOS amplifiers.

A 6-GHz 80-W GaAs FET Amplifier with TM-Mode Cavity Power Combiner

Abstract: A novel 8-way divider/combiner using TM010- and TM020-mode cavities was developed, with an insertion loss of 0.2 dB and a bandwidth of 600 MHz at 6 GHz. An 80-W broadband GaAs FET amplifier with combining efficiency of 85 percent was successfully demonstrated using this power divider/combiner.

Photodiode amplifier with a wide dynamic range

Abstract: Fibre-optical links contain relay stations inserted at particular distances, in which the light signals are converted into electrical signals and are again amplified. Since the light power emitted by the fibre-optical link is comparatively very low and, in addition, can fluctuate within a certain range, a corresponding amplifier is proposed, the gain of which can be varied in dependence on an externally applied control voltage. The amplifier is built up of two amplifier stages, a drain-source path of a field-effect transistor being connected in parallel with the collector resistor of the first amplifier stage so that the effective collector impedance and thus the gain can be varied in dependence on the voltage applied to the gate terminal of the field-effect transistor. The invention is used, in particular, in the input amplifiers of fibre-optical links.