Showing papers on "Linear amplifier published in 1972"

Use of Four-Level Phase Modulation for Digital Mobile Radio

Abstract: The paper explains the advantages of and compares various forms of four-level phase modulation from the point of view of performance, implementation, and spectrum usage. The results are applicable to digital mobile radio systems employing a large number of transmissions in which cochannel and adjacent channel interference are experienced. Of particular interest is the extent to which the theoretical spectra may be realized with practical transmitters. Differences between theoretical spectra and those measured from practical power amplifiers are identified. A method of simulating the effects of power amplifier nonlinearities is described and results are presented which agree closely with measurements made on an actual power amplifier.

Electronic watt transducer

Abstract: A potential input circuit and a current input circuit, each having a transformer therein, receives the input information from the power line for which the true electrical power is to be measured. The scaled output from the potential input circuit, and a triangle wave signal from a generator therefor are coupled to a comparator (level crossing detector) employing an open loop operational amplifier (op amp) having an output controlling electronic switches to gate the current transformer secondary current, with a duty ratio proportional to voltage amplitude and polarity. The gated output of the current transformer is filtered and coupled through an amplifier, or directly, to an external load. The filtered output is in the form of a linear direct current analog of true power in the power line.

Low noise detector amplifier

Abstract: An amplifier of electromagnetic wave energy in the visible and infrared range includes a photo sensitive detector coupled to a pair of cascoded field-effect transistors arranged to operate at substantial unity gain. A positive feedback path includes the input capacitances of the amplifier reducing and thereby neutralizing the input capacitances of the amplifier. The bandwidth of the amplifier is extended relative to the neutralization of the input capacitances.

Method of and means for gain-ranging amplification

Abstract: A gain-ranging amplifier is disclosed comprising a plurality of fixed gain amplifier stages connected in cascade and means for taking the output signal from any one of the fixed gain amplifier stages. Control means are described whereby such output signal is taken from the amplifier stage immediately preceding the first such stage which is being overdriven at a particular point in time by the signal which is being amplified. Specific circuits are disclosed for use in seismic geophysical exploration applications and means for generating a signal representative of the amount of gain utilized in amplifying the input signal and for monitoring the input signal are described.

High power bridge audio amplifier

Abstract: A high power audio amplifier includes four power amplifier sections connected in a bridge, with the power supply connected to one opposite pair of nodes and the load terminals connected to a second opposite pair of nodes One of the load terminals may be connected to a ground reference potential and the power supply is floating with reference to ground First and second drive amplifiers are provided, with each of the drive amplifiers being connected to the two power amplifier sections connected to one load terminal The input signal to be amplified is applied to one input of the first drive amplifier and a feedback signal from the load terminal which is not connected to ground is connected to the second input thereof The second drive amplifier receives either the input signal or the signal from the load terminal, and compares the same with the supply potential to balance the bridge To protect the transistors of the power amplifier sections, the currents in the transistors of the amplifier sections driven by the second drive amplifier are sensed and used to control the first drive amplifier, to thereby protect the transistors in all of the power amplifier sections Auxiliary protection circuits are provided for the transistors in the power amplifier sections coupled to each drive amplifier

Electronic amplifier with dual automatic slope control

Abstract: An amplifier is characterized by electronically variable slopes (''''tilt'''') at the bounds of its signal amplification gainfrequency passband characteristic. Separate feedback circuitry is responsive to an associated one of two frequency-spaced pilot signals for suitably adjusting the response properties of the amplifier. The pilot signals may be specially generated, or may comprise components of the signal operated upon by the amplifier - such as one high band and one low band video carrier for a CATV television signal distribution application.

A 15-W monolithic power operational amplifier

Abstract: The design of a new general-purpose monolithic power amplifier functional block is described and the flexibility of the block in various applications is discussed. The effects of thermal coupling on the die between components in high-gain dc power amplifiers are examined and a technique is presented for the analytical evaluation of dc circuit performance in the presence of these thermal interactions. Experimental results from the 15-W amplifier are presented. A new integrated power transistor structure is described that includes emitter degeneration resistors as part of the emitter structure. Circuit performance is summarized.

Transducer amplifier with automatic balance

Abstract: An amplifier for strain gages and other transducers in quarter, half or full bridge configurations provides an analog output suited for measurement, control or display purposes. The amplifier includes temperature compensation and automatic zero balance, the former realized from the voltage-temperature characteristic of a silicon PN junction used to affect the offset of an integrated circuit amplifier stage. The signal for zero balance is derived from the amplifier output, sampled and retained in an analog to digital converter and reconverted to analog form for application to a stage of the amplifier in opposition to the measurement signal, resetting for zero balance being under manual control.

Null loop for correcting low frequency error signals in high performance amplifiers

Abstract: A feedback null loop includes a low drift, first loop amplifier connected to the output of a fast settling, large drift amplifier means which is to be corrected for AC and DC errors due to stray signal coupling. A second loop amplifier with high impedance is coupled to the low drift first loop amplifier via electronic switch means. A ground line is provided to the input of the large drift amplifier means; e.g., via the conventional multiplexer apparatus in a multi-channel data acquisition system, whereby the output voltage of the amplifier means is nulled to zero. Prior to opening the switch means in the null loop, a capacitor stores a fixed voltage representing the error signal. Thereafter, as the multiplexer apparatus selects successive channels of the data acquisition system, any DC off-set levels are balanced out via the temporarily stored capacitor voltage.

A 0.5-W CW IMPATT diode amplifier for high-capacity 11-GHz FM radio-relay equipment

Abstract: A stable CW reflection-type Si-IMPATT diode amplifier has been developed as a transmitting high-power amplifier for the 11-GHz-band FM radio-relay system. It is a solid-state 960-channel system with a nominal transmitting power of 500 mW. The circuit design of the amplifier with a unique stabilizing circuit which provides unconditionally stable operation, is described. Also described are the FM noise contributions due to the biasing circuit parameters and experimental results of the FM noise of a locked oscillator and a negative resistance amplifier. Applications of the amplifiers in other frequency bands are described along with data obtained from the amplifiers for use in communication systems.

1-2 GHz high-power linear transistor amplifier

Abstract: The development of an octave bandwidth, linear 1O-W amplifier using MIC techniques will be described. The amplifier consists of three hybrid-coupled balanced stages using ballasted transistors in special microstrip carriers.

Integrated differential amplifier

Abstract: An integrated difference amplifier comprising a gain controlled first differential amplifier arrangement which is suitable for amplifying signals of low value and a satisfactory signal-tonoise ratio. In case of an increasing signal intensity the first differential amplifier arrangement is cut off and the signal amplification is taken over by a second differential amplifier arrangement which is suitable for processing large signal amplitudes.

Amplifier with substantially zero distortion products

Abstract: An amplifier with substantially zero distortion products is disclosed. A circuit is provided that independently compares the signals in the amplifier output with all the signals provided by the amplifier input source and discriminates between the original signals (fundamentals) and non-original signals (distortion product, spurious signals, and noise, etc.) present in the output terminals of the amplifier or network. Having discriminated and isolated the nonoriginal signals these are then re-inserted back into the amplifier in such phase that provides cancellation of the internally generated products.

Current measuring circuit and method

Abstract: The current of a mass spectrometer collector is indicated by a circuit including an electrometer tube having a control grid connected to the collector. The electrometer tube is included in a d.c. amplifier having a negative feedback path including a very high valued resistor directly connected to the control electrode so that the collector current develops a sufficient voltage to be amplified to a detectable level by the amplifier. Automatic zero and reset control for the amplifier is provided by another d.c. negative feedback loop responsive to the amplifier output. The another negative feedback loop includes an operational amplifier integrator having an output connected to a screen grid of the electrometer tube. The operational amplifier integrator is selectively connected to the d.c. amplifier output so that when the mass spectrometer responds to a sample the integrator is not responsive to the d.c. amplifier output and the spectrometer current is indicated by a d.c. meter connected to the amplifier output via a variable gain operational amplifier.

Amplifier for use in communication systems

Abstract: An amplifier for use in communication systems in which the output lines supply power to the amplifier which can operate from either polarity of supply voltage which may also be a relatively low voltage. The amplifier receives an input signal and applies the signal to said pair of lines. In one embodiment of the amplifier it can operate at high gain in response to an input signal and low gain in absence of an input signal to provide suppression of background noise. Another embodiment provides control of the amplifier gain as a function of operating current to more closely match the output characteristics of carbon microphones. The amplifier disclosed is particularly suitable for integration into a silicon monolithic bipolar circuit.

A.c.-d.c. amplifier system

Abstract: A wide-band a.c., stable d.c., amplifier system employing a wide-band operational amplifier and an integrator-feedback high-gain essentially d.c.-amplifying operational amplifier. The system provides uniform gain over a wide band of frequencies, including low frequencies and d.c., with precise stability useful for instrumentation. Indication of abnormal operation is available.

Threshold independent linear amplifier

Abstract: Low level pulses in the order of 100 millivolts or less can be detected and amplified regardless of variations in the voltage required to turn on the active device used in the amplifier. This is achieved by coupling an active device between a capacitor and a capacitively loaded output line, charging the output line to a reference voltage, applying a level setting voltage to the device to turn on the device; charging the capacitor to a voltage substantially equivalent to the level setting voltage to turn off the device while maintaining it such that any input signal superimposed on the level setting voltage will cause the device to again turn on and discharge the capacitively loaded output line thereby amplifying and inverting the superimposed input signal. The invention is particularly useful for sensing random access integrated semiconductor memories. The invention may be employed in either bipolar or field effect transistor technologies.

Bio-isolated dc operational amplifier

Abstract: A bio-isolated DC operational amplifier is provided for use in making bio-electrical measurements of a patient while providing isolation of the patient from electrical shocks and the like, the circuit comprising a first operational amplifier coupled to the patient and having its output coupled in a forward loop through a first optic coupler to a second operational amplifier, the output of the second operational amplifier being coupled to suitable monitoring circuitry. The output of the second operational amplifier is coupled via a feedback circuit including a second optic coupler to the input of the first operational amplifier.

Channel switching phase interferometer radar receiver

Abstract: Errors causd by IF amplifier and phase detector imbalance and asymmetry are overcome in a phase interferometer radar receiver by ultimate application of the respective antenna inputs to different IF amplifier/limiter channels. The output of the IF amplifier channels are cross coupled and fed to a phase detector employing a quadrature hybrid. The output of the phase detector is switched in synchronism with the IF amplifier input and the non-linearities resulting from cross coupling are linearized.

Distortion reduction in a repeatered transmission system

Abstract: The distortion appearing at the output of a repeater having a non-linear power amplifier with local feedback as an input amplifier stage is substantially reduced by generating a compensating distortion component within an auxiliary network. The auxiliary network attenuates a signal derived from the input amplifier stage and amplifies the attenuated signal with an auxiliary amplifier having substantially the same gain and distortion characteristics as the power amplifier in the input stage. The output of the auxiliary amplifier is attenuated and combined with the output of the input stage to substantially reduce the distortion.

Electronic gain control

Abstract: An automatic gain control circuit is disclosed for varying the gain of an amplifier as a function of a separate control voltage. Feedback around the amplifier is varied independently from the amplifier output signal, changing the amplifier gain curve without changing the feedback control voltage therefor. Pulse-time modulation is used for feedback control with the pulse amplitude being proportional to the amplifier output and the pulse width a function of the control voltage. An electronic switch in the amplifier feedback path affords complete isolation between the driving voltage and the amplifier output signal. The switch is gated with a bistable multivibrator that is alternately triggered by pulses from a fixed pulse generator and pulses from a variable slope, ramp generator.

Thin-film injection-locked oscillators and negative-resistance amplifiers for 2-GHz radio repeater

Abstract: Injection locked oscillators (ILO) used as amplifying stages in a solid-state FM microwave radio repeater are presented. Circuit performances needed for such an application and design criteria used to obtain these performances are given. Two ILO modelling possibilities are analyzed and compared. Similarity between positive feedback model and negative conductance model is shown for circuits with a single resonator. Then the equivalence is extended to a more complex arrangement useful to increase the performances of the practical realization. The first model is still used to study the ILO overall performance and the second model to design the actual circuit. Tunnel-diode ILO with second-order passive network is described giving circuit design criteria and experimental results. Transistor negative conductance linear amplifiers are presented with a procedure for computer aided design of the passive network imbedding the active device. The result of the entire active network is a one-port circuit exhibiting a negative conductance constant with frequency in the whole tuning band. Transistor ILOs are obtained by means of a matching network between circulator and the negative conductance amplifier. Mention is made to the active stages implementation into thin-film microstrip configuration referring alumina thin-film technology.

Electronic switch for an operational amplifier circuit

Abstract: A technique for controllably supplying current from an operational amplifier to a load wherein the output circuit of the amplifier is connected to ground through a semiconductor switch. The current drawn by amplifier in response to its input signal when its output is connected to ground is then sensed and amplified for driving the load. When the amplifier output circuit is ungrounded by opening the semiconductor switch, the amplifier draws substantially no current and thus current to the load is shut off. An electronic circuit provides a delayed control of the semiconductor switch in the output of the operational amplifier.

A C-Band All Ferrite Integrated Wideband High Power GaAs Avalanche Diode Amplifier

Abstract: A C-band 4-stage, 20 dB gain, 3-watt 25% bandwidth all ferrite substrate integrated GaAs avalanche diode amplifier is developed. The design procedure, as well as the amplifier performance including amplifier phase characteristics, is described. A power combining circuit which increases the output power capability by a factor of two is included in the output stage.

Manual/automatic station for use in process control systems

Abstract: A manual/automatic station including two amplifiers and a switching circuit for interconnecting the amplifiers in either an automatic configuration or a manual configuration. In the automatic configuration, the two amplifiers are in series. In the manual configuration, the output of a circuit associated with the first amplifier receives a feedback current from the station load circuit. A shunt capacitor connected between an input to the first amplifier and the circuit output charges to the difference between a feedback voltage developed in the station load circuit and an automatic control signal. The output of the first amplifier, which becomes saturated in the manual configuration, is limited by Zener diodes. On return to the automatic configuration, the Zener-limited voltage across the shunt capacitor. The current establishes a ramp voltage across the input to the second amplifier and, consequently, across the load until the first amplifier is driven from saturation. The shunt capacitor passes changes in input signals to the second amplifier during ramping.

Variable compensation for feedback control systems

Abstract: The characteristics of a compensation network for an amplifier are varied in accordance with an electronic signal representing critical system parameters. A resistive reactive ''''T'''' branch is paralleled by a switching device and resistor. The parametric signal activates the switching device and the networks are connected between the input signal and an input of the amplifier.

Continuous amplifier assembly with drift correction

Abstract: An amplifier assembly for amplifying weak DC signals and having means for drift correction. The assembly includes commutating devices for causing it to operate cyclicly in two distinct operating modes, alternately of short and long duration. In the short sampling modes when the assembly input is zero, the drift of a first amplifier stage is sampled and stored in a memory and the assembly output is disconnected from the load. During the longer alternate modes when the DC input is applied to the first amplifier stage, the assembly output is connected to the load, the previously stored signal is supplied as a drift correction signal to one input of a differential input amplifier stage, and the other differential stage input is connected to the first stage output. The output of the differential amplifier stage yields the final output from the assembly; when such output is disconnected from the load during the short sampling modes, the value thereof is maintained across the load from a second memory charged from the assembly output during the previous longer mode.

Integral rf modamp

Abstract: An RF modulator amplifier in a first feedback loop includes a comparator which produces an error signal whenever the audio input differs from a sampled portion of an AM modulated output. The error signal controls the current supply to the last RF amplifier stage. The voltage at the last RF amplifier stage is maintained constant by a second feedback loop which includes a voltage detector which senses this voltage to generate a second error signal which is used to set the drive of first and second RF amplifiers.

Field effect transistor linear amplifier with clocked biasing means

Abstract: A self-biasing MOS linear amplifier is provided with improved means for maintaining the circuit biased to its linear amplification range. That means comprises a clocked feedback FET operatively connected between the output and input terminals and adapted to charge a storage capacitor at the input during a first clock interval, the bias level applied at the input being a function of the operating characteristic of the switching FET. The storage capacitor is effective to maintain the device so biased throughout the remainder of the clock cycle.