Showing papers on "Cascade amplifier published in 1976"

Weigh feeder system

Abstract: Disclosed herein is an automatically controlled weigh feeding apparatus including a container prefilled with a substance, a device for discharging the substance from the container at a controllable weight, apparatus for weighing the container and its contents and for producing an electrical signal proportional to that weight, a first amplifier for amplifying the electrical signal, a first analog-digital converter coupled to said first amplifier and a digital computer coupled to said first analog-digital converter for computing the weight of substance remaining in the container. A second amplifier is coupled to said first amplifier and a ramp off-set circuit which is controlled by the digital computer inputs a second signal to the second amplifier means having a controlled stepping output applied as a second input signal to the second amplifier to maintain the output of the second amplifier within a given selected range of amplitude during one time cycle of operation. A second analog-digital converter interposed between the second amplifier and the digital computer. The digital computer is adapted to compute a corrective signal based on the signal received for controlling the discharge of the substance from the container.

Amplifier for fiber optics application

Abstract: An amplifier for use with a photodiode in an electro-optical transmission ne. A transimpedance amplifier is connected to an output port of a photodiode and a T-network feedback circuit is provided as a feedback element in order to provide a significant increase in the transimpedance gain-bandwidth product.

Amplifier improvements for limiting clipping

Abstract: A differential amplifier is connected to an amplifier for comparing an amplifier input signal with the signal fed back by the amplifier feedback circuit. The output of the differential amplifier is coupled to a full wave rectifier the output of which controls an attenuator connected between a source of electrical input signals and the amplifier. When the amplifier is operating in its linear range, the differential amplifier inputs are identical and it does not produce an output. Under this condition, the input signal is not attenuated. However, in the presence of amplifier clipping, the differential amplifier produces an output which, after full wave rectification, operates to increase the attenuation, and thus reduce the amplitude of the signal applied to the amplifier; clipping is limited.

Amplifier with modulated power supply voltage

Abstract: The power supply voltage of an amplifier is modulated by a signal having a waveform that corresponds, at least in selective parts, to the waveform of the signal being amplified by the amplifier.

Instantaneous floating point amplifier

Abstract: An improved instantaneous floating point amplifier is provided having a plurality of cascaded amplifier stages, wherein the gain of a given stage of the amplifier is the square of the gain of the immediately succeeding stage of the amplifier. The number of amplifier stages which are required to implement the amplifier is minimized, and the control logic which is required to decide if a given stage is needed to amplify the input signal to a level within preselected limits is simplified. The amplifier has an automatic nulling feature which permits nulling of the amplifier without loss of data.

Method and a device for eliminating the residual error voltage of an amplifier

Abstract: The connections between the two inputs of an amplifier and the two outputs of a signal source as well as between the outputs of the amplifier and the inputs of a downstream output element into which the amplifier delivers a signal are inverted periodically and simultaneously and integration is carried out between the outputs of the amplifier and the inputs of the output element. In addition, the inputs of the amplifier are short-circuited periodically, the frequencies of inversion and of short-circuiting being multiples of each other.

Audio power amplifier

Abstract: An audio power amplifier can be operated in either class A, class B or class AB amplifier modes by selectively switching bias values set in a bias setting circuitry provided for a driver stage which drives the main power amplifier stage.

Limiting amplifier with adjustable limits

Abstract: A limiting amplifier includes an operational amplifier with three feedback loops. One loop controls the gain of the amplifier when the output signal is between the upper and lower limit. Each of the other two feedback loops comprises the high gain summing amplifier in series with a diode, each summing amplifier comparing the output signal with one of the limit signals. The summing amplifiers insure hard limiting when the output signal tends to exceed the upper or lower limit.

Gain ranging amplifier system

Abstract: The compression portion of an instantaneous companding (compressing-expanding) system includes at least two and preferably four "bi-gain" amplifiers connected in cascade. Each bi-gain amplifier normally has a low-gain state and can be switched to a discrete high-gain state. A discrete reference voltage is provided to compare with the output of each amplifier. The amplifiers are initially switched to their low-gain states and the reference voltage corresponding to the first amplifier is selected. A comparator means makes a comparison between the system's output voltage and the selected reference voltage. The control means switches the first amplifier to its high-gain state or holds it in the low-gain state depending on the result of the comparison. By utilizing a different variable reference voltage and bi-gain amplifiers with two different amplification factors, the number of amplifiers and comparisons is significantly reduced. Noise-cancelling means are also associated with each amplifier to remove undesired DC noise signals from each amplifier.

Programmable binary amplifier

Abstract: A multistage amplifier having an automatically programmable gain is disclosed in which the amplifier gain is incremented in binary steps to a desired level. Each amplifier stage is switchable between a first and second gain in a binary sequence such that the four digit output of a sixteen bit counter will increment the total amplifier gain in sixteen binary steps. A readback and decoding circuit for reading magnetic tape is also disclosed in which the signal amplitude of data read from the magnetic tape is compared to a reference voltage which corresponds to the data readback clipping level. Only amplified data which exceeds the predetermined clipping level is gated out of the circuit for processing. Since input signal amplitude varies from tape to tape and from head to head, the automatic read amplification burst on each tape is used to preset the amplifier gain such that the amplified amplitude of the readback signal is maintained constant as long as the readback signal supplied to the amplifier is within a predetermined range. The amplifier gain is automatically incremented until the amplifier output exceeds the clipping level, thereby insuring that only valid data and not noise or undecodable data are processed.

Digitally controlled amplifying equipment

Abstract: A digitally controllable amplifier unit and musical instrument amplifier incorporating such a unit. Digital control of the transfer function of a high-gain virtual-earth amplifier is effected by switching input and feedback impedances by means of transistor switches. Digital storage means are used to control the transistor switches.

Instabilities in RF-power amplifiers caused by a self-oscillation in the transistor bias network

Abstract: This paper describes a self-oscillation in the bias network of an amplifier which is commonly used for the output stage in mobile transmitters. It is demonstrated how some often observed spurious oscillations may be related to the self-oscillation and a method for stabilizing the amplifier is derived and discussed.

Time division multiplexing amplifier

Abstract: A time division multiplexing amplifier having a differential amplifier, such as a dynamic bridge amplifier, which has a predetermined gain accurately provided by means of operational network resistors. The differential amplifier is used to amplify differential signals containing a common-mode voltage. Prior to amplification of the differential signals, a common-mode voltage is applied in common to two input terminals of the differential amplifier, and then the differential amplifier is adjusted to provide a zero offset voltage. After that, the differential signals are applied to the differential amplifier, so that the differential signals can be amplified without having any adverse effect of a common-mode voltage.

Split-path receiver for fiber optics application

Abstract: A receiver for use with a photodiode in an electro-optical transmission l. First and second amplifier circuit channels are connected to an output port of a photodiode. One channel is provided with a wide-bandwidth amplifier for amplifying the high frequency portion of a signal from said output signal port and a second channel is provided with a low frequency amplifier for amplifying direct current and the low frequency portions of the signal from said output signal port. The outputs of the wide-bandwidth amplifier and the low frequency amplifier are combined to provide a composite output signal which is an amplified replica of the output of said photodiode.

Bidirectional radio frequency amplifier with receiver protection

Abstract: A bidirectional radio frequency amplifier which includes a power amplifier and a receiver amplifier connected to a common antenna. A pair of parallel diodes coupled across the input of the receiver amplifier provides a high impedance path for a received signal and a low impedance path during transmission thereby eliminating the need for mechanical or semiconductor switching.

Protective network for an insulated-gate field-effect (IGFET) differential amplifier

Abstract: The input stage of an amplifier includes two input terminals to which are connected the gates of two, differentially connected, IGFETs protected by two diodes connected back-to-back (in series) between the gates. The amplifier also includes means for applying an external signal source to one input terminal, means for shorting the diode connected to the other input terminal, and means for negatively feeding back the output of the amplifier to its input. This maintains the potential difference across the diode connected to the input terminal to which the external signal source is connected close to zero volt thereby substantially eliminating any leakage current through it.

Two-channel hearing aid system - has HF and LF channels, each containing input filter and AGC amplifier and output filter

Abstract: The hearing-aid has two channels (3, 4) between a microphone (1) and a loudspeaker (21). One channel handles the upper part of the wanted band and the other the lower part. Each channel consist of an input filter (LP or HP), a gain-controlled amplifier (6) and a filter (7, 8) with the same cutoff frequency as the input filter of that channel. The amplifier output is passed via a potentiometer (10) and a second amplifier (11) (followed by a rectifier) to its own gain control input. The advantage lies in each producing output signals of the wanted sub-bandwidth.

Drive control to prevent simultaneous conduction in push-pull switching amplifier

Abstract: A drive circuit responsive to the phase of the amplifier output current eres that the non-conducting amplifier element remains off while the other amplifier element conducts. The output current phase can be detected either from the individual amplifier element outputs or from their combined outputs. Adjustments are made to compensate for any phase shift which occurs between the input to the amplifier and the point in the output at which the phase is detected.

Solid state amplifier

Abstract: An amplifier capable of operation in four modes singly or in combinations is disclosed. The modes are: DC amplification mode, AC amplification mode, suppressed baseline mode, and offset correction mode. In the DC amplification mode, the amplifier operates as a conventional DC amplifier. In the suppressed baseline mode, the outputs of the input and output amplifiers are connected back to their input stages through a long time constant integrator resulting in the suppression of any DC output voltage. In the AC amplification mode an RC decoupling network is inserted in the inputs to the input amplifier means to pass AC signals and reject DC components. In the offset correction mode, the inputs of the input and isolator amplifier means are shorted to create zero differential at the summing junctions thereof. Any offset voltage present at the output of the input amplifier means or output amplifier means is suppressed by means of integrated feedback to the input stage of the input and output amplifier means. The offset correction mode is entered periodically and at the end of the offset correction mode, all connections revert back to their normal condition. The offset correction voltage attained is applied until the next offset correction period at which time new correction values are determined. Additionally, means for accomplishing the above functions are disclosed employing solid state switching, photon coupled isolation, and a floating power supply.

High gain differential amplifier

Abstract: A high gain, field effect transistor differential amplifier including first and second cascade connected inverter stages and a feedback controlled source of current connected to each of the stages. High voltage gain is achieved by virtue of a positive feedback path connected between an output terminal of the differential amplifier and the source of current so that the current in each inverter stage is controlled.

Switching-mode absolute-value amplifier and its applications

Abstract: Proposes methods of absolute-value and variable-phase operations using switching techniques. These methods show high efficiency and characteristics suitable for use in very-low-frequency regions due to its sampling effects. This paper introduces the basic principle, theoretical analysis, and characteristics of the switching-mode absolute-value amplifier and presents the realization of a variable-phase ultra-low-frequency signal generator by means of the switching-mode operations.

Amplifier circuit having integral means for detecting and preventing non-linear operation

Abstract: An amplifier circuit including provision for detecting non-linear circuit operation caused by the application of input signals that exceed either the amplifier dynamic range or the amplifier slewing capability is disclosed. The amplifier circuit includes the cascaded combination of a voltage amplifier stage, a voltage-to-current converter stage, a current limiter stage and an output stage. A first signal, obtained at the junction between a capacitor and resistor that are series connected between the signal common or ground potential and the input terminal to the output stage, is compared with a second signal obtained at the input terminal of the voltage to current converter stage. When the amplifier circuit is operating within the linear region these two signals are of equal magnitude or exhibit some other known relationship to one another. If, however, the amplifier operation is non-linear, due to either the application of an input signal of an amplitude that exceeds the linear dynamic range of the amplifier or due to an applied input signal having a time rate of change that exceeds the amplifier slew rate capability, a detectable increase in the voltage difference between the first and second signals occurs. This detected signal can be utilized for a number of functions including either disconnecting the improper input signal from the amplifier input terminals or conditioning the signal such that it lies within the linear operating range of the amplifier.

Low current drain amplifier system

Abstract: A low current drain amplifier system, adaptable for use in cardiac pacers and other applications requiring low current drain operation, having an amplifier path comprising transconductance amplifier means characterized by having the circuit characteristic of a current source at its output, the transconductance amplifier means direct driving an active circuit having a high impedance input, and a current source supply for maintaining fixed current operation of the amplifier system elements. In the preferred embodiment, the amplifier path contains a first OTA operating as an amplifier of received signals, the first OTA having its output direct coupled to an input of a second OTA which operates as a comparator, the output of the comparator OTA being direct connected to an IC transistor element.

Feed-forward amplifier with simple resistive coupling

Abstract: Feedback amplifiers having zero or infinite input and output impedances are used as the main amplifier and error amplifier elements of a feed-forward amplifier system. This allows the required impedance matching with simple resistive coupling networks rather than the complicated couplers heretofore required. The use of both series and shunt feedback provides convenient coupling points for the proper phase relationship between combining signals, and the unidirectional conductivity of the amplifier transistors supplies the directionality usually required of the couplers.

Amplifier for receive mode operation

Abstract: An amplifier circuit to be interposed between an antenna and a utilization unit such as a radio, scanner, citizens band transceiver or the like. The amplifier circuit includes a current divider for dividing incoming signals into first and second parallel paths and a current amplifier including a pair of cascaded transistors to receive and amplify signals in said second path. The signals in the first path are passed to the utilization unit without amplification. A sensing network is provided to bypass the current divider and the amplifier when the utilization unit is transmitting signals.

Amplifier with gain control means

Abstract: A gain controllable amplifier of the present invention comprises a first and a second differential amplifier. The first differential amplifier serves as an amplifier for an input signal to be impressed on emitters connected in common with each other, while the second differential amplifier serves as a base bias voltage control circuit of the first differential amplifier. The bias voltage derived from the second differential amplifier is changed by a D.C. bias voltage applied to the bases of the respective transistors in the second differential amplifier. The connected to the respective output terminals of the second differential amplifier are transistors whose bases receive a constant voltage. The gain of the first differential amplifier can be controlled by adjusting the D.C. bias voltage applied to the second differential amplifier. The present invention further comprises two current supply circuit each connected to the aforesaid respective output terminals of the second differential amplifier. When one of the transistors in the second differential amplifier is brought into a cut-off condition, the base bias voltage on the first differential amplifier is supplied directly through a current supply circuit. As a result, a variable range of the base voltage on the second differential amplifier is becomes wider, with a resulting increase in the gain control range of the first differential amplifier, thereby achieving increased attenuation of gain. The amplifier according to the present invention is suited for use as a gain control circuit especially for an audio circuit which requires attenuation to a great degree.

Parallel power amplifier circuits

Abstract: A plurality of similar power amplifier circuits are connected in parallel in the output of an amplifier between the amplifier's voltage amplifier circuit and the load. Each of these amplifier circuits has a similar ballasting resistor connected between its output and the load. The amplifier circuits have unity closed loop voltage gain. The value of the ballasting resistors is empirically chosen such that these resistors are capable of accommodating differences in the outputs of the amplifier circuits which may occur, such that the load is equally shared between the amplifier circuits.

Shutter operating circuits for photographic cameras

Abstract: In a shutter operating circuit wherein the shutter time is controlled by a photoelectric transducer disposed to receive the light transmitting through the objective lens, there are provided a first amplifier for amplifying the output from the photoelectric transducer, a second amplifier having a high input impedance and operating to generate an output corresponding to the output from the first amplifier, means for feeding back the output from the second amplifier to the input of the first amplifier, a capacitor connected on the input side of the second amplifier for holding the output from the first amplifier in accordance with the opening operation of the shutter of the camera, a first impedance element connected in series with the photoelectric transducer, a second impedance element connected in parallel with the series combination of the first impedance element and the photoelectric transducer, an integrating capacitor for integrating the output from the second amplifier in accordance with the opening operation of the shutter, and a shutter trigger circuit for closing the shutter when the voltage across the integrating capacitor reaches a predetermined .[.valve.]. .Iadd.value .Iaddend.whereby the exposure time is determined by the output current from the second amplifier.

Three-phase SCR drive circuit using an opto-coupled pulse amplifier

Abstract: A three-phase shift network includes a single transistor which controls phase shift by introducing a variable resistance into the network as determined by a D.C. control signal supplied to the transistor. The three-phase signals generated from the phase shift network undergo pulse shaping and are subsequently introduced into an opto-coupled pulse amplifier. The amplifier drives large SCR devices, connected as a load.

Chrominance amplifier control circuit providing simultaneous adjustment of gain and DC level

Abstract: In a circuit for setting a chrominance signal controlling the emission of an electron beam in the picture tube of a color television receiver, the circuit including an amplifier connected to amplify the chrominance signal, with the output of the amplifier being held at a constant voltage level during each horizontal line blanking period by means of a keying pulse, and in which the amplifier is provided with a feedback path including an amplification determining resistance network, keying pulses are fed into the resistance network in such a manner that variation of the resistance presented by the network produces a simultaneous change in the gain of the amplifier and the direct voltage level of the chrominance signal at the output of the amplifier.