Showing papers on "Cascade amplifier published in 1987"

A differential switched-capacitor amplifier

Abstract: A monolithic realization of a switched-capacitor amplifier is reported. It has op-amp offset voltage cancellation without requiring the output to slew to ground each time the amplifier is reset. The amplifier is very insensitive to low op-amp gain. It also has clock-feedthrough cancellation. Finally, it can be used as a differential amplifier with both inputs being sampled at the same instance.

Programmable band-pass amplifier for use with implantable medical device

Abstract: A switched-capacitor, band-pass, programmable amplifier is used as a sense amplifier in an implantable cardiac pacemaker. Switching means are used to switchably connect various capacitors to the same amplifier circuits. Clock generator means are used to generate clock signals that are used to control the rate at which the switching means operates. By programmably selecting the switching rate to be a desired value, the band-pass characteristics and gain of the sense amplifier may be varied. When a pacemaker stimulation pulse occurs, the band-pass characteristics and/or gain of the sense amplifier, may also be automatically varied to improve amplifier recovery time. The rate at which the capacitors are switchably connected to the amplifier circuits, may be selected remotely, thereby allowing the band-pass characteristics to be programmable.

Switchable mode amplifier for wide dynamic range

Abstract: There is disclosed an amplifier device for use with a photodetector for amplifying wave energy signals received by the photodetector and converted into electrical signals. The amplifier device includes a first amplifier having its input connected to a junction between the photodetector and first and second photodetector load impedances. A negative feedback amplifier is connected to the output of the first amplifier. The negative feedback amplifier provides a feedback voltage to the first load impedance when in its first mode of operation and effectively reduces the voltage feedback to the first load impedance when in its second mode of operation. A switching device is provided to effectively switch the second load impedance in and out of circuit with the photodetector to effectively change the photodetector load impedance and alter the bias voltage to the feedback amplifier. As, a consequence, the feedback amplifier is able to operate in either of its first or second modes of operation respectively switching the amplifier device from a good sensitivity, broad bandwidth transimpedance amplifier to a follower amplifier of improved dynamic range.

Fast latching flip-flop

Abstract: A fast latching flip-flop has a transparent latch master section with an input amplifier, an output latch, a current source connected to provide current for the input amplifier and the output latch, and a switch for applying the current from the current source to either the input amplifier or the output latch. A slave section is connected to the output latch to transfer the data from the output latch to the output of the fast latching flip-flop. A delay transistor is inserted between the switch and the input amplifier to add delay in the turn-off of the input amplifier. Additional delay is attained by connecting a plurality of diode-connected transistors to the junction of the delay transistor and the switch. The result is a reduction of the metastable region between the turn-off of the input amplifier and the turn-on of the output latch.

MMIC (monolithic microwave integrated circuit) low noise amplifier

Abstract: The invention relates to a low noise amplifier for use at microwave frequencies which may be fabricated using integrated circuit techniques. In accordance with the invention, critical components are made adjustable so as to simplify the design process and manufacturability of the amplifier. A two stage low noise amplifier is disclosed in which TEE networks are used as input and output networks in each stage, and in which one element of each TEE includes an adjustable spiral inductor. The value of each adjustable spiral inductor may be adjusted by removal of one or more air bridges disposed along the inner turn of the inductor. This permits one to "tune" the amplifier and optimize its performance.

Adaptive gain control amplifier

Abstract: An adaptive gain control amplifier (12) is described in relation to an audio system for adjusting output volume of a loudspeaker (16) automatically in response to an interference signal (21) such as background noise The amplifier (12) includes a divider circuit (30) which computes the ratio of a time average of a corrupted signal (20, 21) which is a combination of a controlled output signal (20) and the interference signal (21), to produce a control voltage which controls the gain of the amplifier To reduce the dynamic range of the quotient of the ratio the divider circuit (30) incorporates a logarithmic ratio circuit The circuitry of the amplifier includes a ''sensing channel'' and a ''reference channel'' for extraction of the above averages of the corrupted signal and controlled output signal, respectively A method is also claimed

Instrumentation amplifier arrangement

Abstract: A substantially zero average DC output voltage is obtained in an instrumentation amplifier without degrading the gain by detecting the output of the amplifier and operating a non-galvanically coupled device responsive to the detected output to apply feedback to the amplifier for balancing out common mode output voltages.

Intermediate frequency amplification circuit capable of detecting a field strength with low electric power

Abstract: In an intermediate frequency amplification circuit comprising first through n-th differential amplifiers which are connected in cascade to one another with the first amplifier supplied with a circuit input signal and which successively produce amplifier output signals with an n-th amplifier output signal produced as a circuit output signal from the n-th amplifier, first through (n+1)-th rectification circuits are supplied with the respective amplifier output signals with the circuit input signal given to the first rectification circuit. Each rectification circuit comprises a differential unit comprising at least one pair of transistors have different emitter areas from each other to rectify each amplifier output signal and to produce a collector current which is summed up by an adder circuit to be produced as a field strength signal. The rectification circuits may carry out either half-wave rectification or full-wave rectification. A plurality of the above-mentioned pairs may be included in each rectification circuit.

Low 1/f noise amplifier for CCD imagers

Abstract: A low 1/f noise amplifier has been provided for an output of a CCD imager. To reduce clock noise, the amplifier employs a differential detection scheme. Linear stages (54, 76) are coupled by capacitors (60, 82) to a differential amplifier (64). Differential amplifier (64) employs a first (112, 118) and a second (172, 198) differential transistor pair. The second differential pair (172, 198) is cross-coupled to the outputs of the first differential pair (112, 118) by load resistances (180, 206) with the voltage drop across them remaining substantially constant. To maintain stability, the positive and negative branches of the amplifier are periodically reset by a resetter (210). The input nodes (62, 86) are periodically reset to a voltage reference.

Power limiting audio amplifier temperature protection circuit

Abstract: An audio amplifier of the type including circuitry to detect clipping and adjust the gain of an amplifier input element to control the clipping in closed loop operation further includes circuitry effective to sense the temperature of an amplifier component and change the amplifier bias voltage that determines the maximum non-clipping voltage so as to induce clipping in the amplifier when the temperature exceeds a predetermined temperature. The clipping control circuitry then reduces the input gain to the amplifier to control the clipping and, in so doing, reduces power dissipation to a level allowing the temperature to decrease to the predetermined temperature. The circuit provides for closed loop control of amplifier temperature in marginal temperature situations with minimal intrusion on the music reproduction process.

High speed serial input/output semiconductor memory

Abstract: A pseudo static RAM having a function which enables high-speed serial read and write operations with a relatively simple circuit configuration. In the stage subsequent to an amplifier for amplifying read signals from memory cells which are output to complementary common data lines, there are provided a first flip-flop for transmitting the output signal from the amplifier to an output buffer in an ordinary read operation, a second flip-flop connected between the amplifier and the first flip-flop in a serial read operation so as to transmit the output signal from the amplifier to the output buffer in cooperation with the first flip-flop, and an address counter for successively selecting a plurality of data lines.

Microwave temperature compensated cascadable amplifier for fiber optical receiver

Abstract: A temperature compensated amplifier network for a fiber optical receiver includes a photodiode having an optical input and a current output, and a cascadable transimpedance amplifier having N stages, each stage having a common base-emitter voltage. An emitter-follower transistor is coupled to the last stage of the transimpedance amplifier network and has a base-emitter voltage of the same magnitude but of opposite polarity from the base-emitter voltage of each of the amplifier stages. Any DC drift of the amplifier stages is therefore offset by a compensating drift in the opposite direction by the output emitter-follower.

Amplifier with D.C. compensation

Abstract: A circuit for providing DC bootstrapping to an AC amplifier integrates a sample of the output of the amplifier and feeds the result of that integration to the input of the amplifier, thereby driving the input of the amplifier to a zero potential level. The integration can be accomplished by an operator amplifier and a capacitor in a feedback circuit.

Wideband microwave matrix amplifier

Abstract: A microwave amplifier that both multiplicatively and additively amplifies microwave frequency signals. The amplifier, herein coined a matrix amplifier, is a distributed amplifier with two or more tiers (rows) of transistors. Each tier has a plurality of transistors which additively amplify the signal entering that row of the amplifier, and each row multiplicatively amplifies the output of the previous row. The gates of the transistors in each row are sequentially coupled to an input transmission line having a series of transmission elements. The outputs of all the transistors from each row are sequentially coupled to the input transmission line of the next tier, except that the outputs of the last tier are coupled to an output transmission line for transmitting the output of the amplifier to an output node. Furthermore, each transmission lines has (1) at least one line termination at one of its ends for absorbing signals incident on that end of the transmission line, and (2) biasing means for d.c. biasing the transmission line at a corresponding voltage potential.

Linearized differential amplifier

Abstract: A linearized differential amplifier having two feedback paths. One of the feedback paths functions to linearize the output of the differential amplifier. The remaining feedback path functions to slightly limit the operating range of the differential amplifier to ensure the operational stability of the differential amplifier.

Linearity control circuit for digital to analog converter

Abstract: In a circuit utilizing a digital to analog converter, an amplifier receives two voltage levels of a digitally modulated input signal via two different switching circuits. Linearity of output signals provided by the amplifier is significantly improved by a circuit for effectively matching the resistances provided by the two switching circuits to the amplifier. A feedback circuit from the output of the amplifier, including a feedback amplifier, is used to withdraw from a switching device any current passing therethrough when ON, thus eliminating any effect of resistance of the switching device from the amplifier.

Low-frequency power amplifier, in particular of the integrated type

Abstract: The low-frequency integrated amplifier comprises a voltage amplifier stage and two power amplifier stages including power amplifier means driven by the voltage amplifier stage and fedback by means of a respective feedback network dimensioned so that, at the frequency at which the phase shift of the power stages exceeds 180°, the open loop gain thereof is less than 0 dB, so as to prevent, for any kind of load and for every output voltage, any oscillation of said stages, and ensure the absolute stability of the system.

Sense amplifier with bit-line derived clocking

Abstract: A sense amplifier device, as of CMOS technology includes a first (AN) and second (AP) amplifier responsive to the voltages (VB0, VB1) of two bit lines (B0, B1) to be amplified. When it is activated, the first amplifier (AN) connects the bit line having the lowest potential to ground potential. When the voltage of one of the bit lines is lower than a threshold voltage (VT), the second amplifier is triggered and connects the bit line having the highest potential to supply voltage.

Bridge amplifier operating from an asymmetrical power supply

Abstract: A fully integratable bridge amplifier comprises two identical amplifiers (1; 5) each being provided with a first input stage (20; 40) whose inputs constitute the first non-inverting inputs (2; 6) and the first inverting inputs (3; 7) of the amplifier, a second input stage (29; 50) whose inputs constitute the second non-inverting inputs (28; 49) and the second inverting inputs (27; 48) of the amplifier, and an output stage (25; 45). The first inverting input (3; 7) of each amplifier (1; 5) is connected to the output (12) of a buffer amplifier (9) via a first resistor (R 6 ; R 9 ) which together with a second resistor (R 5 ; R 8 ) constitutes a negative feedback network between the output (4; 8) of the amplifier (1; 5) and the first inverting input (3; 7). The first non-inverting input (2; 6) is also connected to the output (12) of the buffer amplifier (9). This output (12) and consequently the first inputs (2, 3; 6, 7) of the amplifiers (1; 5) are at half the supply voltage with respect to the d.c. voltage, which is obtained by voltage division (R 2 , R 3 ) of the supply voltage between the positive supply terminal (15) and ground terminal (16), while with respect to the signals this output (12) constitutes a virtual ground connection. The second non-inverting inputs (28; 49) and inverting inputs (27; 48) are at a reference voltage (V ref ) with respect to the d.c. voltage. The input voltage V i is directly applied to the second non-inverting input (28) of the first amplifier (1) and the second inverting input (48) of the second amplifier.

RF-AM transmitter with pulse width modulator

Abstract: An RF-AM transmitter includes a pulse amplifier responsive to a pulse width modulated (PWM) signal derived in response to an information signal. A low pass filter converts pulses derived by the power amplifier into a variable amplitude signal that is DC coupled to a power supply for an RF amplifier. An amplifier system including the pulse and RF amplifiers has stray capacitance coupled to a modulator which derives the PWM signal; the stray capacitance lengthens narrow modulator output pulses so they are excessively long. The amplitude of only the narrow pulses is reduced by a resistor-capacitor timing circuit in series with a switch to substantially preserve the narrow pulse area. The switch provides a low impedance path from the timing circuit to a reference potential terminal when current initially flows in the circuit during pulse transitions and throughout the length of each of the short duration pulses. Thereby, the power amplifier is forward biased but not driven into saturation during the short duration pulses. The switch provides a higher impedance path from the timing circuit to the reference potential terminal after the transition has elapsed, enabling the power amplifier to be saturated during pulses longer than the short duration pulses. The RF power amplifier tube has a tendency to load the power amplifier tube out of saturation during wide pulses. The ampitude of the wide pulses is maintained substantially constant by a resistor shunted by an inductor between the modulator and the power amplifier.

Self-test device and method having an amplifier converted into an oscillator

Abstract: An FM receiver is self tested by connecting a positive feedback network in circuit with a wideband, front end rf amplifier of the receiver, so that the amplifier is converted into an oscillator Rf and if characteristics of the receiver are determined by comparing the amplitude of an if signal with a predetermined reference value while the amplifier is converted to an oscillator Noise characteristics of the receiver are determined by comparing the amplitude of an audio frequency signal of the receiver with a predetermined value while the amplifier is converted to an oscillator and the amplifier derives an unmodulated rf output Baseband characteristics of the receiver are determined by varying a reactance in the positive feedback path to impose FM on rf oscillations derived by the amplifier and by comparing the amplitude of the output of the audio frequency amplifier with a predetermined value By varying the value of the reactance in the feedback loop, the oscillating frequency is swept to determine the center operating frequency and if bandwidth of the rf, amplifier

A precision power amplifier for power/energy calibration applications

Abstract: A precision power amplifier for use in power/energy calibration applications is described. The amplifier was primarily designed to boost the output amplitude of a digital generator to provide the nominal 120- or 240-rms voltage component of a “phantom” calibration power source. The amplifier has a fixed gain of 40 and can provide a maximum output voltage swing of 970 V peak-to-peak or 340-V rms at 100-mA rms. The bandwidth is from dc to 150 kHz and at 60 Hz the observed no-load short-term amplitude and phase instabilities are ±5 ppm and ±5 μrad, respectively. The amplifier design uses high-voltage N-channel MOSFET's in the output driver stage together with a unique circuit topology of opto-isolators between the low-level input stage and the high-level output stage.

Amplifying circuit arrangement

Abstract: A robust amplifier consists of two delay lines 12 and 23 linked by a number of discrete amplifiers 13. Distortion correction is carried out by distortion feed forward. This is achieved by sampling the output of each amplifier 13 at a coupler 17 and then subtracting this sample from the input signal to later amplifiers (13) along the delay line 12 at directional coupler 19. As a result each discrete amplifier's distortion is corrected by all of the following discrete amplifiers (13) in the amplifying circuit.

Cascode amplifier with nonlinearity correction and improve transient response

Abstract: An improved cascomp amplifier includes a main differential transconductance amplifier stage, a pair of diode connected sense transistors and a differential correction amplifier stage. The sense transistors present a precise measure of the error voltage to the correction amplifier and extend the reverse breakdown voltage of the input stage of the main amplifier. The sense transistors are also used to correct additional gain variations due to transistor beta. The correction amplifier provides a current which cancels the nonlinearities of the main amplifier. The configuration of the correction amplifier reduces the capacitive load to the main amplifier thereby reducing aberrations in the transient response.

Multi-output feedback amplifier

Abstract: A feedback amplifier for providing an amplified signal to first and second utilization networks includes first and second feedback paths. The amplifier output is coupled via a first coupling resistor to a first terminal to which the first utilization network is connected, and via a second coupling resistor to a second terminal to which the second utilization network is subject to being connected. The first feedback path couples the amplifier output to the amplifier input exclusive of the first coupling resistor. The second feedback path couples the amplifier output to the amplifier input and includes the second coupling resistor. The amplifier output signal remains substantially constant in the presence or absence of said second utilization network.

Digital amplifier configuration in integrated circuits

Abstract: A digital amplifier configuration in integrated circuits for the amplification of a voltage change includes a digital amplifier. The digital amplifier couples pairs of bit lines extended beyond the permissible capacity thereof to extensions of the pairs of bit lines.

Linearized differential fT doubler amplifier

Abstract: An improved differential f T doubler amplifier is provided having two error amplifiers in series connection with the main signal amplifier for cancelling the nonlinear currents generated by the main signal amplifier. The error amplifiers receive a differential error voltage provided by a pair of transistors which sense the error voltage in the main signal amplifier.

Circuit for a sensor

Abstract: In a circuit for a sensor the output signal of which is dependent not only on the variable to be determined but also on the temperature, an amplifier having a temperture-dependent amplification factor is connected to the output of the sensor, and the output of the amplifier is connected to an adder circuit to which a temperature-dependent voltage can be fed. The amplifier is preferably a differential amplifier within the feedback branch of which a temperature-dependent resistor is inserted. The adder circuit is preferably formed by another differential amplifier to the inputs of which the output signal of the differential amplifier with temperature-dependent amplification, the temperature-dependent voltage and a substantially temperature-independent voltage can be fed via resistors.

Three wire amplifier circuit with diagnostic capabilities

Abstract: A three wire amplifier circuit for use with a sensor in which the amplifier output drives the negative supply so that the negative supply becomes the circuit output and the system is capable of diagnosing the condition of the sensor.

Amplifier for amplifying input signal voltage and supplying the same

Abstract: An amplifier comprises a first amplifier circuit and a second amplifier circuit. An input signal voltage and an input DC bias voltage are applied to the first amplifier circuit, and an input DC bias voltage is applied to the second amplifier circuit. The input DC bias voltages applied to the first amplifier circuit and the second amplifier circuit are common to each other. Output bias voltages of the first amplifier circuit and the second amplifier circuit become equal to each other. The amplified signal voltages are applied to a load connected between outputs of the amplifier circuits.