Abstract: Two variations of a continuous-time instantaneous companding filter are integrated in a 25 GHz bipolar process. Their −3 dB frequencies are tunable in the ranges of 1-30 MHz and 30-100 MHz. The dc gains are controllable up to 10 dB. The measured dynamic ranges for a 1% total harmonic distorsion are 62.5 dB and 50 dB, for the 30 MHz and 100 MHz filters respectively. At maximum cutoff frequencies, the filters dissipate 6.5 mW from a 1.2 V supply. The filters are simple, common-mode interference-resistant, class AB log-domain integrators, suitable for implementation in low-cost bipolar processes. They are suitable for realizing low-voltage filters with reasonable linearity and signal-to-noise ratio. ALL-NPN low distortion input and output interface stages can be added to the integrators. The filters can be used to realized high-frequency programmable filters.

Abstract: A method and apparatus is disclosed for providing highly linear resistance with high sheet values, and for implementing resistors in a conventional CMOS process when either drain or source must operate near the rail of a circuit. Accordingly, a five terminal distributed MOS resistor device includes a drain terminal, a source terminal, and a channel region disposed between the drain terminal and the source terminal. A bulk terminal is adjacent the channel region. A first gate terminal is adjacent the source terminal and a second gate terminal is adjacent the drain terminal. Lastly, a gate region of resistive material is disposed between the first gate terminal and the second gate terminal, wherein upon application of a voltage to the first gate terminal and the second gate terminal, a voltage drop across the gate region is equally distributed along a length of an electrical channel in the channel region.

Abstract: A high-frequency composite component can achieve reduction in size and weight, while providing high performance. A portable wireless device incorporates the high-frequency composite component, including a multi-layer substrate, with a low noise amplifier LNA and a band pass filter BPF constituting parts of a high-frequency circuit, with an input terminal, an output terminal, and control terminals on the substrate. The low noise amplifier LNA is constituted of transistors, an inductor, capacitors, and resistors. The band pass filter BPF is constituted of strip lines, an inductor, and capacitors. The low noise amplifier LNA and the band pass filter BPF are connected with each other within the substrate via a matching capacitor. The amplifier ground and filter ground are separated within the substrate and connected respectively to separate ground terminals on the substrate.

Abstract: A filter circuit uses a trans-conductor circuit coupled to a control circuit having similar characteristics as the trans-conductor circuit. The control circuit is used to set and/or control the quiescent voltage of the trans-conductor circuit. As a result, the trans-conductor circuit may be designed to operate across a large frequency range while consuming minimal power. The control circuit may be operated using direct current (dc) voltage and may be implemented similar to the trans-conductor circuit implemented in the filter circuit.

Abstract: When an input signal to be amplified is very small and a large blocking signal having a high frequency is included in an input, it is necessary for a filter for mobile communication for removing thereof that a common-mode signal rejection ratio is large. Further, even in the case of an amplifier having a high gain, it is preferable that the common-mode rejection ratio is large in order to avoid saturation of the amplifier by noise. A common-mode rejecting characteristic is added to an input stage by making transconductance circuits of an input of an integrating circuit proposed by Nauta differential circuits and connecting thereof in cross connection. Thereby, a filter as well as an amplifier improving the common-mode rejection ratio of a total, are realized by being applied to a CMOS process or a BiCMOS process.

Abstract: A filter circuit uses a trans-conductor circuit coupled to a control circuit having similar characteristics as the trans-conductor circuit. The control circuit is used to set and/or control the quiescent voltage of the trans-conductor circuit. As a result, the trans-conductor circuit may be designed to operate across a large frequency range while consuming minimal power. The control circuit may be operated using direct current (dc) voltage and may be implemented similar to the trans-conductor circuit implemented in the filter circuit.

Abstract: An operational amplifier having a low impedance input and a high current gain output. The operational amplifier comprises: 1) a first N-channel transistor having a source coupled to the low impedance input of the operational amplifier; 2) a first constant current source coupled between the source of the first N-channel transistor and ground; 3) a first amplifier stage having an input coupled to the first N-channel transistor source and an inverting output coupled to a gate of the first N-channel transistor; 4) a second amplifier stage having an input coupled to a drain of the first N-channel transistor and an output coupled to the high current gain output of the operational amplifier; and 5) an internal compensation capacitor coupled between the input and the output of the second amplifier stage.

Abstract: A transconductance amplifier and method for improving the phase response and linearity. A differential amplifier circuit receives differential signals for amplification on respective bases of input bipolar transistors. The transistors amplify a small signal received on the based connections to produce an amplified output current. The differential amplifier circuit is connected to load impedances which form a cascode transconductance amplifier output stage. Feedback transistors provide a feedback voltage from the emitters of each of the different bipolar transistors to the base, improving the linearity of the differential amplifier. Phase compensation is provided by cross coupling through first and second capacitors a portion of each individual differential signal component to the base connections of the differential amplifier input transistor.

Abstract: A low-corner frequency high pass filter circuit (10) includes an operational amplifier (12). The operational amplifier (12) has an inverting input (14) and a non-inverting input (24). A series capacitor (26) has a first end connected to the non-inverting input (24) of the operational amplifier (12). A second end of the series capacitor (26) is connected to an input signal (28). A low gain amplifier (30) has an input connected to an output (22) of the operational amplifier (12) and has an output (32) connected to the non-inverting input (24) of the operational amplifier (12). The low gain amplifier (30) performs the function of large value resistor.

Abstract: A high-output amplifier (1), having a high gain, (2) having a high efficiency, (3) less affected by temperature changes, (4) operative linearly in output levels over a wide dynamic range and (5) using a control voltage, comprises a transistor amplifier, and a bias circuit having first and second bias circuits. A first transistor provided in the first bias circuit has a first terminal and a control terminal that are short-circuited and connected to a control source as a first high-voltage-side source and to a control circuit of the transistor amplifier, and a second terminal connected to a low-voltage-side source. A second transistor provided in the second bias circuit has a control terminal connected to the control source, a first terminal connected to the second high-voltage-side source, and a second terminal connected to the control terminal of the transistor amplifier.

Abstract: A large-time-constant microphone filter which contains resistance and capacitance as its constituent and can be formed in the same semiconductor chip as a microphone unit is achieved, which results in downsizing and cost reduction of the microphone unit. A transistor of a current mirror circuit is used as a resistance of a microphone filter, utilizing a differential resistance produced by a channel length modulation effect of the transistor or an Early effect. When variations in the drain-source voltage of the transistor occur, the drain-source current of the transistor slightly varies in linear characteristics and the transistor serves a high value of resistance. Being a current mirror circuit, the microphone filter is resistant to characteristic variations due to temperature changes and can be formed in a semiconductor chip without a significant increase in chip area.

Abstract: A tunable differential amplifier includes an amplifier circuit, a current mirror, a dynamic current regulator, and a dynamic output common mode regulator. The current mirror is operably coupled to the amplifier circuit and controls the current flowing through each leg of the amplifier circuit. The current through the current mirror is established based on a regulated current provided by the dynamic current regulator and a common mode error current signal provided by the dynamic output common mode regulator. The common mode error signal is representative of an error between the desired output common mode of the amplifier circuit and the actual common mode of the output of the amplifier circuit. The regulated current is based on the common mode of the input of the amplifier circuit. As such, the biasing current and the common mode output of the differential amplifier is dynamically regulated.

Abstract: A low power analog equalizer is disclosed that provides up to twenty decibels (20 dB) of alternating current gain in a single stage of analog signal equalization. The analog equalizer comprises an operational amplifier coupled to two half circuits. Each half circuit comprises an impedance network capable of receiving an analog input voltage and generating a current signal that is inversely proportional to frequency, a variable resistor capable of adjusting the gain of the operational amplifier, and a transistor and an amplifier coupled in a cascode configuration to create a low impedance node at the output of the impedance network. The analog equalizer is fabricated with 0.18 micron CMOS technology and operates at 1.8 volts.

Abstract: When an input signal to be amplified is very small and a large blocking signal having a high frequency is included in an input, it is necessary for a filter for mobile communication for removing thereof that a common-mode signal rejection ratio is large. Further, even in the case of an amplifier having a high gain, it is preferable that the common-mode rejection ratio is large in order to avoid saturation of the amplifier by noise. A common-mode rejecting characteristic is added to an input stage by making transconductance circuits of an input of an integrating circuit proposed by Nauta differential circits and connecting thereof in cross connection. Thereby, a filter as well as an amplifier improving the common-mode rejection ratio of a total, are realized by being applied to a CMOS process or a BiCMOS process.

Abstract: A low-corner frequency high pass filter circuit (10) includes an operational amplifier (12). The operational amplifier (12) has an inverting input (14) and a non-inverting input (24). A series capacitor (26) has a first end connected to the non-inverting input (24) of the operational amplifier (12). A second end of the series capacitor (26) is connected to an input signal (28). A low gain amplifier (30) has an input connected to an output (22) of the operational amplifier (12) and has an output (32) connected to the non-inverting input (24) of the operational amplifier (12). The low gain amplifier (30) performs the function of large value resistor.

Abstract: A monolithic active frequency selection circuit includes an input presenting a frequency-dependent impedance and a first gain block configured to provide less than unity voltage gain, a high input impedance and a low output impedance. An output of the first amplifier is coupled to the frequency selection circuit input. The frequency selection circuit includes a first phase shifter that, in one aspect, is formed by a first capacitor coupled between the first port and a reference voltage. The frequency selection circuit also includes a second amplifier configured to provide greater than unity voltage gain. The second amplifier has an input coupled to the output of the first amplifier and an output coupled to the input of the first amplifier. The frequency selection circuit further includes a second phase shifter, which may be formed from a capacitor coupled between the output of the second amplifier and a reference voltage.

Abstract: It is an object of the present invention to disclose a fully differential OTA. The active loads in the two output branches of the OTA show high conductance at low frequency and low conductance at higher frequency. In this way an OTA is constructed with inherent pass-band. Low frequencies are amplified little or even filtered out. The amplification of input referred offset voltage due to mismatches in transistor pairs is similarly reduced. Complementary, in another embodiment of the invention the OTA is of the low-pass type, i.e. also amplifying DC signals. Both OTA's are very compact and the common mode output voltage regulation is in both cases part of the active load structure.

Abstract: A monolithic active frequency selection circuit includes an input presenting a frequency-dependent impedance and a first gain block configured to provide less than unity voltage gain, a high input impedance and a low output impedance. An output of the first amplifier is coupled to the frequency selection circuit input. The frequency selection circuit includes a first phase shifter that, in one aspect, is formed by a first capacitor coupled between the first port and a reference voltage. The frequency selection circuit also includes a second amplifier configured to provide greater than unity voltage gain. The second amplifier has an input coupled to the output of the first amplifier and an output coupled to the input of the first amplifier. The frequency selection circuit further includes a second phase shifter, which may be formed from a capacitor coupled between the output of the second amplifier and a reference voltage.

Abstract: A monolithic active frequency selection circuit includes an input presenting a frequency-dependent impedance and a first gain block configured to provide less than unity voltage gain, a high input impedance and a low output impedance. An output of the first amplifier is coupled to the frequency selection circuit input. The frequency selection circuit includes a first phase shifter that, in one aspect, is formed by a first capacitor coupled between the first port and a reference voltage. The frequency selection circuit also includes a second amplifier configured to provide greater than unity voltage gain. The second amplifier has an input coupled to the output of the first amplifier and an output coupled to the input of the first amplifier. The frequency selection circuit further includes a second phase shifter, which may be formed from a capacitor coupled between the output of the second amplifier and a reference voltage.

Abstract: A variable bandpass filter system passes a selected range of frequencies while rejecting other frequencies in an RF input signal. The system includes a switch and an oscillator. The switch receives the RF input signal and an oscillating calibration signal, and passes the RF input signal or said oscillating calibration signal based on a control signal. The oscillator receives an output of the switch, and frequency and gain control signals. The frequency control signal selects an operating frequency of the oscillator, such that the operating frequency determines a range of frequencies to pass. The gain control signal selects gain of the oscillator, where the oscillating calibration signal allows the oscillator to be calibrated by varying the gain such that the oscillator acts as a filter.

Abstract: Resonator comprising first and second balanced integrators (I1, I2) each composed with a balanced amplifier and having a non-inverting (in+) and an inverting (in−) input terminal, as well as a non-inverting (out+) and an inverting (out−) output terminal. First and second coupling circuits (Y1, Y2) are interconnected between the non-inverting output terminal (out+) of the first integrator (I1) and the non-inverting input terminal (in+) of the second integrator (I2) and between the inverting output terminal (out−) of the first integrator (I1) and the inverting input terminal (in-) of the second integrator (I2) respectively.

Abstract: A linear gain control amplifier includes a compensation circuit receiving an external loop control output, outputs a compensation signal approximated to an exponential function thereof, and is implemented in a standard CMOS process. A first amplifier amplifies an input signal in accordance with the compensation signal, a frequency compensation circuit compensates the phase shift of the first amplifier, a second amplifier amplifies an output of the frequency compensation circuit in accordance with the compensation signal, and a tank circuit is connected with the output terminal of the second amplifier to obtain a gain linearity as is required for a mobile communication terminal and a wide variable gain control range.

Abstract: A monolithic active frequency selection circuit includes an input presenting a frequency-dependent impedance and a first gain block configured to provide less than unity voltage gain, a high input impedance and a low output impedance. An output of the first amplifier is coupled to the frequency selection circuit input. The frequency selection circuit includes a first phase shifter that, in one aspect, is formed by a first capacitor coupled between the first port and a reference voltage. The frequency selection circuit also includes a second amplifier configured to provide greater than unity voltage gain. The second amplifier has an input coupled to the output of the first amplifier and an output coupled to the input of the first amplifier. The frequency selection circuit further includes a second phase shifter, which may be formed from a capacitor coupled between the output of the second amplifier and a reference voltage.

Abstract: A semiconductor integrated circuit device comprises a multiple-stage amplifier including a plurality of transistors. The multiple-stage amplifier has a first stage comprising a plurality of bipolar transistors each having a single emitter structure. The bipolar transistors are connected parallel to each other. The semiconductor integrated circuit device can easily be designed, is of a self-aligned structure, and has a single transistor size. The semiconductor integrated circuit device may be used as a low-noise, high-power-gain high-frequency amplifier.

Abstract: Resonator comprising first and second balanced integrators (I1, I2) each composed with a balanced amplifier and having a non-inverting (in+) and an inverting (in−) input terminal, as well as a non-inverting (out+) and an inverting (out−) output terminal. First and second coupling circuits (Y1, Y2) are interconnected between the non-inverting output terminal (out+) of the first integrator (I1) and the non-inverting input terminal (in+) of the second integrator (I2) and between the inverting output terminal (out−) of the first integrator (I1) and the inverting input terminal (in−) of the second integrator (I2) respectively.

Abstract: A high-pass filter has a variable resistance which can be varied by a trimming signal and a programming signal. The variable resistance has a common resistance which is controlled by the trimming signal or the programming signal through a common control line.

Abstract: A filter circuit is provided that provides an input impedance arrangement with a high impedance value, which can be fabricated on a semiconductor body with a high accuracy and with a minimal semiconductor area being required. The input impedance arrangement comprises at least one T network having at least three impedance branches, of which a first impedance branch is connected to the filter input, a second impedance branch is connected to the amplifier input and a third impedance branch is connected to a circuit point for draining a current from the filter input.

Abstract: An automatic cut-off frequency adjustment circuit includes n analog switches and n capacitors, each having a different capacitance, connected to respective ones of the n analog switches. The n analog switches are connected to an output terminal of a first operation transconductance amplifier (OTA). Further, the adjustment circuit includes m analog switches and m capacitors, each having a different capacitance, connected to respective ones of m analog switches. The m analog switches are connected to an output terminal of a second OTA. By turning ON one of the n analog switches connected to the first OTA and one of the m analog switches connected to the second OTA, capacitors having desired capacitance are selected from the capacitors constituting a filter section. As a result, the adjustment range of the cut-off frequency by the automatic cut-off frequency adjustment circuit can be expanded.

Abstract: The invention relates to an elementary biquadratic cell for programmable time-continuous analog filters. The biquadratic cell is coupled between a first voltage reference and a second voltage reference and has at least one pair of input terminals and first and second pairs of output terminals. The cell includes a pair of half-cells, which half-cells are structurally identical with each other. Each half-cell comprises at least a first transistor coupled between the first and the second voltage reference and having a base terminal connected to a respective one of the input terminals. Each half-cell further comprises second and third transistors coupled between the first and second voltage references. The second transistor has a base terminal connected to the first output terminal of the first pair of output terminals and a collector terminal connected to the first output terminal of the second pair of output terminals.

Abstract: A transistor device having a plurality of transistor cells. Each one of the cells has a control electrode for controlling a flow of carriers through a semiconductor. The device has an input node. A plurality of filters is provided. Each one of the filters is coupled between the input node and a corresponding one of the control electrodes of the plurality of transistor cells. In one embodiment of the invention, pairs of the control electrodes are connected to a common region and wherein each one of the filters is coupled between the input node and a corresponding one of the common regions. The semiconductor provides a common active region for the plurality of transistor cells.

Abstract: Power amplifiers having reactive networks (such as classes C, C-E, E and F) employ tunable reactive devices in their reactive networks, with the reactive devices respective reactance values capable of being adjusted by means of respective control signals. The tunable reactive devices are made from micro-electromechanical (MEM) devices capable of being integrated with the control circuitry needed to produce the control signals and other amplifier components on a common substrate. The reactive components have high Q values across their adjustment range, enabling the amplifier to produce an output with a low harmonic content over a wide range of input signal frequencies, and a frequency agile, high quality output. The invention can be realized on a number of foundry technologies.

Abstract: A semiconductor device of the type having an integrated circuit with connection terminals connected to metal pads by connecting wires is provided. The integrated circuit includes a semiconductor substrate having a lower portion on top of which there is an upper layer that is more heavily doped than the lower portion. A first block and a second block are produced in the upper part of the substrate, and decoupling means are arranged in the vicinity of the first block. The decoupling means include at least one decoupling circuit that is connected to the lower portion of the substrate and to a ground connection pad, and the decoupling circuit has a minimum impedance at a predetermined frequency. In one preferred embodiment, the decoupling circuit includes an inductive-capacitive resonant circuit having a resonant frequency substantially equal to the predetermined frequency.

Abstract: A filter circuit includes two current amplifiers and two capacitors constituted of MOS or MIS transistors. An output terminal of the first current amplifier is connected to an input terminal of the second current amplifier, while an output terminal of the second current amplifier is connected to an input terminal of the first current amplifier. One end of the first capacitor is connected to the input terminal of the first current amplifier, while one end of the second capacitor is connected to the output terminal of the first current amplifier the other end thereof is grounded. When an input signal is supplied through the first capacitor, an output signal through a band-pass filter is issued from the output terminal of the first current amplifier, and an output signal through a high-pass filter is issued from the output terminal of the second current amplifier.

Abstract: Provided is a circuit arrangement for attaining an all-pass filter characteristics which have been conventionally attained by bipolar transistors, by using MIS transistors. An alternating-current signal is input to an input terminal of an inversion circuit having a two-fold amplification function through a low-pass filter. When output from the inversion circuit is input to a gate of a lower transistor of two MIS transistors cascaded and an inverted signal of the alternating-current signal is input to a gate of an upper transistor of the two MIS transistors cascaded, the alternating-current signal is subtracted from the output from the inversion circuit. In this manner, the all-pass filter is formed.

Abstract: A feedback circuit is connected between the input electrode of amplifying element of an amplifying circuit of the initial stage and the output electrode of amplifying element of an amplifying circuit of the final stage. The feedback circuit is structured by a serial circuit of a voltage dropping means resulting in almost constant voltage drop regardless of an increase or decrease of current and a feedback resistor, and a bias voltage is supplied, via the feedback circuit, to an input electrode of the amplifying element in the amplifying circuit of the initial stage from an output electrode of the amplifying element in the amplifying circuit of the final stage. Thereby, current dissipation is reduced and signal loss is lowered.

Abstract: A transconductance filter control system for compensating for drift in transconductance of a slave transconductance amplifier in a continuous time transconductance filter including: a master transconductance amplifier having an output which is a function of its transconductance and a control input for controlling the transconductance of the master transconductance amplifier; a tuning signal source for providing a tuning signal representative of a preselected characteristic of the transconductance filter; a comparing circuit, responsive to any deviation from a predetermined difference between the tuning signal and the output of the master transconductance amplifier, representative of a deviation of the transconductance of the master transconductance amplifier, for providing a compensation signal; and a circuit for applying the compensation signal to the control input of the master transconductance amplifier and to the control input of the slave transconductance amplifier in the transconductance filter to adjus

Abstract: There is disclosed a low frequency filter. A low frequency cutoff filter includes a filter circuit having a capacitor connected between an input terminal and an output terminal and an active resistor connected to the output terminal, having a very large resistance, and a bias circuit having a negative feedback to set a biasing voltage of the active resistor to a desired value, thereby implementing the cutoff filter within a semiconductor chip as one set with the capacitor having a small capacitance. A low frequency pass filter includes an active resistor having a very large resistance, means for setting a biasing voltage of the active resistor to a desired value, and a capacitor connected between the output terminal and the ground. Therefore, the low pass filter can be integrated-circuited using even small capacitor.

Abstract: In this filter circuit, the emitter of a transistor Q1 is connected to the collector of a transistor Q2, and the base of the transistor Q2 is connected to the emitter of a transistor Q3 and the collector of a transistor Q4. The base of the transistor Q4 is connected to the collector of the transistor Q2. A capacitor C1 is connected between the emitters of the transistors Q2 and Q4, and a capacitor C2 is connected between the collectors of the transistors Q2 and Q4. With this arrangement, the filter circuit consumes a small power, is hardly influenced by the parasitic capacitance, can operate at high frequencies, and has a wide dynamic range.

Abstract: A circuit and method for lowering the corner frequency of a differential preamplifier having an AC coupling circuit includes a compensation circuit to adjust the frequency response characteristics created by the AC coupling circuit. An RC network in the compensation circuit is configured to provide a canceling zero at the corner frequency of the AC coupling circuit. The RC network also provides a pole at a desired frequency lower than the corner frequency of the AC coupling circuit, in order to define the overall preamplifier corner frequency. The compensation circuit allows the capacitance in the AC coupling circuit to be significantly reduced, eliminating the need for external components or a very large integrated capacitance.

Abstract: A variable transconductance method and circuit is disclosed along with a filter and an amplifier using the same. An output transconductance is set by selectively adding at least two transconductances which are set according to a select signal for variably selecting an output transconductance.

Abstract: A tunable balanced RC filter circuit of the type in which the resistors are formed as MOS transistors with variable gate voltages for tuning the filter. The MOS transistor takes the form of a series arrangement of individual MOS transistors (T1-1, T1-2, . . . , T1-N; T2-1, T2-2, . . . , T2-N) each having the same d.c. bias on its gate. The gate of each of the individual MOS transistors in the series arrangement also receives a fraction of the a.c. component of the input signal on the input terminals (IT1, IT2) of the two-port network by means of a resistor ladder (R1-1, R1-2, . . . , R1-N, R2-1, R2-2, . . . , R2-N), which is connected to the input terminals (IT1, IT2) via buffers (B1, B2). The a.c. component of the input signal is thus divided among the individual transistors in the series arrangement. In this way it is possible to use MOS transistors with a small gate voltage swing at comparatively large input voltages.

Abstract: A second-order differential highpass filter constructed according to the present invention includes a difference amplifier and a feedback processing circuit. The difference amplifier includes an operational amplifier OP.sub.1, and four resistors R.sub.3, R.sub.4, R.sub.5 and R.sub.6, wherein R.sub.4 /R.sub.3 =R.sub.6 /R.sub.5. An input voltage V.sub.1 is fed to the inverting terminal (-) of the operational amplifier OP.sub.1 via the resistor R.sub.5. Another input voltage V.sub.2 is fed to the noninverting terminal (+) of the operational amplifier OP.sub.1 via the resistor R.sub.3. The output of the operational amplifier OP.sub.1 is fed back to the inverting terminal (-) of the operational amplifier OP.sub.1 via the resistor R.sub.6. The feedback processing circuit includes an operational amplifier OP.sub.2, two resistors R.sub.1 and R.sub.2, and two serial capacitors C.sub.2 and C.sub.1. The output of the operational amplifier OP.sub.

Abstract: A compensated, bias-dependent signal filtration and amplification circuit includes a low-pass RC filter with a bias-dependent frequency response caused by the use of MOS transistors connected as capacitors with bias-dependent capacitances. A dc current source is used, in cooperation with the resistors of the RC filter, to generate a fixed bias for the capacitor-connected MOS transistors and thereby eliminate the bias dependencies of the capacitances. Following amplification of the filtered signal, another dc current is subtracted out from the amplified output signal so as to eliminate any residual dc signal components due to the input compensation dc bias signal, thereby leaving only the amplified filtered ac signal components.

Abstract: Active filter circuit 1 consists of five filter stages 70-74 cascoded between a voltage supply and ground potential. The circuit has two major current paths, the first through the collector-emitter paths at transistors 31, 33, 35, 37 and 39, the second through transistors 32, 34, 36, 38 and 40. Each major current path is driven by a current source 61, 62. In operation, a differential input signal is applied to the base electrodes of transistors 31, 32 and a differential output signal is taken from the emitters of transistors 39, 40. The transistors 33, 34 of stage 71 have their collector and base electrodes cross-coupled. Transistors 35-40 of stages 72-74 are connected in the same manner. In another embodiment (FIG. 3, not shown) a cut-off frequency is varied under control of controllable current sources.

Abstract: An apparatus for stabilizing cut-off frequency using a transconductance, especially used in a high-frequency filter circuit, capable of maintaining constant frequency characteristics regardless of noise in association with a clock frequency, changes in the temperature, changes in the power supply voltage and errors in fabrication, when a filter circuit is installed in an IC (Integrated Circuit). The apparatus includes a filtering unit for passing only signals having a frequency band predetermined in the IC; a transconductance setting unit, installed out of the IC, for controlling a transconductance of the filtering unit; and a controlling unit for controlling a transconductance of the transconductance setting unit.

Abstract: The invention relates to a distributed amplifier for wide band hyperfrequency signals of the type comprising:a plurality of basic amplifying cells (C.sub.1 to C.sub.n) mounted in series, with at least one common drain line (Ld) and at least one common grid line (Lg), each cell comprising at least one field effect transistor (T.sub.1) which is common-source mounted and filtering elements,first biasing means for applying a first biasing voltage (Vd) to the common drain line, andsecond biasing means for applying a second biasing voltage to the common grid line. According to the main feature of the invention, the first biasing means comprise a plurality of auxiliary field effect transistors (T'.sub.1 to T'.sub.n) functioning in saturable load mode and whose respective sources (S'.sub.1 to S'.sub.n) are distributively connected up to the common drain line (Ld) and whose respective drains (D'.sub.1 to D'.sub.n) receive in series the first biasing voltage (Vd).

Abstract: A description is given of a circuit arrangement comprisinga filter quadripole having two output terminals anda voltage follower circuit having two terminals, said terminals having identical electric potentials when the voltage follower circuit is in its turned-on state, each of the terminals of the voltage follower circuit being connected to one of the output terminals of the filter quadripole respectively, and the voltage follower circuit only being in its turned-on state during the turn-on time interval of the circuit arrangement. This circuit arrangement is suitable for a receiver circuit, more particularly, for a pager and has a very brief turn-on time.

Abstract: A filter circuit comprises three stages 260, 270, 280, each having a differential input and a differential output. The output of stage 260 serves as the input of stage 270 and the output of stage 270 serves as the input of stage 280 respectively. Stage 260 comprises two transistor pairs 201, 202 and 203, 204. An input signal is applied to the base electrodes of transistors 201, 204 which causes a current change in their opposite transistor 202, 203. Transistors 202, 203 have their respective base and collector electrodes connected together. The collector electrodes of transistors 202, 203 constitute the output of stage 260. Stages 270 and 280 have essentially the same structure as stage 260. The arrangement offers high frequency capabilities from a low supply voltage. In another embodiment, a cut-off frequency is varied under control of controllable current sources.

Abstract: A differential attenuator is described that is capable of automatic calibration using electronically adjustable circuit elements. The differential attenuator has positive and negative inputs and outputs. A resistor and capacitor couple the positive side input and output, while a matching resistor and capacitor couple the negative side input and output. Shunt resistors and shunt capacitors coupled to the positive and negative outputs are augmented and made electronically adjustable by multipliers having their signal inputs coupled to the respective side output nodes. The outputs of one set of multipliers are coupled to the other ends of the shunt resistors, while their multiplication coefficients are controlled by a dc.sub.-- control signal. The outputs of another set of multipliers are capacitively coupled back to their respective side output nodes, while their multiplication coefficients are controlled by an ac.sub.-- control signal.

Abstract: A filter circuit using junction capacitors of semiconductors of the present invention prevents the distortion of signal waveforms and is not affected by parasitic capacitors. The filter circuit includes a resistor whose first terminal is connected to an input terminal and whose second terminal is connected to an output terminal. A first junction capacitor is connected between a control voltage supply terminal and an output terminal and a second junction capacitor is connected between the output terminal and ground. An alternate embodiment of the filter circuit includes a pnp transistor, whose emitter is connected to the direct current power supply via a resistor, whose collector is grounded, and whose base is connected to the output terminal.