Abstract: An apparatus for detecting a periodic timing reference in a received signal comprises a correlator and an integrator. The correlator is configured to correlate the received signal with a template to produce a correlated signal indicating the presence of the periodic timing reference in the received signal. The integrator is configured to produce an accumulated signal by overlaying one or more delayed versions of the accumulated signal onto the correlated signal, and is further configured to delay the accumulated signals by integer multiples L of a period of the periodic timing reference, the integer multiples L being at least two.

Abstract: The present invention discloses a circuit sharing time delay integrator structure. The major composing elements of this circuit sharing time delay integrator structure are: a sharing circuit, a first control block, a plurality of second control blocks and a timing set generated by a timing generator circuit. The sharing circuit can be an OP-AMP, an active load, or any of a variety of combinations used in signal accumulation applications. With the implementation of the present invention to applications of signal accumulations, the necessity of an adder circuitry is eliminated, the overall circuitry and hence the total amount of transistors required when producing the integrated circuit is massively reduced, and thus a great cost reduction and better timing and power efficiency can all be thereof achieved.

Abstract: Capacitive level-shifting circuits and methods are provided for adding DC offsets to the output of a current-integrating amplifier. For example, a current-integrating amplifier includes an input amplifier stage and an output offset circuit. The input amplifier stage includes an input node, a first output node, and a first switch connected between the first output node and a power supply node. The output offset circuit is connected to the first output node of the input amplifier stage and to a second output node of the current-integrating amplifier. The output offset circuit includes a first series capacitor coupled between the first output node of the input amplifier stage and the second output node of the current-integrating amplifier. The output offset circuit switchably connects a bias voltage to the second output node and charges the first series capacitor to add a DC offset to the second output node of the current-integrating amplifier.

Abstract: A mixed signal correlator utilizes coherent detection within a capacitance measurement application. In some applications, the mixed signal correlator is used to measure capacitance of a touch screen display. An external capacitor whose capacitance is measured is kept small for improved sensitivity and can be used for a variety of applications having varied integration periods for measurement. The external capacitor is kept small and can be used for varied applications by adjusting the output voltage within a range that is less than the supply voltage, and maintaining a count of the adjustments to later reconstruct an actual output voltage for the integration period. An output is a weighted sum of an analog integrator output and a digital counter output.

Abstract: An apparatus comprises an amplifier circuit comprising at least one output node and a common-mode restoration circuit capacitively coupled to the at least one output node of the amplifier circuit. The common-mode restoration circuit is configured to introduce at least one common-mode restoring signal onto the output node, wherein the at least one common-mode restoring signal transitions in correspondence with an operation interval of the amplifier circuit and thereby compensates for a common-mode voltage drop on the at least one output node of the amplifier circuit. In one example, the amplifier circuit may comprise a current-integrating amplifier circuit, and the operation interval may comprise an integration interval.

Abstract: A mixed signal correlator utilizes coherent detection within a capacitance measurement application. In some applications, the mixed signal correlator is used to measure capacitance of a touch screen display. An external capacitor whose capacitance is measured is kept small for improved sensitivity and can be used for a variety of applications having varied integration periods for measurement. The external capacitor is kept small and can be used for varied applications by adjusting the output voltage within a range that is less than the supply voltage, and maintaining a count of the adjustments to later reconstruct an actual output voltage for the integration period. An output is a weighted sum of an analog integrator output and a digital counter output.

Abstract: An integrator circuit with multiple time window functions for carrying out a plurality of integration operations in parallel, each integration operation being carried out in a coherent manner over a sequence of time windows including at least one such window. The circuit includes a plurality of integration paths each corresponding to an integration operation. The integration paths share a same voltage/current converter and a same first switching mechanism for switching a signal to be integrated at an input of the converter, each integration path further including at least one integration capacitor mounted in counter-reaction to a functional amplifier and receiving a resulting current via a second switching mechanism for selecting the path.

Abstract: A circuit includes a first amplifier and a second amplifier, wherein first amplifier is configured to receive an input current at a first input of the first amplifier, and an output of the first op-mp is configured to drive a first input of the second amplifier. The circuit further includes a pull-up current source selectively coupled to the first input of the second amplifier, and a pull-down current source selectively coupled to the first input of the second amplifier. If the absolute value of the input current is larger than a predefined threshold current: i) the pull-up current source is configured to drive current into the first input of the second amplifier for a first polarity of the input current, and ii) the pull-down current source is configured to sink current from the first input of the second amplifier for a second polarity of the input current.

Abstract: A capacitance to frequency converter includes a switching capacitor circuit, a charge dissipation circuit, a comparator, and a signal generator. The switching capacitor circuit charges a sensing capacitor and transfers charge from the sensing capacitor to a circuit node of the charge dissipation circuit. The comparator is coupled to the charge dissipation circuit to compare a potential at the circuit node to a reference voltage. The signal generator is coupled to an output of the comparator and to the charge dissipation circuit. The signal generator is responsive to the output of the comparator to generate a signal fed back to control the charge dissipation circuit. A frequency of the signal is proportional to a capacitance of the sensing capacitor.

Abstract: Embodiments of the invention are generally directed to a high-speed differential energy difference integrator (EDI) for adaptive equalizers. In an embodiment, the EDI includes two differential full-wave rectifiers providing differential outputs that are cross-coupled to the inputs of an integration capacitor. In one embodiment, the active areas of the transistors of the differential full-wave rectifiers are substantially the same.

Abstract: A technique includes charging and discharging a capacitive sensor of a display. The technique includes regulating currents that are associated with the charging and discharging based at least in part on a reference time interval and determining a capacitance sensed by the capacitive sensor based at least in part on the regulating.

Abstract: In control of the disk array device (backup system), when a blackout occurs, the disk array device is first operated in a first method to backed up a main memory by using a power supply from a battery. During the first method, a blackout continuous time and the like are integrated, and at a timing in which the integrated value satisfies a condition, the first method is then shifted to the second method to evacuate data from the main memory onto a nonvolatile memory based on a power supply.

Abstract: A switched charge storage element integrator in a continuous or discrete time circuit, the integrator including a differential input amplifier, a first 2-terminal charge storage element, a second 2-terminal charge storage element, and a plurality of controlled switches. The differential input amplifier is coupled to a capacitor and a resistor and configured as an inverting integrator. An inverting terminal of the amplifier is coupled to two controlled switches. A non-inverting terminal of the amplifier is coupled to a reference voltage. The first and second switched charge storage element blocks are alternatingly coupled to the inverting terminal INM of the amplifier XOPA during the active state of a second clock signal and a first clock signal, respectively, for making the supply noise continuous and eliminating its dependency on the clock phases, thereby zeroing its convolution with the clock signal.

Abstract: An active RC resonator includes a first operational amplifier having first and second inputs and first and second outputs, a second operational amplifier having first and second inputs and first and second outputs, a first resistor coupled between the first input of the first operational amplifier and the second output of the second operational amplifier, a second resistor coupled between the second input of the first operational amplifier and the first output of the second operational amplifier, a third resistor coupled between the first output of the first operational amplifier and the first input of the second input of the second operational amplifier, a fourth resistor coupled between the second output of the first operational amplifier and the second input of the second operational amplifier, and at least one of 1) a first capacitor coupled between the first input of the first operational amplifier and the first output of the second operational amplifier, and a second capacitor coupled between the second

Abstract: Device for determining an error induced by a high-pass filter in a signal, including a unit (3) for calculating the error according to the formula: E(t)=Ve(t)?Vs(t)=2·?·Fc·??=t0t(Vs(?)? Vs(?))·d?+E(t0) with: E(t) the value of the error induced by the high-pass filter, as a function of the time variable t, ?the trigonometric constant, Fc the cutoff frequency of the high-pass filter, t0 the initial instant, ?integration variable, Ve the signal input to the high-pass filter, Vs the signal output by the high-pass filter, Vs the mean value of the signal Vs. A method of correcting the error induced is also presented and applicable to the error correction of a piezoelectric pressure sensor.

Abstract: A delta-sigma modulator is disclosed which has a filter comprising a filter input, two LC resonators (LC1-1, LC1-2), and two switches (CBT/CGT). An input of each one of the two switches is connected to the filter input and a corresponding output of each one of the two switches is connected to a corresponding one of said LC resonators. Each one of the two switches is individually controllable for selectively connecting the corresponding one of the LC resonators with the filter input. The invention also relates to a method for changing the mode of operation of a delta-sigma modulator.

Abstract: An integrated circuit integrator includes a first transconductance amplifier having a gain adjustable based upon a first control signal, and receives, as an input, a signal to be filtered, and generates, as an output, a corresponding amplified signal. The first transconductance amplifier includes an R-C output circuit to filter components from the amplified signal, and an output resistance being adjustable based upon a second control signal. A second transconductance amplifier is matched with the first transconductance amplifier, and has a gain adjustable based upon the first control signal, and a matched output resistance adjustable based upon the second control signal. A circuit is configured to force a reference current through the matched output resistance. An error correction circuit is coupled to the second transconductance amplifier and is configured to generate the second control signal so as to keep constant a voltage on an output of the second transconductance amplifier.

Abstract: Systems and methods are provided for power measurement of signals such that the power measurement is insensitive to PVT variations of the measurement systems. A power measurement system includes an analog squarer circuitry, an integrating ADC, and a controller. The squarer circuitry calculates the power of a signal whose power is to be measured while the integrating ADC integrates the calculated power over a runup interval to generate an integrated power. The squarer circuitry also calculates the power of a reference for the integrating ADC to de-integrate the integrated power over a rundown interval. The power measurements are independent of PVT variations of the analog squarer circuitry and integrating ADC. The controller digitally controls the runup interval and measures the rundown interval to provide digitized power measurements. The analog squarer circuitry have replica squarer circuits. Process dependent mismatches between the replica analog circuitry may be removed through a calibration process.

Abstract: A receiver includes: an amplifier that amplifies a received broadband signal up to a predetermined level; a first switch that switches an output signal from the amplifier; a signal generator that generates a signal for controlling a switching operation of the first switch; an integration capacitor that integrates an output signal from the first switch; a comparator that compares an output voltage from the integration capacitor with a predetermined voltage; and a reset circuit that discharges electrical charges accumulated in the integration capacitor based on a comparison result from the comparator.

Abstract: Broadband analog radio-frequency devices can be used to create building blocks for scalable analog signal processors that operate over bandwidths of 50 MHz to 20 GHz or more. Example devices include integrators (transconductors), digitally controlled attenuators, buffers, and scalable summers implemented using deep sub-micron CMOS technology. Because the devices are implemented in CMOS, the ratio of trace/component size to signal wavelength is about the same as that of low-frequency devices implemented in printed circuit boards. Combining this scaling with high gain/high bandwidth enables implementation of feedback and programmability for broadband analog signal processing.

Abstract: Embodiments of the invention are generally directed to a high-speed differential energy difference integrator (EDI) for adaptive equalizers. In an embodiment, the EDI includes two differential full-wave rectifiers providing differential outputs that are cross-coupled to the inputs of an integration capacitor. In one embodiment, the active areas of the transistors of the differential full-wave rectifiers are substantially the same.

Abstract: An active integrator for sensing capacitance of a touch sense array is disclosed. The active integrator is configured to receive from the touch sense array a response signal having a positive portion and a negative portion. The response signal is representative of a presence or an absence of a conductive object on the touch sense array. The active integrator is configured to continuously integrate the response signal.

Abstract: An integrated circuit integrator includes a first transconductance amplifier having a gain adjustable based upon a first control signal, and receives, as an input, a signal to be filtered, and generates, as an output, a corresponding amplified signal. The first transconductance amplifier includes an R-C output circuit to filter components from the amplified signal, and an output resistance being adjustable based upon a second control signal. A second transconductance amplifier is matched with the first transconductance amplifier, and has a gain adjustable based upon the first control signal, and a matched output resistance adjustable based upon the second control signal. A circuit is configured to force a reference current through the matched output resistance. An error correction circuit is coupled to the second transconductance amplifier and is configured to generate the second control signal so as to keep constant a voltage on an output of the second transconductance amplifier.

Abstract: A mixed-signal integrator, having an analog input and a digital output, is adapted to perform an integration operation partially in the analog domain and partially in the digital domain while eliminating the limitations of a conventional analog integrator. The integrator also digitizes a signal of interest without the use of a conventional sampling operation followed by a conventional analog-to-digital converter. The analog integrator portion generates an analog integration signal limited between low and high rail voltages defined by two comparators with corresponding threshold voltages. When either rail voltage is reached, the polarity of the input signal is reversed to prevent the integration result from exceeding that rail. Each such event is also tracked in digital logic, which provides a count whenever two consecutive such events correspond to the two different rails. At the end of the integration duration this count serves as the digital representation of the integration result.

Abstract: A high order integrator is configured using an operational amplifier, a first filter connected between an input terminal of the integrator and an inverted input terminal of the operational amplifier, and a second filter connected between the inverted input terminal and output terminal of the operational amplifier. The first filter includes n serially-connected first resistance elements, n-1 first capacitance elements each connected between each interconnecting node of the first resistance elements and the ground, and n-1 second resistance elements each connected between each interconnecting node of the first resistance elements and the ground. The second filter includes n serially-connected second capacitance elements, n-1 third resistance elements each connected between each interconnecting node of the second capacitance elements and the ground, and n-1 third capacitance elements each connected between each interconnecting node of the second capacitance elements and the ground.

Abstract: An oversampling A/D converter with a few operational amplifiers is configured using a complex second-order integrator including first and second second-order integrators and first and second coupling circuits configured to couple these integrators together. Each of the second-order integrators includes an operational amplifier, four resistance elements, and three capacitance elements. The first coupling circuit cross-couples one of two serially-connected capacitance elements inserted between the inverted input terminal and output terminal of the operational amplifier in the first second-order integrator to the counterpart in the second second-order integrator using two resistance elements. The second coupling circuit cross-couples the other capacitance element in the first second-order integrator to the counterpart in the second second-order integrator using two resistance elements.

Abstract: An integrated circuit device includes a sense amplifier with an input to receive a present signal representing a present bit. The sense amplifier is to produce a decision regarding a logic level of the present bit. The integrated circuit device also includes a circuit to precharge the input of the sense amplifier by applying to the input of the sense amplifier a portion of a previous signal representing a previous bit. The integrated circuit device further includes a latch, coupled to the sense amplifier, to output the logic level.

Abstract: A circuit includes a first amplifier and a second amplifier, wherein first amplifier is configured to receive an input current at a first input of the first amplifier, and an output of the first op-mp is configured to drive a first input of the second amplifier. The circuit further includes a pull-up current source selectively coupled to the first input of the second amplifier, and a pull-down current source selectively coupled to the first input of the second amplifier. If the absolute value of the input current is larger than a predefined threshold current: i) the pull-up current source is configured to drive current into the first input of the second amplifier for a first polarity of the input current, and ii) the pull-down current source is configured to sink current from the first input of the second amplifier for a second polarity of the input current.

Abstract: A method according to one embodiment includes receiving an increment signal at a first integrator when a second integrator overflows; receiving a decrement signal at the first integrator when the second integrator underflows; and incrementing or decrementing a gain applied to an analog signal based on receipt of the increment or decrement signal. A system according to one embodiment includes a first integrator configured to cause incrementing of a gain applied to an analog signal based on receipt of an increment signal when a second integrator overflows, the first integrator being configured to cause decrementing of the gain applied to the analog signal based on receipt of a decrement signal when the second integrator underflows; and the second integrator.

Abstract: An arrangement for charge integration comprises an input (1) for the provision of a charge-dependent signal and an integrator (30) to integrate a signal present at its input. In addition, a coupling circuit (20) that can adopt at least two operating states is provided to couple the input (1) to the integrator (30) which has a temperature-dependent coupling characteristic. A correction circuit (10) that can be operated by a clock signal is coupled to the input (1) in order to transfer a quantity of charge, and has a temperature characteristic that is derived from the coupling characteristic of the coupling circuit (20).

Abstract: A capacitance to frequency converter includes a switching capacitor circuit, a charge dissipation circuit, a comparator, and a signal generator. The switching capacitor circuit charges a sensing capacitor and transfers charge from the sensing capacitor to a circuit node of the charge dissipation circuit. The comparator is coupled to the charge dissipation circuit to compare a potential at the circuit node to a reference voltage. The signal generator is coupled to an output of the comparator and to the charge dissipation circuit. The signal generator is responsive to the output of the comparator to generate a signal fed back to control the charge dissipation circuit. A frequency of the signal is proportional to a capacitance of the sensing capacitor.

Abstract: A switched-capacitor decimator that can attenuate undesired signal components at odd harmonics of an output sample rate is described. In one design, the switched-capacitor decimator includes at least one sampling capacitor and multiple switches. For each sampling capacitor, the top plate is charged with a first input signal when the capacitor is selected for top charging, and the bottom plate is charged with a second input signal when the capacitor is selected for bottom charging. For each sampling capacitor, the top plate provides its stored charges to a first output signal and the bottom plate provides its stored charges to a second output signal when the capacitor is selected for reading. The switches couple the at least one sampling capacitor to the first and second input signals for charging and to the first and second output signals for reading.

Abstract: A read circuit includes: an integration circuit section configured to perform an integral operation and whose input is connected to an integration node; and a bias circuit connected between a connection node to which a variable resistive element is connected and the integration node. The bias circuit includes: an integration transistor whose source and drain are respectively connected to the connection node and the integration node; an operational amplifier whose output is connected to a gate of the integration transistor, to whose first input a bias voltage is supplied, and whose second input is connected to the source of the integration transistor; and at least one diode element that is connected between the gate and source of the integration transistor and clips a gate-source voltage of the integration transistor.

Abstract: A sensing device able to do concurrent real time detection of different kinds of chemical, biomolecule agents, or biological cells and their respective concentrations using optical principles. The sensing system can be produced at a low cost (below$1.00) and in a small size (˜1 cm3). The novel sensing system may be of great value to many industries, for example, medical, forensics, and military. The fundamental principles of this novel invention may be implemented in many variations and combinations of techniques.

Abstract: Systems and methods for maintaining a drive signal to a resonant circuit at a resonant frequency are provided. A system for maintaining a drive signal to a resonant circuit at a resonant frequency can include: an oscillator configured to provide an output to a phase comparator and a drive circuit, the drive circuit configured to provide a drive signal to a resonant circuit; a phase detector configured to receive a filtered version of the drive signal from the resonant circuit and provide a phase-indicating signal to the phase comparator; and the phase comparator, wherein the phase comparator is configured to provide a signal based on the phase difference between the oscillator output and the phase-indicating signal, wherein the signal from the phase comparator is used to control the frequency of the oscillator such that the phase difference converges to a fixed value.

Abstract: A multi-channel integrator is provided. The multi-channel integrator includes an integrator and a plurality of channels. Each of the channels includes an input selector and a unit-gain amplifier. The input selector has a common terminal, a first selecting terminal and a second selecting terminal. The input selector selectively electrically connects the common terminal to the first selecting terminal or to the second selecting terminal. The first selecting terminal of the input selector is coupled to an input terminal of the integrator. An input terminal of the unit-gain amplifier is coupled to the second selecting terminal of the input selector.

Abstract: An equalizer circuit includes: a plurality of amplifiers that convert a voltage signal into a current; a plurality of capacitive loads that are charged and discharged in accordance with respective outputs of the plurality of amplifiers; a charge discharge circuit provided for each of the plurality of capacitive loads to charge or discharge one of the plurality of capacitive loads; and a reset circuit provided for each of the capacitive loads to initialize the charge stored in the one of the plurality of capacitive loads, wherein a current according to the voltage signal is integrated in different periods for each of the plurality of capacitive loads and the capacitive load is discharged through the current in a first period and the capacitive load is charged through the current in a second period following the first period.

Abstract: An integrator includes an operational amplifier, a first filter connected to an inverting input terminal of the operational amplifier, and a second filter connected between the inverting input terminal and an output terminal of the operational amplifier. The first filter includes n resistive elements connected in series, and (n?1) capacitive elements each having one end connected to an interconnecting node of the resistive elements and the other end connected to ground. The second filter includes n capacitive elements connected in series, and (n?1) resistive elements each having one end connected to an interconnecting node of the capacitive elements and the other end connected to ground.

Abstract: A multi-channel integrator includes a first switch, a second switch, and a plurality of integration units. First terminals of the first and second switches receive a first reference voltage. Each of the integration units includes an operational amplifier (OP-AMP), a feedback switch, a third switch, a fourth switch, and a feedback capacitor. A second input terminal of the OP-AMP receives a second reference voltage. Two terminals of the feedback switch are respectively coupled to a first input terminal and an output terminal of the OP-AMP. First terminals of the third switch and the fourth switch are respectively coupled to the first input terminal and the output terminal of the OP-AMP. A first terminal of the feedback capacitor is coupled to the second terminals of the first and the third switches. A second terminal of the feedback capacitor is coupled to the second terminals of the second and the fourth switches.

Abstract: A sampling filter device wherein the filter characteristic is variable without using a control signal of a complicated waveform is provided. A sampling filter device 105 has integration capacitors 130 and 131, an integration time adjustment section 180, and a plurality of switches 100, 101, 110, and 111. Input current is integrated in different time duration with one clock and is stored in the integration capacitors 130 and 131 and charges stored in the integration capacitor from several clocks before to one clock before are added and the result is output. When charge is stored in the integration capacitors 130 and 131 with each clock, the integration time duration is changed, whereby it is made possible to weight and add output charge and the filter characteristic changes.

Abstract: The invention relates to a pulse width modulator, more particularly to a cross-coupled pulse width modulator. A crossing input signal modulator according to the present invention comprises: a positive path block which includes a first integrator for performing the first-order integration of feedback signals in first input and output signals and then transmitting the first—order integrated signals to a second integrator, and a second integrator for performing the second-order integration of a signal from the first integrator and a second input signal and then transmitting the second-order integrated signals; and a negative path block which includes a third integrator for performing the first-order integration of feedback signals in the second input and output signals and integration of a signal from the third integrator and the first input signal and then transmitting the second-order integrated signals.

Abstract: It is possible to provide a voltage-current converter which can realize a variable filter having a steep cut-off characteristic with a small area. The voltage-current converter includes: one or more sampling/holding units for sampling an inputted voltage and holding the sampled voltage; one or more separate voltage-current conversion units for outputting a current corresponding to the voltage held by the sampling/holding units; and a control unit for controlling the timing of the sampling and holding of the inputted voltage by the sampling/holding units.

Abstract: An integrating amplifier on an IC, which comprises a feedback loop using an external device as an integrating capacitor, has added a second feedback loop that provides an additional current to the input of the amplifier, which current can be used to increase the input range of the charge that can be measured without needing another external capacitor or pad.

Abstract: A multiphase receiver to compensate for intersymbol interference in the sampling of an input signal includes a first integrating receiver to integrate and sample data of the input signal on a first phase of a clock and a second integrating receiver to integrate and sample data of the input signal on a second phase of the clock. The multiphase receiver also includes an equalization circuit to adjust integration by the first integrating receiver dependent on a result of integration of data previously received by an integrating receiver distinct from the first integrating receiver, and to adjust integration by the second integrating receiver dependent on a result of integration of data previously received by an integrating receiver distinct from the second integrating receiver.

Abstract: A system according to one embodiment includes an analog input for receiving an analog signal; a variable gain amplifier coupled to the analog input; a first integrator coupled to the variable gain amplifier for controlling the gain of the analog signal; a second integrator generating control signals for controlling functions of the first integrator; a serializer for serializing the control signals; and a deserializer coupled to the serializer for deserializing the control signals and passing the deserialized control signals to the first integrator.

Abstract: An arrangement for charge integration comprises a charge-generating circuit (2) that provides a charge-dependent signal, and a coupling circuit (20) comprising a first and a second transistor (T1, T2). The first transistor (T1) can be controlled in dependence on the charge-dependent signal. The second transistor (T2) is configured to forward the charge-dependent signal in dependence on a control signal provided by the first transistor (T1). The forwarded charge-dependent signal is integrated by an integrator (30).

Abstract: A fail-safe differential receiver having a differential amplifier adapted to receive first and second differential input signals and generate a differential voltage. A peak detector is coupled to the differential amplifier for generating a detect signal and a comparator is coupled to the peak detector for comparing the detect signal to a threshold voltage and providing a comparison signal. A directing circuit is coupled to the differential amplifier for receiving the first and second differential input signals and is coupled to the comparator for receiving the comparison signal. An output amplifier is coupled to the directing circuit. The directing circuit selectively directs the first and second differential input signals to the output amplifier as a function of the value of the comparison signal from the comparator.

Abstract: An integrating amplifier on an IC, which comprises a feedback loop using an external device as an integrating capacitor, has added a second feedback loop that provides an additional current to the input of the amplifier, which current can be used to increase the input range of the charge that can be measured without needing another external capacitor or pad.

Abstract: In a method and system for filtering an input signal with a filter included in a phase locked loop (PLL), a unidirectional feedback path is configured from an output of the filter to an input of the filter. The unidirectional feedback path includes a feedback resistor that is configured to adjust a bandwidth of the PLL. A zero path is configured from the output to a voltage reference, such as ground. The zero path includes a capacitor coupled in series with a bias resistor. The bias resistor, which along with the capacitor determines a zero frequency of the filter, is configured to reduce a value of the capacitor without a substantial increase in a phase noise of the PLL due to the unidirectional nature of the feedback. A reduction in the value of the capacitor enables a corresponding reduction in a silicon area to form the capacitor.

Abstract: Integrated circuitry for selectively introducing capacitance and for controlling the transconductance transfer function of one or more amplifiers includes concatenated differential amplifiers with one or more pairs of switchable capacitive components differentially connected across outputs of the differential amplifiers to facilitate operation over a wide range of operating frequencies under control of external signals.