Abstract: An oscillator circuit having an expanded operating range includes an amplifier portion amplifying an oscillating signal. A gain controlling portion controls the gain of the amplified oscillating signal. A switching circuit electrically connected across the gain controlling portion provides a low impedance electrical path in parallel with the gain controlling portion in response to a switch input signal. The switching circuit further includes a switch signal generator portion producing the switch input signal to switch the switching circuit ON or OFF when power supplied to the oscillator circuit reaches a first predetermined voltage level and to switch the switching circuit OFF or ON when power supplied to the oscillator circuit reaches a second predetermined voltage level. In this circuit design, the initiation of an oscillating signal by the oscillator circuit is unaffected by supply voltage variation or, in other words, fluctuation in the power supplied to the oscillator circuit.

Abstract: Periodically, sensed amplitude for the output signal of a voltage-controlled oscillator is compared to a reference and biasing of the voltage-controlled oscillator is correspondingly set, thereby controlling amplitude of the voltage-controlled oscillator output signal. Process and temperature dependencies of the amplitude are eliminated while achieving low phase noise and large signal-to-noise ratio in the output signal, and consequently low phase noise.

Abstract: Briefly, in accordance with embodiments of the invention, switched capacitors may be utilized to emulate resistors in a longer time constant feedback network for amplitude regulation of a crystal oscillator.

Abstract: A differential varactor is physically defined in a CMOS process using a using the diffusion mask of a polycide gate rather than a P (+) mask, as is commonly used. The differential CMOS varactor may be used in a phase locked loop (PLL) of a voltage-controlled oscillator (VCO) to enable a transceiver to communicate at OC-3/STM-1 data rates using SONET/SDH signaling formats.

Abstract: An amplitude control device for a signal output by an oscillator includes a rectification circuit for rectifying the output signal, and a differential amplification circuit for generating a biasing current control signal for the oscillator. The biasing current control signal is based upon the output signal from the rectification circuit and a reference voltage. A dividing bridge and an adder are designed so that only a fraction of the reference voltage is used to define the amplitude of the oscillations. The contribution made to the oscillator phase noise by the reference voltage noise is considerably reduced.

Abstract: A level detector (110, 104) and corresponding method detects (602) whether an output signal level of a VCO (102) is within a window bounded by minimum and maximum thresholds. When the output signal level is not within the window, a loop-control element (108) closes (604) an AGC loop of the VCO and controls the gain of the VCO with a gain-control signal that tracks an AGC bias signal. When the output signal level is within the window, the loop-control element opens (606) the AGC loop and controls the gain with a fixed bias signal derived from the AGC bias signal at the time the AGC loop is opened.

Abstract: An oscillator circuit is specified, having an LC resonator, to which two or more current paths are connected, which are connected in parallel with one another and can be connected and disconnected individually by switches. The attenuation compensation amplifiers are in this case coupled to the resonant circuit in order to compensate for its attenuation. The oscillator circuit allows the gradient of the compensation for the attenuation of the resonant circuit to be adjusted, without moving the operating point of the amplifiers. This makes it possible to compensate for manufacturing-dependent component tolerances and any amplitude discrepancy caused by them, in a simple way. The oscillator circuit is suitable, for example, for use in voltage-controlled oscillators in order to form phase-locked loops when using mass production technologies.

Abstract: The ignition of a gas discharge lamp is followed by a warm-up phase. During warm-up, sufficient power must be converted to enable the lamp to transition to an operating phase. This causes currents flowing at a damaging level into the electrodes in known devices. These high currents are avoided using: a regulation device that regulates the power of connected gas discharge lamps to a desired power; a setting device that limits a lamp current of connected gas discharge lamps to a limit value; a detection device that outputs a signal to the control device if a limit value setting is too low, putting a connected lamp into a state in which the lamp assumes the desired power; and a control device prescribing the limit value for the setting device and increasing the limit value if the detection device sends a signal to the control device.

Abstract: A rectifier (306) rectifies (402) an output signal of a VCO (302) to produce an envelope signal proportional to an amplitude of the output signal. An integrator (308) integrates (404) the envelope signal to produce a comparison signal, such that, in response to a change in the envelope signal, during a first mode of operation of the VCO, the comparison signal is allowed to change at a first rate, and, during a second mode of operation of the VCO, the comparison signal is allowed to change at a second rate different from the first rate. A comparator (310) compares (406) the comparison signal with a reference signal (316) to produce a bias signal, and controls (408) a gain of the VCO with the bias signal.

Abstract: A circuit controls an oscillation amplitude of a crystal oscillator including a crystal resonator, a current source supplying a bias current, and an output transistor coupled to the crystal resonator and the current source. The circuit includes a peak detector for detecting a peak voltage of an output signal of the crystal oscillator, and a controller coupled to the peak detector and to the current source for controlling the current source in accordance with a difference between the peak voltage and a target voltage, the target voltage being set to be substantially equal to 2Vth, where Vth is a threshold voltage of the output transistor. A frequency control circuit controls a first switched-capacitor array and a second switched-capacitor array coupled to the crystal resonator, and alternately switches a unit capacitor in the first switched-capacitor array and a unit capacitor in the second switched-capacitor array based on a frequency control signal.

Abstract: A highly stable single chip resonator controlled oscillator with automatic gain control designed for manufacture in monolithic integrated circuit technologies. An automatic gain controller monitors the output of a crystal controlled oscillator amplifier and produces a feedback signal to ensure oscillation is induced at startup and that the amplitude of oscillation is continuously controlled during operation to reach low phase noise and reduce power consumption of the circuit.

Abstract: A crystal oscillation circuit using a crystal oscillator comprises an inverting amplifier, a buffer, and a voltage shift circuit. The voltage shift circuit operates in such a way that within prescribed limits by which the output of the inverting amplifier satisfies excitation conditions of the crystal oscillator and by which the oscillation output of the buffer satisfies input conditions of a following circuit, a supply voltage (Vdd) is reduced by a gate threshold voltage of an n-channel MOS transistor, and a ground potential (GND) is increased by a gate threshold voltage of a p-channel MOS transistor with respect to both the inverting amplifier and the buffer. Thus, it is possible to prevent the crystal oscillator from being damaged while suppressing the excitation level of the crystal oscillator even though the gain of the inverting amplifier is increased to be relatively high.

Abstract: A novel circuit topology which provides for the digital automatic gain control of a VCO is disclosed. The topology of the VCO is based on the negative transconductance oscillator due to its intrinsically simple biasing scheme. A system parameter sensitive to the performance level of the VCO is firstly measured. A digital control signal is then generated in response to the measured system parameter. The biasing current provided by the tail circuit of the VCO is adjusted based on the value of the digital control signal. In this way, the biasing current of the VCO may be adjusted to an optimal value for all frequencies of operation. The automatic control aspects of the present invention is useful in monolithic implementations since it automatically compensates for variations in load resistance, process parameters and component tolerances without requiring expensive manual adjustments at the board level.

Abstract: An apparatus comprising a first circuit and a capacitor circuit. The first circuit may be configured to generate an output signal having a frequency in response to (i) an input signal having a reference frequency and (ii) one or more adjustment signals. The capacitor circuit may be configured to adjust the frequency of the output signal. The one or more adjustment signals may provide constant current biasing of the first circuit.

Abstract: A voltage-controlled crystal oscillator (VCXO) has variable load capacitors on the crystal nodes. The variable load capacitors are p-channel or n-channel transistors with their source and drain nodes connected to a crystal node. The gates are driven by an input voltage that is generated from a full-swing control voltage by a voltage conversion circuit. The input voltage has a half-swing of only half of the power-supply voltage, or VDD/2. The input voltage driving n-channel capacitors swings from VDD to VDD/2, which is just above the source voltage of VDD/2 on the crystal node and ensures that the n-channel capacitors remain on for most of the range. A series of resistors can divide the input voltage into a series of differing voltages that drive gates of multiple n-channel capacitors that have their source/drains connected in parallel to the crystal node. Capacitance increases as an n-channel capacitor channel turns on.

Abstract: A harmonically damped oscillator circuit including a controllable oscillator amplifier for generating an oscillator output signal and including an amplitude control circuit for controlling the amplitude A of the oscillator output signal, an amplitude control signal Vcontrol being generated by the amplitude control circuit as a function of a determined amplitude A of the oscillator output signal in such a manner that the oscillator amplifier functions in a predefined operating range having an approximately linear amplification characteristic with a definable, small amplitude at a preset operating point, and the oscillator amplifier being designed in such a manner that the predefined operating range and the preset operating point are independent of the amplitude control signal Vcontrol. Thus, a stable amplitude loop for producing a low-distortion oscillator output signal can be achieved also under consideration of a comparatively large scatter range of the used component characteristics and parameters.

Abstract: A low consumption oscillator having an inverter connected to a high supply potential and to a low supply potential via two respective resistors, with the resistors formed of capacitors having strong leakages.

Abstract: A crystal-oscillator circuit includes an oscillation transistor having the collector or the base thereof at a ground potential. A first capacitor is connected between the base and the emitter of the oscillation transistor. A second capacitor is connected between the emitter and the collector. A quartz crystal resonator and a third capacitor are connected in series between the base and the collector. The third capacitor is disposed at the ground potential side. An oscillation signal is extracted from a node between the quartz crystal resonator and the capacitor.

Abstract: A novel circuit topology which provides for the digital automatic gain control of a VCO is disclosed. The topology of the VCO is based on the negative transconductance oscillator due to its intrinsically simple biasing scheme. A system parameter sensitive to the performance level of the VCO is firstly measured. A digital control signal is then generated in response to the measured system parameter. The biasing current provided by the tail circuit of the VCO is adjusted based on the value of the digital control signal. In this way, the biasing current of the VCO may be adjusted to an optimal value for all frequencies of operation. The automatic control aspects of the present invention is useful in monolithic implementations since it automatically compensates for variations in load resistance, process parameters and component tolerances without requiring expensive manual adjustments at the board level.

Abstract: A source-coupled oscillator contains two main MESFETs which supply current to respective loads and which have sources connected through a capacitor. Each of the main MESFETs is supplied with a constant current which can be adjusted to vary the frequency of the oscillator. The output signals are derived from the voltage across the loads. The oscillator also contains two differential pairs of MESFETs that change state as the main MESFETs are turned on and off and are connected so as to switch current into one or the other of the loads. Each of the differential pairs is supplied with a constant current. The currents supplied by the differential pairs act as compensating currents and are adjusted so that when the currents through the two main MESFETs are changed to vary the frequency of the oscillator, the total current through the loads remains constant.

Abstract: A source-coupled oscillator contains two main MESFETs which supply current to respective loads and which have sources connected through a capacitor. Each of the main MESFETs is supplied with a constant current which can be adjusted to vary the frequency of the oscillator. The output signals are derived from the voltage across the loads. The oscillator also contains two differential pairs of MESFETs that change state as the main MESFETs are turned on and off and are connected so as to switch current into one or the other of the loads. Each of the differential pairs is supplied with a constant current. The currents supplied by the differential pairs act as compensating currents and are adjusted so that when the currents through the two main MESFETs are changed to vary the frequency of the oscillator, the total current through the loads remains constant.

Abstract: There is disclosed an oscillator circuit in which the first capacitor is connected between the input side of a CMOS inverter in a quartz oscillator circuit and a higher potential side, the second load capacitor is connected between the input side of the inverter and a lower potential side, the third load capacitor is connected between the output side of the inverter and the higher potential side, and the fourth load capacitor is connected between the output side of the inveter and the lower potential side, so that variation in amplitudes of the voltage sources synchronized with the oscillation can be reduced with the realization of lower current consumption.

Abstract: A voltage-controlled oscillator comprises a level converting circuit, an amplitude controller, a voltage-controlled oscillation section having differential delay cells connected in a ring form, and an output level converting circuit. The level converting circuit has limiters which respectively limit a maximum value and a minimum value of a control current. Those limiters permit only a region where the voltage-controlled oscillation section properly performs its oscillating operation to be used.

Abstract: A crystal oscillator apparatus is described that has a wide dynamic frequency range and that is capable of supporting a broad range of crystal types. The present invention reduces the unwanted side effects that are associated with the prior art crystal oscillator designs, such as the clipping of signals, the introduction of signal distortion and unwanted signal harmonics. The present invention reduces the total wasted loop gain of the oscillator while also reducing the amount of integrated circuit real estate required to implement the crystal oscillator. The crystal oscillator apparatus of the present invention preferably comprises a crystal resonator circuit, an inverting amplifier, a bias circuit, a reference circuit, and a peak detector circuit. The present invention takes advantage of Automatic Gain Control (AGC) design techniques. The gain of the present crystal oscillator is automatically regulated using a closed loop circuit design.

Abstract: Voltage controlled oscillator assembly, comprising at least one voltage controlled oscillator, and means for regulating the output power from the at least one voltage controlled oscillator.

Abstract: A piezoelectric oscillator which is excellent in noise characteristic and aging characteristic is implemented by a piezoelectric oscillator comprising: a Colpitts oscillator including a piezoelectric resonator and an oscillation transistor; amplification means for amplifying an output of the Colpitts oscillator; and rectification means for rectifying an output of the amplification means, an output of the rectification means being fed back to base of the oscillation transistor to keep an oscillation output level constant, in which a base bias is set so as to provide the oscillation transistor with an operation point located in the vicinity of a saturation region, and in which a feedback current from the rectification means is supplied to the base of the oscillation resistor so as to make the operation point approach to the saturation region when the saturation output level has become high and so as to make the operation point go away from the saturation region when the oscillation output level has become low.

Abstract: The voltage controlled oscillator (VCO) of the present invention generally includes a energy storage circuit portion, an oscillator operably connected to the energy storage circuit portion, a varactor connected to the oscillator and energy storage circuit portion, and an amplitude controller that is operably connected to the energy storage circuit portion, oscillator, and varactor. The energy storage circuit portion includes an inductance and a capacitance. The oscillator provides an oscillating output signal having a frequency and an amplitude. The varactor has a capacitance and receives an input signal having a varying level. The capacitance of the varactor varies according to the level of the input signal. The amplitude controller sets the amplitude of the oscillating output signal. Meanwhile, the inductance of the energy storage circuit portion, the capacitance of the energy storage circuit portion, and the varying capacitance of the varactor are used to set the frequency of the oscillating output signal.

Abstract: An inductive proximity sensor oscillator having a differential comparator in combination with a negative feedback network and a positive feedback network connected to the comparator. The positive feedback network determines the frequency and amplitude of the generated oscillations. An LC resonant tank circuit is connected between a non-inverting input and a fixed reference voltage, and a current limiting resistor connected between the non-inverting input and the output of the comparator. The negative feedback network provides a simple, fast and reliable start-up mechanism. It comprises a capacitor connected between the inverting input of the comparator and the circuit ground and a resistor connected between the non-inverting input and output of the comparator.

Abstract: An oscillator having an adjustable gain circuit provides abundant gain when the oscillator is first powered up but reduces the gain substantially below its start-up value once oscillations build up, thereby substantially reducing the power consumed. The oscillator comprises an inverting amplifier coupled to a resonator, an oscillation detector coupled to the inverting amplifier amplifier, and a common-gate amplifier coupled to the oscillation detector. The inverting amplifier amplifies oscillations of the resonator according to a gain. The oscillation detector outputs a detection signal in response to oscillations of the resonator. The level of the detection signal is proportional to the amplitude of the oscillations. The common-gate amplifier receives the detection signal and, in response, limits the current to the inverting amplifier to control the gain based on the level of the detection signal.

Abstract: A crystal oscillation circuit that is capable of operating stably with a low power consumption includes a signal inversion amplifier and a power control circuit that controls the power voltage of this signal inversion amplifier in accordance with an oscillation output. The power control circuit includes a power voltage generation circuit that outputs a plurality of power voltages of different values; a determination control portion that determines the optimal value of the power voltage to be applied to the signal inversion amplifier, based on the oscillation output; and a multiplexer that controls the switching of the power voltage applied to the signal inversion amplifier from the power voltage generation circuit, based on the result of that determination.

Abstract: A circuit for controlling the loss of a VCO in a master-slave tuning system includes an envelope detector, an amplitude regulator, a current-mode circuit, and a low-pass filter. The envelope detector receives the VCO output voltage and provides VCO output envelope voltage, V.sub.ENV. The amplitude regulator receives V.sub.ENV and a reference voltage, V.sub.REF, and provides a sourcing current if V.sub.ENV is less than V.sub.REF, and draws a sinking current if V.sub.ENV is greater than V.sub.REF. The current-mode circuit receives V.sub.ENV and provides a control current, I.sub.Q. The low-pass filter has high DC gain for integrating the control current and the sourcing or sinking current to provide the VCO control voltage, V.sub.CON, to the VCO. The control current, I.sub.Q, is proportional to the inverse of V.sub.ENV multiplied by the time derivative of V.sub.ENV.

Abstract: A crystal tank circuit is connected between the ac cross-coupled outputs of two transistors that are selectively biased to an appropriate common mode voltage to cause rapid build-up of oscillation when the circuit is turned on and in which oscillation is sustained in the desired mode regardless of battery voltage fluctuation without wasting power. The differentially driven frequency-controlling crystal tank circuit receives balanced driving voltage excursions from the circuit.

Abstract: A drive circuit for an oscillator having an LC tank reduces phase noise by maximizing the oscillation amplitude and minimizing the drive to the tank. The drive circuit utilizes a capacitive attenuator network for level shifting the oscillation signal before feeding it back to the drive transistors in the drive circuit, thereby allowing a large peak voltage swing across the tank without saturating the transistors. An adaptive control circuit controls the biasing of the drive transistors and reduces the drive to the tank when the maximum oscillation amplitude is reached so that the drive circuit replenishes just the minimum amount of energy lost in the tank during each cycle, thereby minimizing the coupling of active circuit noise into the tank.

Abstract: A highly stable single chip crystal controlled oscillator with automatic gain control. An amplitude detector monitors the output of a crystal controlled oscillator amplifier and produces a feedback signal proportional to the output signal of the amplifier to ensure oscillation is induced at startup and that the amplitude of oscillation is limited to a preselected value during operation to conserve power consumption by the amplifier. The capacitor tank circuit connected to the input of the amplifier includes a voltage variable capacitor the voltage across which is initially established at manufacture to tune the oscillation frequency to a preselected value. The voltage across the voltage variable capacitor is also adjusted to compensate for temperature variations in the circuit.

Abstract: There is disclosed an oscillator circuit comprising the first load capacitor with one electrode there of being connected with an input side of a CMOS inverter within a quartz oscillator circuit, and the second load capacitor with one electrode there of being connected with the output side of the inverter, wherein the inverter is coupled to a lower potential side via a current-limiting device, and the other electrodes of the first and second load capacitors are coupled to a lower potential side via the above-described current-limiting device. Thus, variations in the power-supply voltages synchronized with oscillation are reduced with realization of lower current consumption.

Abstract: A quadrature oscillator based on two cross-coupled gm/C cells utilizes the inherent nonlinearity of positive and negative impedance cells to control the amplitude of oscillation, thereby simplifying the oscillator and eliminating the need for an outer control loop. The oscillator includes a pair of cross-coupled gm/C stages. A negative impedance cell is coupled to each gm/C cell for assuring proper start-up and enhancing the amplitude of oscillation. A positive impedance cell is also coupled to each gm/C cell to dampen the amplitude of oscillation. The transconductance of each impedance cell varies in response to the bias current provided to the cell. Thus, by controlling the bias currents through the cells, the negative and positive impedances seen by each gm/C cell can made to cancel at the desired oscillation amplitude, so that the circuit oscillates without any damping or enhancement.

Abstract: A crystal oscillator drive circuit controls the maximum amplitude of the drive signal to a crystal by limiting the bias current of a gm cell which senses the oscillation amplitude of the crystal. The bias current is commutated by the gm cell responsive to the crystal oscillation. The commuted current is converted to a single-ended current by a current mirror. An output stage converts the current to an output voltage having a voltage swing that is determined by the resistance of a load resistor. The output voltage is then fed back to drive the crystal through a positive feedback path. The output voltage swing and the drive signal to the crystal are limited by the bias current of the gm cell. A fully complementary implementation of the drive circuit includes two complementary gm cells, two current mirrors, and an output stage having two load resistors.

Abstract: A ring oscillator with differential delay stages employs an automatic gain control circuit producing a gain adjust signal that is responsive to a frequency control voltage applied to the ring oscillator. The effect of the frequency control voltage on the output voltage of the ring oscillator is counterbalanced by the gain adjust signal which prevents the output voltages of the delay stages from varying excessively over frequency. Further, the output stage of the ring oscillator includes shut off circuitry that allows the ring oscillator to be shut off in a non-oscillating mode in which it draws little current.

Abstract: A method is presented for minimizing the current consumption and the operating voltage of a voltage controlled oscillator. According to the invention the oscillator's (Q2) output signal (RFout) is detected as a DC voltage signal (Vgs) in a clamp/voltage multiplier circuit (U1, U2), preferably after a isolating amplifier (Q1). This detected signal is supplied in a feedback loop to a field effect transistor (FET1) controlling the oscillator's (Q2) current, whereby the field effect transistor controls the current (Ib) in the main current path to a predetermined minimum value. In this superimposed arrangement of the oscillator and the isolating amplifier the supply voltage (B) can be minimized by arranging, regarding the DC current, the isolating amplifier (Q1) in parallel with the field effect transistor (FET1) in the emitter branch of the oscillator (Q2).

Abstract: Supplied with a power source, an output level of an oscillating circuit gradually increases until the oscillator circuit reaches its steady oscillation. A level monitor monitors the output level, and produces a control signal if the output level is less than a predetermined level. A current producing circuit receives the control signal and produces a boost current to increase a collector current at an oscillating transistor. The output level of the oscillating circuit suddenly increases as the collector current increases. After the output level of the oscillator reaches the predetermined level, the level monitor stops production of the control signal. Therefore, the boost current stops. As a result, the collector current of the oscillating transistor has a predetermined value dependent on the circuit structure of the oscillating circuit.

Abstract: A bipolar negative resistance UHF oscillator having a voltage tunable resonator in its emitter circuit is operated at a fixed collector bias current and an RF detector is used as a convenient way to determine the RF current at which the oscillator is operating, by sensing the amplitude of the oscillator's output RF voltage across a constant load. An integrating error amplifier referenced to a desired detector output level responds to the actual detector output level to control the collector bias voltage for the oscillator and maintain the output of the oscillator at a fixed amplitude. Since the collector bias current is fixed, this keeps the operating point at fixed relation with respect to emitter cutoff. That relationship is chosen to be "just below" by initial selection of the constant collector bias current and the reference voltage used by the integrating error amplifier.

Abstract: An oscillator in which the transconductance of an amplification transistor (T0) is limited through a measurement of the potential at the input electrode (G0) of the amplification transistor (T0) by means of a differential pair (T1, T2) for safeguarding the starting of the oscillator.

Abstract: An oscillator provided with an amplitude controller (AMPREG1) which is coupled by an input (G1) to an amplitude reference terminal (AMPREF1). The amplitude of the oscillator signal at the output terminal (KU) can be adjusted through coupling of a voltage-generating means to the amplitude reference terminal (AMPREF1).

Abstract: An oscillator circuit is provided for stabilizing the amplitude of a HF oscillation of an audio signal. In such an oscillator circuit, an audio signal having a frequency in the range of 20 Hz . . . 20 kHz is coupled into the oscillator circuit, is modulated with a high frequency and is emitted in the form of an RF audio signal having a frequency of more than 2 MHz. Such an oscillator circuit is used for instance in an infrared transmitting unit, wherein a low frequency audio signal is transformed into a higher frequency infrared signal. The higher frequency audio signals are transmitted via infrared channel to an appropriate receiving unit--for instance to infrared head phones--which comprises a receiving unit having an appropriate demodulator and preferably also a stereo-decoder in order to reproduce the low frequency audio signals.

Abstract: A low power, fast starting oscillator (10) of the Colpitts type includes an amplifier (12) that provides voltage gain and feeds a source follower circuit (14) that provides a desirable output impedance. A crystal (16) is coupled from an output of the source follower circuit (14) back to the amplifier's input (32). The voltage gain of the amplifier (12) and the output impedance of the source follower circuit (14) are independently selectable to provide an optimum transconductance for the oscillator (10) to start quickly. When oscillations reach a threshold value, the transconductance may be reduced to save power.

Abstract: A low power consumption oscillator circuit is provided with an oscillator. The oscillator responds to a voltage by producing an oscillating signal at its output having an amplitude that depends on the level of the voltage. Furthermore, the low power consumption oscillator circuit has a level shifter. Illustratively, according to one embodiment, the level shifter includes a pull-up driver and a pull-down driver connected in parallel between the oscillator output and an output of the level shifter. The pull-up driver is configured so as to refrain from conducting current between a biasing input of the pull-up driver and the level shifter output simultaneously with the pull-down driver when the oscillating signal exceeds a certain voltage level. The level shifter illustratively includes an intrinsic PMOS device.

Abstract: A quadrature oscillator includes an amplitude control circuit that is based upon the trigonometric identity sin.sup.2 .omega.t+cos.sup.2 .omega.t=1. The amplitude control circuit, referred to as a Pythagorator, includes two squaring circuits. Each squaring circuit receives a respective quadrature oscillator signal and squares it. The outputs of the two squaring circuits are joined together so as to sum the outputs of the two squaring circuits to produce a sum of squares signal. This signal, a current in the preferred embodiment, is provided to damping diodes coupled to the outputs of the quadrature oscillator. The damping diodes produce a shunt positive resistance at the outputs of the quadrature oscillator in response to this current that has the effect of cancelling the shunt negative resistance of the regenerative elements of the oscillator thereby establishing the amplitude of the quadrature oscillator signals at a desired amplitude.

Abstract: A method is described for maintaining a constant Q in a voltage controlled oscillator (VCO) which is tuned over a broad frequency band. A tank circuit (111) sets a center frequency of an oscillator circuit (112). A variable reactance circuit (113) provides a variable effective reactance across the tank circuit (111) corresponding to an applied tuning voltage (117) for tuning the VCO. Resistive currents from the variable reactance circuit are rectified by a rectification circuit (120). A comparator produces a Q control voltage corresponding to the rectified resistive currents and a reference current Iref at a terminal (126) which is coupled to a variable resistance circuit (122) for supplying differential resistive currents to the tank circuit (111) which offset the resistive currents from the variable reactance circuit, thereby maintaining a constant Q in the VCO.

Abstract: An option select scheme (300) and circuit (200) allows a single analog-to-digital (A/D) line (211) to be used between an accessory (204) and a portable radio (202) to control first and second accessory features (234, 236). First and second variable resistive devices (226,228) are used in conjunction with a push-to-talk switch (PTT) (230) to control the first and second accessory features (234, 236). The PTT switch (230) allows the first variable resistive device (226) to present a first voltage range to the A/D line (211) in a first state when the PTT switch (230) is depressed. The PTT switch (230) allows the second variable resistive device (228) along with bias resistor (224) to present a second voltage range to the A/D line (211) in a second state when the PTT switch (230) is not depressed. A third state exists when the accessory (204) is disconnected from the radio (202) and a third voltage range is presented to the A/D line (211).

Abstract: An automatic gain control circuit and method ensure feedback for oscillator circuitry fabricated on a single semiconductor chip to adapt to the Q value established by a resonator circuit connected to the oscillator circuitry, and to ensure that gain is maximized and linearity of operation preserved within the voltage rails of the power supply.