Abstract: A multi-point electrical probe for testing location-specific electrical properties on circuit boards. Four generally parallel, electrically conducting probe arms are produced preferably by wafer-based techniques, although any even number of probe arms between two and 64 may be used. The precision of wafer-based manufacturing techniques permits miniaturization beyond that which is conventionally obtained by assembling discrete components. The probe arms are generally flexible, and may be shaped suitably to accommodate a particular circuit geometry. The probe and/or the sample under test may be precisely located by suitable translation and/or rotation stages, which may optionally be placed under computer control. A suitable wiring diagram is provided, and preferable manufacturing techniques are discussed.

Abstract: A method of and testing jig for sequentially testing front and rear surfaces of a semiconductor chip is shown. The testing jig includes a support package having a first cavity over which the semiconductor chip mounts; an infrared filter affixed relative to the first cavity and attached to a rear surface of the semiconductor chip; and a test substrate having a second cavity exposing the infrared filter and upon which the support package mounts. Front and rear surfaces of the semiconductor chip can be conveniently and sequentially tested. Because the testing jig includes the infrared filter and the heat pad, heat can be easily transmitted to the defective chip.

Abstract: In one embodiment, a probe for probing test points on a target board includes a printed circuit board, a frame, and a plurality of spring pins. The printed circuit board (PCB) has a first side with a plurality of solder pads thereon, and a plurality of signal routes that are electrically coupled to the solder pads for routing signals to a test instrument. The frame is mechanically coupled to the PCB and has a main body portion with a plurality of holes therein. The holes in the frame are aligned with the plurality of solder pads on the first side of the PCB. The plurality of spring pins are provided for probing the test points on the target board, with each spring pin being i) disposed in one of the holes in the frame, perpendicularly abutting the first side of the PCB, and ii) electrically coupled to one of the solder pads. Other embodiments, including a method of making a probe, are also disclosed.

Abstract: A probe device includes a tester; a probe card; a base card holder; an auxiliary card holder for adaptively mounting the probe card to the base card holder; and a conversion ring for allowing the auxiliary card holder to be fitted to the base card holder. In the probe device, the base card holder is configured to accommodate any one of selected different conversion rings and the conversion ring is the one chosen from the different conversion rings according to the probe card.

Abstract: A needle alignment verification circuit includes a sensor pad, a first transmission line, a control element, a data pad, a second transmission line, and a response element. The sensor pad includes an insulation part and a conduction part. The first transmission line is electrically connected to the conduction part and to the interior of the semiconductor device. The control element asserts the first transmission line at a first logic state, and upon receiving the probe signal at the conduction part, transitions the logic state of the first transmission line to a second logic state. The second transmission line provides a predetermined signal to the data pad. The response element controls the second transmission line so that the second transmission line has the state of a verification result voltage for a misalignment state in response to the second logic state.

Abstract: A low-current pogo probe card for measuring currents down to the femtoamp region includes a laminate board having a layer of conductive traces interposed between to dielectric layers. A plurality of probing devices, such as ceramic blades, are edge-mounted about a central opening so that the probing needles or needles included therein terminate below the opening in a pattern suitable for probing a test subject workpiece. A plurality of pogo pin receiving pad sets, each including a guard pad, occupy the periphery of the board. Each guard pad is electrically connected to a trace from the layer of conductive traces. The pad sets may be connected to the probing devices by low noise cables or traces. Air trenches separate the pad sets for reducing cross talk and signal settling times.

Abstract: A circuit for isolating a short-circuited integrated circuit (IC) formed on the surface of a semiconductor wafer from other ICs formed on the wafer that are interconnected with the short-circuited IC includes control circuitry within the short-circuited IC for sensing the short circuit. The control circuitry may sense the short circuit in a variety of ways, including sensing excessive current drawn by the short-circuited IC, and sensing an abnormally low or high voltage within the short-circuited IC. Switching circuitry also within the short-circuited IC selectively isolates the short-circuited IC from the other ICs on the wafer in response to the control circuitry sensing the short circuit. As a result, if the wafer is under probe test, for example, testing can continue uninterrupted on the other ICs while the short-circuited IC is isolated.

Abstract: In one embodiment, a mock wafer for calibrating automated test equipment includes a printed circuit board having a number of interconnect areas, with each interconnect area having a pair of mock die pads that are coupled via a connecting trace. In another embodiment, a method for calibrating automated test equipment (ATE) may include coupling the mock wafer to the ATE, and then causing the ATE to i) index the mock wafer with respect to a test head connector, ii) couple a number of probes or the test head connector to a number of the mock wafer's mock die pads, iii) transmit a test signal between a pair of the probes that are coupled via a pair of mock die pads and connecting trace of the mock wafer, and iv) calibrate a selected signal path or paths of the ATE by recording a characteristic of the transmitted test signal.

Abstract: Circuitry for driving a pin includes a first resistive circuit connected to the pin, a first transistor circuit to connect the first resistive circuit to a logic level voltage in response to a trigger voltage, the first transistor circuit and the first resistive circuit together defining a termination impedance, and a driver circuit to apply the trigger voltage to the first transistor circuit. The driver circuit includes counterparts to the first resistive circuit and the first transistor circuit. The counterparts define a counterpart impedance that is controlled to control the trigger voltage and thereby control the termination impedance.

Abstract: According to one embodiment of the invention, a method for resuming the probing of a wafer includes identifying a data set associated with a wafer. The data set identifies at least one unprobed die supported on the surface of the wafer. The method also includes determining that the data set associated with the wafer is useable and generating a probe map of the wafer from the data set. The probe map identifies a physical position associated with each unprobed die supported on the surface of the wafer. The probe map and one or more probe commands are communicated to a probe module to drive the probe module in resuming the probe of the wafer.

Abstract: A semiconductor memory device includes a reference signal generating unit for generating a reference signal; a comparing unit for comparing the reference signal with a test signal applied to a test pad to output an adjusted value after adjusting the adjusted value until the test signal is equal to the reference signal; an impedance measuring unit for measuring an impedance of the test pad based on the adjusted value to output the test signal; an impedance adjusting unit for adjusting an impedance of a data I/O pad to have an impedance value corresponding to the adjusted value outputted when the test signal is equal to the reference signal; an impedance control unit for controlling the comparing unit so that the adjusted value is outputted when the test signal is equal to the reference signal; and a reference signal control unit for adjusting a voltage level of the reference signal.

Abstract: A plurality of sets of circuits are provided, each of which generates an impedance code through the use of an impedance control circuit in association with a resistive element connected to an external terminal, and each of which varies the impedance in accordance with such an impedance code. The impedance control circuit includes an impedance comparator which is formed equivalently to the resistive element and the plurality of sets of circuits, and which performs an impedance comparison with each of a plurality of replica circuits to form an up signal that increases the impedance and a down signal that decreases the impedance. Counters are provided adjacent to the individuals of the plurality of sets of circuits to thereby generate the impedance codes in response to the up signal and the down signal.

Abstract: A logic element includes memory elements, multiplexers, and controls. The multiplexers are arranged in levels including a highest level of multiplexers with inputs connected to the memory elements and outputs connected to inputs of a next-to-highest level of multiplexers and a first level of multiplexers with inputs connected to outputs of a second level of multiplexers and at least one output. The controls are connected to the multiplexers. In a first operational mode the controls determine a first-mode output at the at least one output of the first level of multiplexers, and in a second operational mode the controls determine a plurality of second-mode outputs at selected outputs of multiplexers not at the first level of multiplexers.

Abstract: The present invention is directed to a soft core logic circuit implemented in a PLD that estimates an appropriate phase delay and applies the phase shift to a read strobe signal to align its rising and falling edges at the center of a data sampling window associated with a group of read data signals. The soft core logic circuit dynamically determines an appropriate phase-shift value for the read strobe signal and adjusts the phase-shift to accommodate the environmental changes. The soft core logic circuit also introduces into the PLD various intermediate signals from a phase-shift estimator and a programmable phase delay chain.

Abstract: A read out device for reading out a data word from a memory cell is described. The read out device has memory cells, inputs for input variables for selecting a memory cell and a hierarchical arrangement of multiplexers having N hierarchical levels. The control inputs of the multiplexers of a hierarchical level are connected to an input, the inputs of the hierarchical arrangement of multiplexers are connected to the outputs of the memory cells and the number of memory cells is less than 2N.

Abstract: A programmable semiconductor device, wherein: a user programmable switch comprising a configurable element is positioned above a transistor gate material layer deposited on a silicon substrate layer.

Abstract: Provided are a simultaneous bi-directional (SBD) buffer including a self-test circuit having a function of generating an input signal. By using the self-test circuit, self-testing can be accurately performed by generating the input signal in a self-test mode, and a self-test method used by the SBD buffer. The SBD buffer includes an output driver, an input receiver, a first multiplexer, and an input signal generating circuit. The output driver receives an output data signal and outputs the received output data signal to an input/output node. The input receiver receives a signal generated by combining an input data signal inputted to the input/output node with the output data signal, compares the voltage level of the signal with a reference voltage, and outputs the comparison result. The first multiplexer outputs the reference voltage in response to a reference voltage selection signal.

Abstract: Embodiments for controlling pre-emphasis driver circuits for electrical signal interconnects within a computer system are disclosed.

Abstract: A cascaded pass-gate test circuit including interposed split-output drive devices provides accurate measurement of critical timing parameters of pass gates. The rise time and fall time of signals passed through the pass gate can be separately measured in a ring oscillator or one-shot delay line configuration. Inverters or other buffer circuits are provided as drive devices to couple the pass gates in cascade. The final complementary tree in each drive device is split so that the only one of the output pull-down transistor or pull-up transistor is connected to the next pass gate input, while the other transistor is connected to the output of the pass gate. The result is that the state transition associated with the device connected to the pass gate input is dominant in the delay, while the other state transition is propagated directly to the output of the pass gate, bypassing the pass gate.

Abstract: A method extends a clock-gating technique to provide a sleep signal for controlling switch circuits that reduce active leakage power. Using this extension of the clock-gating technique, fine-grained power-gating is achieved. The method automatically identifies, at an RTL or a gate level, the logic circuits that can be power-gated. The method of the present invention derives a sleep signal for fine-grained power-gating that may be applicable to both time-critical and non-time-critical designs.

Abstract: Circuit arrangement for producing a dual-rail output signal having a signal processing apparatus with two switches, which are driven as a function of an input signal, a first output connected via one of the switches to a signal processing apparatus foot point, which is at a first potential, and a second output connected via the other switch to the foot point. The signal processing apparatus is connected via a switching apparatus to outputs of the circuit arrangement in order to output a dual-rail output signal. The outputs of the switching apparatus are each connected to one or to both inputs of the switching apparatus as a function of a control signal. A potential monitoring apparatus defines the potentials at the outputs of the circuit arrangement when these outputs are not connected via the switching apparatus and the signal processing apparatus to the foot point of the signal processing apparatus.

Abstract: A differential sense amplifier is described that can be configured as a preamplifier or a latch circuit as triggered by a clock signal connected to a switch circuit. When the clock signal is set at a first signal level, the switch circuit in the differential sense amplifier is activated so that the differential sense amplifier is configured as a preamplifier with a positive feedback circuit. When the clock signal is set at a second signal level, the switch circuit in the differential sense amplifier is deactivated so that the differential sense amplifier is configured as the latch circuit. For one read cycle, the differential sense amplifier operates first as the preamplifier and then as the latch circuit.

Abstract: A half-bridge driver includes first and second power switches, connected with their respective current paths in series, a pulse generator for generating a voltage pulse waveform, arranged to drive the first power switch, a first current generator for generating a current pulse for each negative flank of the voltage pulse waveform, a second current generator for generating a current pulse for each positive flank of said voltage pulse waveform, and a differential current receiver circuit. The differential current receiver circuit is connected to the first and second current generators, and is arranged to generate an output signal equal to the difference of the currents flowing through the current generators. The output signal is arranged to drive the second power switch.

Abstract: A multiphase divider includes a plurality of resetable dividers configured for performing resetable divider stages to a plurality of multiphase signals forming a plurality of divided multiphase signals having a monotonic increasing phase with equal spacing and an ideal duty cycle of 50%, wherein the plurality of divided multiphase signals have no phase ambiguity; and a reset signal generator configured for producing a plurality of periodic reset signals to the plurality of resetable dividers to enable the plurality of resetable dividers to divide the plurality of multiphase signals in a timely correct sequence to form the divided multiphase signal, the plurality of periodic reset signals being produced by a combinational network of the reset signal generator, the combinational network is configured for generating a number of pulses based on the plurality of multiphase signals and performing decimation stages to reduce the number of pulses within the pulse traces.

Abstract: Adverse effects of switching noise produced by a charge pump circuit on a displayed image are prevented. In a synchronizing separation circuit 18, a synchronizing signal is separated from a video signal. The separated synchronizing signal is subjected to ½ frequency division in a flip-flop 20 to obtain a clock signal having a period which is two times as much as one horizontal period, and this clock signal is utilized to control switching of the charge pump circuit. As a result, a timing at which each switch in the charge pump is changed over can be set in a period close to a horizontal synchronizing signal without a video signal, thereby preventing noise from affecting the video signal.

Abstract: A DLL includes a control module coupled with a phase detect signal. The phase detect signal is used by a control module to generate feedback and output select signals. The feedback and output select signals are each coupled to a multiplexer. Each multiplexer is coupled to a Multi-Tap Delay Line (MTDL). The MTDL provides a plurality of delayed signals that are selectable by the two multiplexers. The first multiplexer, coupled to the feedback select signal, selects a feedback clock signal. The second multiplexer, coupled to the output select signal, select a DLL output signal. The control module may receive other signals, such as a delay select signal, that may be used to program or set the delay of the output signal. In addition, a plurality of output signals may be available from the DLL.

Abstract: A frequency synthesis circuit includes a phase locked loop and an interpolator circuit. The phase locked loop circuit receives a reference clock and a feedback clock and generates an output clock with a frequency based on the reference clock and the feedback clock. An interpolator circuit is coupled in the feedback path of the phase locked loop circuit. An interpolator control circuit generates an interpolator control word that specifies a variable time delay for the interpolator circuit. The interpolator circuit receives the output clock, and generates the feedback clock by introducing a variable time delay in the output clock in accordance with the interpolator control word. The time variable delay varies the frequency of the output circuit. Embodiments for frequency synthesis circuits that include a spread spectrum frequency clock generator, frequency modulators, and a fixed frequency clock generator circuit are disclosed.

Abstract: An apparatus and method of synthesizing an output clock signal from a source clock signal. The clock synthesizer includes a phase generator, a phase selector, a phase interpolator, and control circuitry for controlling the phase selector/interpolator. The phase generator receives a high speed clock, and generates P phases of the source clock to define P phase sectors. The phase selector selects respective pairs of phases such that each pair bounds a respective phase sector. The phase interpolator introduces at least one phase of the source clock between each pair of phases to provide Q phases of the source clock within each sector. The phase interpolator uses the phases of the source clock to produce lagging (leading) phase shifts of 360/P(Q?1) degrees, thereby generating the output clock having a stepped up or stepped down frequency.

Abstract: A delay-locked loop (DLL) circuit with mutual-interpolating architecture that provides multiple-phase clock generation is presented. Each delay-cell in the DLL circuit delay chain is effectively an interpolator that combines two input clock signals: one input clock signal is received from the output clock of previous stage in the delay chain, and the other input clock signal is fed back from a following stage. Each delay cell supports the concurrent functions of delay and interpolation. The architecture imposes a set of N simultaneous equations, where N is the total number of delay clock signals, to control the clock waveforms. These simultaneous equations obtain a unique solution when the DLL enters a lock state, and the generated delay clock signals inherently have a clock duty cycle of 50%. The delay chain can be implemented using either odd or even number of delay cells.

Abstract: Pulse-width modulation (PWM) circuits and methods integrate a feedback signal and an input signal to generate an integral signal, and generate a PWM signal by switching an output node from a first source voltage to a second source voltage based upon comparing the integral signal with a first reference voltage, and switching the output node from the second source voltage to the first source voltage based upon comparing the integral signal with a second reference voltage. A comparator unit compares the integral signal with the first and second reference (threshold) voltages, and a drive circuit for buffering the comparator unit's output signals generates drive signals. A feedback circuit generates the feedback signal based on (e.g., proportional with) the PWM signal. The switching circuit may include a P-type switch (e.g., PMOS transistor) and a N-type switch (e.g., NMOS transistor). Associated class-D audio amplifiers and modulation methods are provided.

Abstract: In a preferred embodiment, the invention provides a circuit and method for reducing soft error events in latches. A low-pass filter is placed between the output of a forward inverter and the inputs of a feedback keeper. The first and second outputs of the low-pass filter are connected to first and second inputs respectively of the feedback keeper. The only type of diffusion connected to the first output of the low-pass filter is a P-type diffusion. The only type of diffusion connected to the second output of the low-pass filter is an N-type diffusion. The feedback keeper is connected to an input of the forward inverter.

Abstract: A system on a chip integrated circuit includes a first circuit module and N other circuit modules that are operable to produce at least one output signal based on at least one input signal. A reference oscillator for generating a base clock signal for the first circuit module. A clock delay generator generates N delayed clock signals at a corresponding N clock delays, wherein N is greater than or equal to 2. The N delayed clock signals are provided to the N other circuit modules.

Abstract: A signal processing system has a first, digitally controlled, gain element, a second, analogue controlled, gain element and a gain control unit configured to receive a gain request signal and to generate a first gain control signal to be input to the first gain element and a second gain control signal to be input to the second gain element such that the gain provided by the signal processing system corresponds to the gain request signal.

Abstract: A driver circuit is provided for preventing generation of a pass-through current in a CMOS output unit even if a power supply voltage VDD supplied from a low voltage power supply drops below a recommended operating power supply voltage. The driver circuit includes a level shift unit having PMOS transistors and NMOS transistors, and a CMOS output unit having a PMOS transistor and an NMOS transistor. The source, drain and gate of one PMOS transistor are respectively connected to a high voltage power supply, a first contact and a second contact. The source, drain and gate of a second PMOS transistor are respectively connected to a high voltage power supply, the second contact and the first contact. The source of one NMOS transistor is grounded, the drain thereof is connected to the first contact, and the gate thereof receives a low voltage signal. The source of a second NMOS transistor is grounded, the drain thereof is connected to the second contact, and the gate thereof receives a low voltage signal.

Abstract: A low-power consumption level shifter circuit is provided by preventing a through current which is generated when a level of a signal is changed. In order to prevent a through current which flows when a level of a signal of the input is changed, the p-channel TFTs are controlled so that the p-channel TFTs and the n-channel TFT or the p-channel TFTs and the n-channel TFT are not turned on at once. A high level signal is inputted to the gate of the n-channel TFT, and at the moment when the n-channel TFT is turned on, the p-channel TFT is turned off. Similarly, at the moment when the n-channel TFT is turned on, the p-channel TFT is turned off. The p-channel TFTs and the n-channel TFT, or the p-channel TFTs and the n-channel TFT are not turned on at once, thereby a path in which the through current flows is cut off.

Abstract: A fuse-based cell and method of operation are described. The method includes programming a fuse to have a programmed state using a programming voltage that is greater than a supply voltage and sensing the programmed state of the fuse using a sense device. The method also includes providing bias current to the sense device using a load and isolating the sense device and the load from exposure to a full potential difference between the supply voltage and the programming voltage during the programming of the fuse.

Abstract: A charge pump circuit comprises a first pump stage, including a first sub-pump coupled to a first pre-charge MOSFET transistor, wherein the first sub-pump is used to pump down a gate of the first pre-charge MOSFET transistor to thereby increase the pre-charge efficiency of the first pre-charge MOSFET transistor. The higher efficiency the pre-charge MOSFET is, the lower the gate level of a pass transistor is. Thus, the charge sharing efficiency becomes better, and the body effect will be eliminated. The following pump stage is the same as the first pump stage. In addition, this pre-charging is implemented by PMOSFET only; therefore, only a single well is needed and then a small layout area can be achieved. Consequently, a high efficiency negative pump can be obtained.

Abstract: An integrated charge pump is provided, comprising: a pump capacitor having a first terminal and a second terminal; a control unit, which operates the charge pump in an alternation between a first phase and a second phase; a first switching device in order to charge the pump capacitor with a pump voltage in the first phase; a second switching device in order to pull the potential of the first terminal to a predetermined potential in the second phase, and in order to connect the second terminal of the pump capacitor to an output node, the second switching device having a first transistor in order to connect the second terminal of the pump capacitor to the output node, a substrate terminal of the first transistor being fixedly connected to the output node; and the second switching device pulling the first terminal to the predetermined potential with a gradient, the gradient being chosen such that at no point in time is a diode breakdown voltage exceeded in the first transistor.

Abstract: An integrated circuit providing high equivalent capacitance ranging from a few tens of picofarads to a few nanofarads is presented. The integrated circuit includes active integrated circuit components, requires no external capacitor, and is substantially insensitive to transistor current gain variations. The high capacitance integrated circuit can be advantageously used to provide, for example, timing delay and servo loop compensation.

Abstract: An apparatus for biasing a transistor, comprising: a controllable bias generator; a test circuit; a digital Mth order differentiator responsive to an output of the test circuit; and a controller responsive to the digital Mth order differentiator for controlling the controllable bias generator; wherein the test circuit is configured to calculate an Lth order derivative of the transistor's performance.

Abstract: An amplifier circuit comprises a first amplifier having an input and an output. A second amplifier has an input that communicates with an output of the first amplifier. A third amplifier has an input that communicates with an input of the first amplifier. A fourth amplifier has an input that communicates with an output of the third amplifier and an output that communicates with the input of the second amplifier. A switched capacitance circuit selectively couples a capacitance to at least one of the input of the third amplifier and the output of third amplifier.

Abstract: A method and apparatus are provided for operating a feedback network (300, 400). The method and apparatus operate to combine (240) a feedback signal (IF) and an incoming signal (VIN) to generate an adjusted signal (IADJ) at an input node of an amplifier element (110); amplifying the amplifier input signal in the amplifier element to produce an amplifier output signal (VOUT) at an output node of the amplifier element; processing the amplifier output signal according to a feedback operation (230) to generate the feedback signal (IF); and providing an assist current (350, 450, IASSIST) to the output node of the amplifier element, separate from an output current provided by the amplifier element.

Abstract: A differential amplifier formed on a silicon-on-insulator substrate, including means to prevent the bodies of its differential input transistors from charging to unwanted potentials in the standby state. In one aspect of the invention, the means takes the form of switching transistors inserted between the differential input transistors and their loads. In another aspect of the invention, the means takes the form of switching transistors inserted between the sources and bodies of the differential input transistors. In another aspect of the invention the means is a regulator section that holds the bodies of the differential input transistors at an appropriate potential level.

Abstract: Variable attenuation systems having continuous input steering may be used to implement vector or quadrature modulators and vector multipliers. Discrete implementations of attenuators with continuous input steering may have two outputs which may be cross-connected to provide four-quadrant operation. A symmetrically driven center tap may provide improved zero-point accuracy.

Abstract: An operational transconductance amplifier (OTA) includes a first, a second and a third differential units, a voltage-to-current converting unit and a current subtraction device. The first and the second differential units receive a differential input voltage and the voltage-to-current converting unit converts it into an output current. The OTA adopts a replica scheme, that is, by copying the first differential unit to generate a third differential unit and then performs a subtraction between the first output current from the first differential unit and the second output current from the third differential unit in order to eliminate the static current component in the output current. In addition, since the first and the third differential units have the same layout, the output current will not vary with the channel length modulation of transistors, and the static current component in the output current can be eliminated completely.

Abstract: A complementary transconductance amplifier having a common mode feedback circuit includes a first-type transconductor, a second-type transconductor and a common mode feedback circuit. The first-type transconductor generates a first differential output signal pair in response to a differential input signal pair under the control of a first control signal. The second-type transconductor generates a second differential output signal pair in response to the differential input signal pair under the control of a second control signal. The common mode feedback circuit generates the second control signal in response to the first and second differential output signal pairs under the control of a common mode control signal.

Abstract: The present invention relates to an input circuit for receiving an input signal in an integrated circuit, having a differential amplifier whose first input can have a predetermined reference voltage applied to it and whose second input can have the input signal applied to it, and having a current source for operating the differential amplifier at its operating point, wherein a setting circuit is connected to the current source in order to set the operating point of the differential amplifier in an optimum manner on the basis of the predetermined reference voltage.

Abstract: A variable-gain amplifier has distortion characteristics (IIP3) improved when the gain is attenuated without impairing characteristics with respect to a gain PG and a noise figure NF when the gain is maximum. The variable-gain amplifier has a plurality of parallel-connected dual-gate FETs having first FETs (6), (8) having gates for being supplied with an input signal and second FETs (7), (9) connected in cascade to the first FETs (6), (8), respectively. Gate control voltages (Vcon1, Vcon2) can separately be applied to the second FETs (7), (9), respectively, from voltage control means.

Abstract: An amplifier 11 to which transistors 13 and 14 functioning as variable resistors are connected in parallel is used. A burst signal is received by a light receiving element 10 and the received signal is converted into an input current signal Iin. The input current signal Iin is converted in the amplifier 11 into an output voltage Vo. Determination is made in a determining circuit 20 as to whether the output voltage Vo exceeds a current voltage V1 which is a threshold. The result of determination is stored in a register circuit 15. Based on the result of determination outputted from the register circuit 15, a desired voltage is selected from among a number of voltages generated beforehand in a control voltage generating circuit. The selected voltage is used to generate a control voltage Vg1 or Vg2 to be applied to the transistors 13 and 14; and the generated control voltage Vg1 or Vg2 is inputted to the transistor 13 or 14 of the amplifier 11.

Abstract: Provided is a low noise amplifier with a common source and a source degeneration, which has linearity, power gain, noise factor, and lossless input matching. The low noise amplifier includes: a first inductor having one terminal connected to an input terminal receiving a signal; a second inductor having one terminal connected to a ground; a MOS transistor having a gate connected to the first inductor, a source connected to the other terminal of the second inductor, and a drain transmitting a signal; and a variable capacitor connected between the source and gate of the MOS transistor and varying an input matching frequency at the input terminal.