Abstract: Transimpedance amplifiers with improved gain-bandwidth products. The transimpedance amplifiers include a boost current circuit to increase the gain-bandwidth product of the transimpedance device, particularly useful when using low voltage power supplies. The boost current can be made responsive to the input current of the amplifier, better accommodating large input currents. The boost current may also be responsive to the power supply voltage, reducing the boost current with increasing power supply voltage. Various embodiments are disclosed.

Abstract: A pre-amp circuit including a photodiode, first and second amplifiers and a differential amplifier reduces or eliminates noise in an input signal. The photodiode converts an external optical signal into an electrical signal which includes noise. The first amplifier amplifies the difference between an output voltage of the photodiode, including the noise, and the reference voltage, to generate a difference signal which includes a first noise component. The second amplifier buffers the reference voltage to generate a signal which includes a second noise component which is in-phase with the first noise component. The differential amplifier amplifies the difference between the voltages output from the first and second amplifiers to generate an output signal which is substantially devoid of such noise. The present invention is amenable to application in remote control receiver systems.

Abstract: A transimpedance amplifier in an optical communication system is provided with automatic gain control (AGC) for increasing the input operating range while maintaining high stability. A photodetector is used to convert an optical signal into a differential current for the transimpedance amplifier. An AGC circuit has a gain control device connected across the differential input of the transimpedance amplifier. The gain control device has an impedance that varies as a function of a voltage at the differential output of the transimpedance. Preferably, the gain control device is a FET having a drain coupled to one of the differential inputs, a source coupled to the other differential input, and a gate for receiving an AGC voltage, the AGC voltage being a function of the voltage at the differential output.

Abstract: An inverting amplification circuit and a feedback resistor are connected in parallel with each other between an input terminal and an output terminal, so that an input current flowing from a photodiode can be converted into an output voltage. Furthermore, a shunt transistor is disposed with its source connected with the input terminal, its gate connected with the output terminal and its drain connected with a ground power supply. When the input current is large, a current flowing into the feedback resistor is decreased, so that a part of the input current can be shunted by the shunt transistor in accordance with a voltage difference between the input terminal and the output terminal. Thus, the output voltage waveform can be free from ringing.

Abstract: A receiver includes a first amplifying circuit for amplifying an input signal to thereby output an amplified input signal. A reference voltage generating circuit has the same configuration as the first amplifying circuit and generates a reference signal having a reference voltage for the amplified input signal. A variable-gain amplifying circuit variably adjusts the gain of the level of a signal derived from the amplified input signal and reference signal. The variable-gain amplifying circuit includes a second amplifying circuit for amplifying the amplified input signal and reference signal for maintaining linearity to thereby output a pair of first differential signals and a pair of second differential signals having shifted levels. A first differential amplifier performs differential amplification based on the first differential signals. A second differential amplifier performs differential amplification based on the first differential signals with a higher gain than the first differential amplifier.

Abstract: A balanced photoreceiver which includes one or more photodiodes coupled to an amplifier that includes a common base configured input stage which operates over a frequency band from DC to millimeter wave frequencies. In one embodiment of the invention, the amplifier is formed as a three-stage direct coupled amplifier which includes a direct coupled complementary common base configured input stage, a complementary common emitter configured Darlington pair intermediate stage and a complementary common collector configured output stage. The common collector configured output stage is used to recombine the complementary current outputs from the input and intermediate stages. The photoreceiver in accordance with the present invention provides relatively superior output waveform symmetry over an increasing power input.

Abstract: The present invention aims to avoid mutual interference of outputs of passive infrared detectors in an amplifier circuit of an infrared sensor to be amplified by a single system of amplifier circuit by cyclically switching outputs from a plurality of passive infrared detectors at a predetermined cycle. P.sub.1 and P.sub.2 each represents a passive infrared detector, and switches 2.sub.1 and 2.sub.2 can be switched over cyclically. Between an operational amplifier 12 and an operational amplifier 13, series circuits of capacitors and switches are provided in parallel as many as the passive infrared detectors. Switches 20.sub.1 and 20.sub.2 are opened and closed in synchronization with the switches 2.sub.1 and 2.sub.2 respectively. The capacitor C.sub.30 is used when an output from the passive infrared detector P.sub.1 is amplified, and a capacitor C.sub.31 is used when an output from the passive infrared detector P.sub.2 is amplified.

Abstract: An optical receiver preamplifier provides a transimpedance feedback path between the output node and the input node that comprises a feedback resister and the two diodes are coupled ("paralleled") in opposite direction. While the input current signal is too large, and the voltage reach the diode's threshold voltage. The preamplifier can provide current path passing the signal to solve the problem that charge-discharge time is not uniform and changed over duty-cycle. Further, the two diodes are coupled ("paralleled") in opposite direction make photo-diode working under the large-signal current by anode or cathode input. Thus, increase the dynamic range of the transimpedance preamplifier. Besides, the low impedance of series resistance connects with input node and feedback network. The influence of bandwidth and stability that the aforementioned two paralleled diodes resulted in diode junction capacitor will reduce due to the low impedance of series resistance.

Abstract: A capacitive transducer which converts impulses of absorbed energy into impulses of electronic charge, combined with a unity-gain, non-inverting amplifier and an integrating capacitor which is substantially smaller than the transducer capacitance, further combined with a transconductance amplifier, comprises a simple and compact radiation detector probe. The detector probe, connected to a signal-receiving assembly through a shielded cable, comprises a useful apparatus for detecting and amplifying weak impulses of energy absorbed from X-ray photons, gamma-ray photons, or nuclear charged particles.

Abstract: A transimpedance amplifier according to the present invention is designed for high-speed fiber optic communications. The transimpedance amplifier preferably includes an input stage, a second stage and a bias generator. The input stage is operably coupled to the second stage and has an input impedance. The second stage has an output impedance. The bias generator is operably coupled to the input stage and the second stage, and operates to bias the input stage and second stage such that the input impedance substantially matches the output impedance. In this manner, the input and output impedances of a transimpedance amplifier of a fiber optics communication receiver are controllable to a desired impedance for interfacing with a transmission line.

Abstract: Output current of light receiving element Dph is converted into a voltage by a core amplification section, and the voltage output is extracted as an amplification output through an outputting circuit section. The output voltage is fed back to the base of transistor T2 of a differential circuit of the core amplification section, by which it is compared with base reference voltage Vref of transistor T1. When the input current is low, the gain of the core amplification section is dominated by the product of the current flowing through transistor T2 and resistor R4, but when the input current is high, the gain is dominated by the product of current flowing through transistor T1 and resistor R3. Consequently, if resistor R3 is set lower than resistor R4, then when the input current is high, the gain margin indicating a degree of stability of the feedback circuit can be made large, and this stabilizes operation of the front-end amplification circuit.

Abstract: A photoelectric cell having a receiving section fitted with an amplifier processing circuit for making the cell immune to electrical disturbances. The processing circuit uses a transfer impedance amplifier A having a gain loop 24 which is shunted by a short-circuit path 24A including a switch T1 controlled by the transmission signal E1. The switch T1 conducts when no pulses are delivered from the transmission signal E1 and does not conduct when pulses are received from the transmission signal E1.

Abstract: The input of a source-follower, or equivalent amplifier sub-circuit, utilizing a low-transconductance, low-reverse-leakage, low-capacitance, junction field-effect transistor, with its gate-source junction forward biased, is directly connected to the input of a charge-integrating preamplifier. This provides an attractive alternative to a high-ohm resistor which is typically used as a discharge element in low-noise charge-integrating preamplifiers in nuclear-particle, x-ray, and gamma-ray spectroscopy.

Abstract: Outputs from an array of input signals are amplified by an amplification section, sampled and multiplexed onto an analog bus. Amplifiers in the amplification section are segregated into groups. When the amplifiers are in a first mode, as indicated by a binning signal, the amplifiers within each group are electrically isolated from another and function independently from one another to provide a high resolution output signal. When in a second mode, amplifiers within a group operate as a single unified amplifier that averages the inputs for that group to provide a single output. Thus, in this second mode of operation, readout speed may be improved while increasing the signal-to-noise ratio of each input signal relative to the first mode of operation.

Abstract: An apparatus for providing a varying impedance point in a circuit corresponding to a frequency of an input signal applied to the apparatus. Device sizes of the apparatus can be selected to provide varying impedance for desired frequency ranges.

Abstract: A low noise, high gain-bandwidth preamplifier is formed which employs positive, capacitive feedback to compensate the frequency response of the amplifier for an applied input capacitance. The circuit includes a differential amplifier circuit with conventional resistive, negative feedback. The circuit further includes a pair of compensating capacitors coupled across the amplifier, providing positive feedback which compensates for an applied input capacitance. The preamplifier circuit provides a high gain-bandwidth along with enhanced noise performance.

Abstract: A low noise transistor IC or module comprises a plurality of conventional CMOS transistors which are laid out in parallel in such a way that the effective gate width of the combination of transistors is increased, yet the effective gate resistance and hence the noise figure (NF) of the circuit are reduced. A low noise amplifier incorporating such a module is also described.

Abstract: An amplifier circuit unit is composed of an offset compensation circuit for equalizing and issuing a DC potential in data input period of one input signal of differential input signals, and a DC potential in data input period of other input signal, and an amplitude limiting amplifier circuit for receiving a differential output signal from this offset compensation circuit as an input signal, and issuing to a differential output terminal as a differential output signal kept in a constant output signal amplitude while amplifying in a linear region. This amplifier circuit unit is connected in cascade in plural stages as required, and is applied to an amplifier circuit of an optical receiving circuit and others.

Abstract: A feedback amplifier includes an input terminal where an input voltage is detected from an input current; an amplifier circuit which amplifies the input voltage to generate an output signal; a first output terminal from which the output signal is outputted; and a feedback circuit. The feedback circuit includes a feedback resistor connected between the input terminal and the first output terminal; and a diode which connected in parallel to the feedback resistor. The output signal is feedback-controlled in response to the product of the input current and the impedance of the feedback circuit.

Abstract: When a third transistor receives first photoelectric currents outputted from a sensing photodiode, the third transistor provides second photoelectric currents to bases of a first transistor and a second transistor, then the first transistor turns on and carries the first photoelectric currents, so first currents corresponding to the first photoelectric currents flow to a first terminal. Thus, the first photoelectric currents can be directly outputted from the first terminal. On the other hand, the second transistor also turns on and carries second currents corresponding to amplified first photoelectric currents, so the second currents flow to a third terminal. Thus, the amplified first photoelectric currents can be outputted from the third terminal.

Abstract: An automatic threshold control circuit includes a bottom detection circuit, a relative peak detection circuit, and a voltage divider circuit. The bottom detection circuit detects an absolute minimum level of an input signal, and the relative peak detection circuit detects, in accordance with the input signal, a maximum level relative to the minimum level detected by the absolute bottom detection circuit. Further, the voltage divider circuit generates a threshold level by dividing the absolute minimum level and the relative maximum level in a predetermined ratio. Using this configuration, a signal amplifying circuit can be constructed that is capable of accurately reproducing digital signals at all times regardless of variations in the amplitude or the DC level of the input signal.

Abstract: In an optical receiver including an avalanche photodiode (APD), a monitor circuit monitors the operating point of a preamplifier. A bias control circuit usually transfers a control signal received from an AGC (Automatic Gain Control) control circuit to an APD bias circuit. When the value being monitored by the monitor circuit exceeds a preselected level, the bias control circuit controls the APD bias circuit such that the above value coincides with the preselected level. The various sections of the receiver are free from damage ascribable to an increase in the photocurrent of the APD.

Abstract: A broad-band amplifier circuit is furnished with a plurality of amplifiers with a coupling capacitor being interposed between every two adjacent amplifiers. Each coupling capacitor has a capacity large enough to prevent adverse effect of external noise. Accordingly, not only the passing of a signal having a low frequency is allowed, but also an element operable in a high frequency, such as a Schottky transistor, can be provided in each amplifier as a transistor. At least the transistor of the amplifier in the last stage is connected to a diode, so that the charges accumulated between its collector and base while the amplifier stays on are fed back and eliminated. Accordingly, the broad-band amplifier circuit can carry out a flat amplifying operation over a wide range from low to high frequency bands, and therefore, can be used for all the ASK method, IrDA1.0 method, and IrDA1.1 method. Consequently, not only the manufacturing cost, but also the size of the broad-band amplifier circuit can be reduced.

Abstract: An imaging device of the present invention comprises driver transistors 23.sub.1 through 23.sub.n and load transistors 24.sub.1 through 24.sub.n. The imaging device has a switch switching output of the driver transistor 23n-1 to output terminal Vout 2 or to the driver transistor 23n as an output signal.

Abstract: An optical signal is converted by a light-receiving element into a photoelectric current. The photoelectric current is converted by a preamplifier into a positive phase voltage and the opposite phase voltage. The peaks of the positive phase output and opposite phase output are sensed and held by a first and second peak sensing circuits. The median between the output of the second peak sensing circuit and the positive phase output of the preamplifier is determined by a first median output circuit. The median between the output of the first peak sensing circuit and the opposite phase output of the preamplifier is determined by a second median output circuit. A level comparison circuit compares the outputs of the first and second median output circuits and produces a signal voltage with a constant amplitude within a specific input voltage range, thereby producing a reception signal.

Abstract: An automatic output offset control circuit for a DC-coupled RF amplified optical-to-electrical converter has a photodiode for converting an optical signal to an electrical signal. The current from one side of the photodiode is coupled into the input of a bipolar RF amplifier that generates a voltage output. The current from the other side of the photodiode is sensed for generating a voltage that is compared with the output of the RF amplifier. Any mismatch between the sensed current and the RF amplifier generates an error signal that is used to control the DC bias supplies of the RF amplifier. The DC bias supplies are adjusted in unison to produce the correct offset at the amplifier output for the given photodiode current while maintaining a constant AC-gain. The circuit automatically corrects for the DC-coupled output offset drift and variations of the RF bipolar amplifier. The circuit may be implemented using either voltage or current signals to the feedback circuit.

Abstract: A differential amplifier receiving a first input signal and a second input signal, respectively, and amplifying voltage difference between the first and second input signals to output an output signal includes a first source follower circuit receiving an external data signal as the first input signal, and having an output node; a second source following circuit having a constant current source FET and receiving a reference voltage as the second input signal; and a bias circuit providing a signal having the same phase as the data signal from the output node of the first source follower circuit and inputting that signal to a gate terminal of the constant current source FET of the second source follower circuit.

Abstract: An amplifier circuit includes an amplifier which derives an output voltage from an input current, and a bypass circuit which bypasses part of the input current so that the remainder of the input current is applied to the amplifier.

Abstract: The current output amplifier for a charge coupled device includes: a charge detection node 56; a first transistor 52 having a gate coupled to the charge detection node 56; a second transistor 50 having a gate coupled to a source of the first transistor 52 and a drain coupled to an output node 62; and a constant current source 60 coupled to the drain of the second transistor 50.

Abstract: A current amplifier includes a cascode transistor for fixing the voltage of an input of the amplifier; a first constant current source connected between the input and a first supply voltage; a second constant current source, for providing a current lower than the first current source, connected between a second supply voltage and the cascode transistor; a second transistor, of different type than the cascode transistor, connected between the input and the second supply voltage, and controlled by the node between the cascode transistor and the second current source; and an output transistor of same type as the second transistor, connected to the second supply voltage and controlled by the node.

Abstract: A continuously tunable wideband optical communications receiver exhibits optimum performance across multiple octaves of received signal bandwidth. The receiver's transimpedance preamplifier input stage includes a variable transconductance field effect transistor, whose transconductance exhibits a very steep non-linear variation with drain current over the operational bandwidth of the transimpedance amplifier. As a result, the bandwidth of the transimpedance amplifier and therefore the receiver can be tuned to accommodate the detected data rate. The data rate of the received signal (known either a priori, or extracted by a clock recovery circuit) is used to adjust drain current and thereby tune the operational bandwidth of the receiver.

Abstract: A pre-amplifier disclosed in which low noise at the time of small input and linear amplification at the time of large input are compatible. In a pre-amplifier, such compatibility can be realized by constituting a current mirror circuit, with respect to a current of a first stage transistor in a transimpedance portion, by a by-passing transistor which is provided at an input side of the pre-amplifier. In such a configuration, by making a by-pass current flow proportionally to an input instantaneous current at the time of a large input, the transimpedance can be made small equivalently to thereby widen the dynamic range.

Abstract: A voltage isolation circuit having an improved method of combining the HF path and LF path is provided. The LF path comprises an opto-isolator to achieve voltage isolation of the input signal while passing low frequencies. The HF path comprises a transformer to achieve voltage isolation of the input signal while passing high frequencies. The HF path and LF path are combined at a summing node to obtain an isolated input signal. Obtaining a flat frequency response requires that the cross-over frequency between the LF path and HF path be closely matched. A portion of the LF path is injected into the HF path such that LF components are canceled out in the region of the transition frequency. In this way, the pole frequency of the transformer in the HF path may be compensated for to achieve a flat frequency response for the combined LF and HF paths.

Abstract: A negative feedback preamplifier having variable conversion gain control and variable open loop gain control capabilities which can work correctly regardless of semiconductor process variations. The negative feedback preamplifier used to convert an input signal current to a signal in the form of voltage includes: a resistor which determines the current-voltage conversion gain when a small signal current is input to the negative feedback preamplifier; a diode which switches the current-voltage conversion gain when a large signal current is input to the negative feedback preamplifier; a resistor which determines the current-voltage conversion gain when the large signal current is input; a grounded source amplifier including a main FET which is biased such that its transconductance decreases when the large signal current is input; and a bias setting portion (diode) which determines the bias condition associated with the main FET.

Abstract: An amplifier section is supplied with an electric signal outputted from a light-sensitive detector. The amplifier section comprises an amplifying circuit for amplifying the electric signal into an amplified signal having an amplified level. A producing section produces a control signal on the basis of the amplified signal and a reference voltage. A resistor section is connected to the amplifying circuit in parallel. The resistor section has a variable resistance which is varied in accordance with the control signal. A capacitor section has a capacitor and connects the input of the amplifying circuit and the output of the amplifying circuit through the capacitor in response to the control signal.

Abstract: The photocurrent generated by a photodiode receiving light substantially flows through a feedback resistor when the incident light intensity is low. As the incident light intensity increases, the source and drain of a FET connected in parallel to the feedback resistor establish a conducting state therebetween, whereby the photocurrent is divided into a current flowing through the feedback resistor and a current flowing through the FET connected in parallel to the feedback resistor. Accordingly, transimpedance is equivalently lowered, while the feedback resistor is restrained from lowering the output potential. When the incident light intensity is further increased, a gate bias current flows into the gate of an input-stage FET of an amplifier, whereby the photocurrent is divided into the current flowing through the feedback resistor, the current flowing through the FET connected in parallel to the feedback resistor, and the gate bias current.

Abstract: In a preamplifier for amplifying an input signal supplied to an input terminal to supply an amplified output signal and a reference output signal to an output terminal and a reference output terminal, respectively, a reference level circuit produces a reference level. An amplifier is connected to the reference level circuit and has a predetermined structure. The amplifier amplifies the input signal into the amplified output signal with reference to the reference level to supply the amplified output signal to the output terminal. A dummy circuit is connected to the reference level circuit and has a structure which is identical with the predetermined structure. The dummy circuit responds to the reference level to produce the reference output signal related to the amplified output signal.

Abstract: A method and apparatus for receiving infrared signals are provided. The circuit includes preamplifier that includes an integrator that charges based on light detected by a photodiode. The circuit includes a warning circuit that generates a warning flag when the charge on the integrator exceeds a predetermined level. To prevent the integrator from saturation, digital logic resets the preamplifier by dumping the charge on the integrator in response to the warning signal. The digital logic is also configured to reset the integrator at predetermined intervals. When the incoming signal is encoded using pulse position modulation, the interval at which the integrator is reset is the length of a single time slot in the pulse position modulation frame. A sample and hold circuit is provided to hold a previous output of the preamplifier. The difference between the previous output of the preamplifier and the current output of the preamplifier is compared with a threshold voltage to detect pulses on the incoming signal.

Abstract: An amplifier circuit (1) is arranged to amplify a signal of variable magnitude from a photodiode (3) having capacitive characteristics. The circuit (1) comprises a first feedback path containing a voltage controlled variable resistor (8) for varying the gain of the amplifier in relation to the magnitude of the signal so as to provide an output signal of substantially uniform magnitude. The first feedback path also contains a capacitor (7) which compensates for adverse effects of reactance in the circuit caused by the capacitance of the photodiode (3) and of the variable resistor (8) in order to optimize the frequency response characteristics of the amplifier. A second feedback path comprising a fixed value resistor (9) becomes operable when the resistance of the first feedback path is large to provide fixed gain amplification of signals received from the photodiode (3).

Abstract: The semiconductor amplifier circuit provided with frequency characteristics excellent in both band width and flatness is disclosed. The amplifier circuit comprises: an input section (10) including: a first inversion amplifier circuit (11) for inversion-amplifying an input signal; and a feedback circuit (15) of a field effect transistor having a grounded gate, a source for receiving a feedback signal, and a drain connected to an output terminal of the first inversion amplifier circuit; a first level shift circuit (20) for shifting level of an output of the input section; a second inversion amplifier circuit (30) for inversion-amplifying an output of the first level shift circuit; and a second level shift circuit (40) for shifting level of an output of the second inversion amplifier circuit. Here, the amplifier circuit is characterized in that the output of the second level shift circuit (40) is applied to the feedback circuit (15) as the feedback signal.

Abstract: A highly sensitive optical receiver where one terminal of the photodiode of the receiver is connected to a negatively biased amplifier while the other terminal of photodetector is connected to a positively biased amplifier, where such connections automatically bias the photodiode and use the current from both terminals (anode and cathode) of the photodiode. This invention also provides an optical receiver which has a DC cancellation circuit to eliminate the biasing voltages in the final output signal.

Abstract: A preamplifier overload control circuit which enhances the dynamic range of the preamplifier. Separate paths shunt corresponding DC and AC components of the signal from an electro-optical device away from the preamplifier input. The amount of shunting in both paths are controlled by a common control signal, here the average DC value of the signal, such that substantially all of the DC signal is shunted away from the preamplifier input.

Abstract: A transimpedance amplifier (10, 50) is provided for processing a current signal received from a circuit device (12, 52). The circuit device (12, 52) can be a photodiode used to receive infrared transmissions. The transimpedance amplifier (10, 50) includes a first stage (14, 54) coupled to an input node. The first stage (14, 54) has a first amplifier (20, 60) operable to drive the input node and is operable to provide a current signal to a second node (NODE 3, NODE 2) in response to a current signal in the input node. A second stage (16, 56) is connected to the second node (NODE 3, NODE 2). The second stage (16, 56) has a second amplifier (32, 68) and is operable to convert the current signal in the second node (NODE 3, NODE 2) into an output voltage signal (V.sub.OUT) at an output node. A feedback loop (18, 58) can be connected to receive the output voltage signal (V.sub.OUT) and to provide a feedback current signal to cancel ambient noise in the current signal in the input node.

Abstract: A limiting transimpedance amplifier includes an amplifier stage including a feedback resistor, a limiting diode coupled across the feedback resistor, and a stabilization diode coupled to the amplifier stage to compensate for feedback instability introduced by the limiting diode. The amplifier stage includes an input transistor and an output transistor, where the feedback resistor couples an output of the output transistor to an input of an input transistor. A stabilization voltage generator is coupled to the stabilization diode to provide a stabilization voltage that causes the desired compensation.

Abstract: A transconductance device particularly suitable for use as a high frequency active filter has an input stage including at least one field effect transistor (M.sub.1) arranged to drive a laser diode (LD.sub.1) and an output stage including at least one photodiode (PD.sub.1) optically coupled to the laser diode. The output stage is preferably provided with a high impedance bias current supply circuit. In an alternative arrangement particularly useful as an operational amplifier, a differential input stage includes a pair of laser diodes (LD.sub.1 and LD.sub.2) optically coupled to respective photodiodes (PD.sub.1 and PD.sub.2) connected in series, the output being taken from the junction of the two photodiodes.

Abstract: Automatic Gain Transimpedance Amplifiers for analog applications having high bandwidth, wide dynamic range, and ultra-high linearity. The transimpedance amplifiers includes an operational amplifier and a variable feedback resistance means connected between the input and the output of the amplifier. The variable feedback resistance means may include a single feedback PIN diode, two serially connected feedback PIN didoes, a PIN diode connected to a feedback resistor in parallel, or two serially connected PIN diodes connected to a feedback resistor in parallel. Ultra-high linearity is achieved because the dynamic resistance of the PIN diode under forward bias is substantially linearly dependent on the inverse of the current that passes the diode.

Abstract: A transimpedance amplifier circuit includes an inverting voltage amplifier having an input being supplied with an input current and an output carrying an output voltage. A coupling member is connected between the input and the output of the voltage amplifier. The coupling member has two diodes being connected antiserially to one another between the input and the output of the voltage amplifier with a common node point. A transistor has a load path being connected between the common node point and a ground potential. A differential amplifier has one input connected to the input of the voltage amplifier, another input connected to the output of the voltage amplifier, and an output. A low-pass filter is connected downstream of the differential amplifier for furnishing a trigger signal at the output to the transistor.

Abstract: A transimpedance amplifier has an amplifier unit, a feedback resistor arranged between the output and input ends of the amplifier unit, a voltage clamp unit connected to the opposite ends of the feedback resistor, to clamp a voltage applied to the ends of the feedback resistor and prevent the amplifier unit from saturating, a current absorption unit arranged on the input side of the amplifier unit, to absorb any large input current supplied to the amplifier unit, and a switching selection unit to activate or deactivate the current absorption unit according to an external control signal. The current absorption unit is activated through the switching selection unit when a large input current is produced to write data to a magneto-optic disk in a magneto-optic disk unit in which the transimpedance amplifier is installed.

Abstract: A Compressing Capacitively Coupled Transimpedance Amplifier (CCTIA) circuit (10) has an amplifier (AMP) with a variable capacitance feedback network (C1, C2, C3, Q1, Q2) coupled between a current receiving amplifier input node and an amplifier output node. The output node outputs a voltage in response to a received current. The variable capacitance feedback network is responsive to the output voltage for establishing one of a plurality of different transimpedance values for the circuit such that the circuit exhibits a greatest transimpedance value for an input current having a magnitude below a threshold magnitude, and a lesser transimpedance value for an input current having a magnitude equal to or above the threshold magnitude.

Abstract: An integrated circuit photodetector includes a transimpedance amplifier including a differential amplifier stage with PNP emitter-coupled transistors and a PNP input transistor which are biased only by base currents of the emitter-coupled transistors, to achieve low input bias current. Low noise operation is achieved by bypass capacitors coupled between the bases and emitters of the input transistors, respectively. A constant current source supplies a current which develops a small pedestal voltage across a resistor to bias the non-inverting input of the transimpedance amplifier so as to avoid nonlinear amplification of low level light signals. A positively biased N-type guard tub surrounds the photodetector, which is formed in a junction-isolated N region on a P substrate, to collect electrons generated in the substrate by deep-penetrating IR light to prevent them from causing amplification errors.