Showing papers on "Output impedance published in 1985"

Modelling frequency dependence of output impedance of a microwave MESFET at low frequencies

Abstract: Measurements showing the frequency dependence of MESFET drain impedance at low frequencies have been performed. A simple model which simulates this behaviour is also proposed.

CMOS voltage references using lateral bipolar transistors

Abstract: Two bandgap references are presented which make use of CMOS compatible lateral bipolar transistors. The circuits are designed to be insensitive to the low beta and alpha current gains of these devices. Their accuracy is not degraded by any amplifier offset. The first reference has an intrinsic low output impedance. Experimental results yield an output voltage which is constant within 2 mV, over the commercial temperature range (0 to 70/spl deg/C), when all the circuits of the same batch are trimmed at a single temperature. The load regulation is 3.5 /spl mu/V//spl mu/A, and the power supply rejection ratio (PSRR) at 100 Hz is 60 dB. Measurements on a second reference yield a PSRR of minimum 77 dB at 100 Hz. Temperature behaviour is identical to the first circuit presented. This circuit requires a supply voltage of only 1.7 V.

Impedance of the Residential Power-Distribution Circuit

Abstract: This paper presents measurements and analysis of the impedance of residential power-distribution circuits at frequencies from 5 to 20 kHz. These frequencies are used by systems such as distribution-line carriers which use the power distribution circuit as a communications medium. Residential impedances are determined by the distribution transformer secondary windings, entrance cables, house wiring, and electrical loads. Impedance measurements of these components and measurements at four residences are presented.

Low power cmos reference generator with low impedance driver

Abstract: A low power, low output impedance, CMOS voltage reference with high source/sink current driving capability. A CMOS current mirror preamplifier includes matched transistor pairs having their W/L ratios scaled to reduce the level of current to the subthreshold region. A CMOS source follower output stage also has its transistors biased in the subthreshold region. Circuitry for protecting the preamplifier from the effects of supply voltage and output voltage bumps is also disclosed.

Low power line driving digital transmission system

Abstract: @ A low power line driving transmission apparatus is described in which TDM signals are transmitted between points over a transmission line comprising a pair of conductors and in which the characteristic impedance of the transmission line and the source impedance of the transmitters is matched and wherein the input impedance of the receivers is sufficiently high to present an effective open circuit to received signals. Under these conditions the transmitter dissipates power only during logical transitions of the input signals.

FET output drive circuit with parasitic transistor inhibition

Abstract: A CMOS output drive circuit has two field effect transistors (FETs) implemented with a CMOS process and characterized by parasitic bipolar transistors. The back-gates of the two transistors are tied together, such as by forming the devices in a common well, and the back-gate of the second FET is also connected to prevent its associated parasitic bipolar transistor from conducting. Quiescent loads are applied to the two FETs so that their voltages are comparable during low output loading, resulting in a drive circuit with high input impedance and high output voltage swing. The output terminal is taken from the first FET, the voltage of which becomes unbalanced from the second FET at relatively high output loads, turning on the parasitic bipolar transistor for the first FET. This gives the drive circuit a desirably high input impedance and low output impedance for heavy output loads. The circuit thus sacrifices low output impedance for high input impedance and voltage swing during light output loading when output impedance is not very important, and sacrifices high voltage swing for high input impedance and low output impedance at heavy loads at which the impedance levels are more important than voltage swing.

Impedance mismatch detector

Abstract: A mismatch detector is provided for determining whether or not a particular load impedance is matched or mismatched to the characteristic impedance of a transmission line. The detector is capable of determining if a particular load impedance has a value outside of an impedance threshold circle having a center at a location other than at the center of the Smith Chart. This flexibility enables the detector to be more selective in determining improper load conditions.

Two quadrant power modulator

Abstract: A two quadrant power modulator using bi-directional and uni-directional flyback converters in which output waveshape is determined by the modulation of the pulse repetition rate and width. The output voltage is equal to the square root of the driving function. A large number of converters may be paralleled with sequential switching to raise the output power and raise the output ripple frequency, thereby simplifying filtering. Output voltage is constant with varying load condition irrespective of the reactive or non-linear nature of the load. A two quadrant power modulator using flyback converters to generate a time varying voltage. Dynamic regulation and low output impedance are achieved without use of closed loop control. Input voltage is not distorted by reactive and/or non-linear loads.

Complex conductivity measurements between 26 and 110 GHz using complex impedance bridges

Abstract: A method is described of measuring complex conductivity based upon the measurement of the impedance of a sample placed in a waveguide using a complex impedance bridge. From the observed changes in the bridge parameters, viz., attenuation and phase shift, the impedance and, hence, the complex conductivity are inferred. The principles and details of operation of three bridges covering the frequency range 26 to 110 GHz are discussed. The measurement technique was verified for lossless samples and for lossy resistive wires. An example of temperature and frequency dependent complex conductivity measurements on a linear chain material is presented.

High to low transition speed up circuit for TTL-type gates

Abstract: The specification discloses an input transistor (14) which is variable between high and low impedance states in response to input voltage transitions at terminal 10. An output transistor (16) is coupled to the input transistor (14) and is responsive to an input transition at terminal 10 for changing impedance states. Circuitry including a speed up transistor (44) is coupled between the input transistor (14) and output transistor (16) for applying added current to the output transistor (16) to speed the change of impedance state. The circuitry applies added current to output transistor (16) until the output voltage at terminal (18) falls below twice the base-emitter voltage of the output transistor (16).

Output waveform improving method of inverter

Abstract: PURPOSE:To improve the output voltage distortion of an inverter due to a nonlinear load by multiplying an output impedance by harmonic waves of the respective orders obtained from an output current, and superposing a voltage produced by combining them on the output voltage of the inverter. CONSTITUTION:The output of an inverter 1 is supplied through a reactor 2 and a capacitor 3 to a nonlinear load 4 made of a rectifier. A current transformer 9 detects the output current of the inverter 1, and the detected current is supplied to harmonic filters 10 of the respective orders. The harmonic components obtained here are inputted to an output impedance multiplier 11 of the inverter, which multiplies and combines the harmonic components and the output impedance value. The combined output is superposed on the output voltage of the inverter 1, and the harmonic components of the voltage are compensated by the voltages.

Zero standby current switch method and apparatus

Abstract: A bipolar switch is disclosed having a near zero standby current characteristic, low output impedance in the "on" state, and near infinite impedance in the "off" state. The switch is responsive to a control signal to apply regulated power to a load. The switch includes a turn-on detect circuit which is powered solely from the control signal, and switching circuitry which is powered from a power source but which normally draws no standby current when the switch is in its "off" state. The switching circuitry includes speed-up circuitry to permit rapid turn-on, circuitry which employs positive feedback to achieve high current gain, and circuitry for rapidly turning off the switch.

Electronic hybrid circuit

Abstract: An electronic hybrid circuit includes a differential amplifier having its non-inverting input coupled via a resistor to a four-wire input port and via a coupling transformer to a two-wire input/output port, its output coupled to a four-wire output port, and its inverting input coupled via a resistor to the input port and also coupled to an impedance network. The impedance network includes an inductive impedance which is coupled either to the amplifier output or to circuit ground, and which may be constituted by a gyrator or other electronic circuit which simulates an inductor.

Battery state detector

Abstract: PURPOSE:To enable the detection of the state of a battery by determining the residual capacity and residual life of the battery from the output thereof and the output impedance. CONSTITUTION:A data table into which the residual capacity and the residual life data of a battery 15 is registered corresponding to the input/output impedance is inputted into a memory 13 beforehand. A charger 18 and a load device 17 are turned OFF with a microcomputer 11 to measure leakage current flowing into a battery 15 and the terminal voltage. Then, after the load device 17 is OFF while the charger 18 ON, the inflow current to the battery 15 and the charged voltage thereof are measured and the input impedance of the battery 15 is obtained by a specified formula. Then, after the load device 17 is OFF and the charger 18 OFF, the leakage current to a circuit from the battery 15 and the terminal voltage are measured. After the charger 18 is OFF while the load device 17 ON, the outflow current from the battery 15 and the load voltage are measured and the output impedance of the battery 15 is obtained by the specified formula. The data table is retrieved in the memory 13 from the input and output impedances to determine and display 23 the residual capacity and the residual life of the battery 15.

High output programmable signal current source for low output impedance applications

Abstract: The present invention relates to a high output programmable current source.omplementary output stages are connected between appropriate power supply polarities for driving a low impedance load which is connected to circuit ground. An operational amplifier is connected between the input and emitter of each of the complementary stages providing negative feedback for virtually eliminating the input offset voltage of the respective output stage. A programmable function signal source is connected to the operational amplifiers for driving a programmable signal current to the extent possible through the load resistance from a limited voltage supply.

A Five-Part Resistor-Capacitor Network for Measurement of Voltage and Current Levels Related To Electric Shock and Burns

Abstract: This paper discusses the development of a five-part equivalent body impedance and reaction network which can be used to more accurately relate leakage current and voltage measurements to electric shock than do conventional methods. Measurements of body impedance were made on people over a frequency range of 30Hz to 1 MHz, using four methods, to define body impedance values for various conditions of contact. The advantage of the network is that the current in the body impedance section is the actual current which would be expected if a person made the contact, regardless of source impedance, wave shape, frequency, or combination of mixed frequency currents. Calculations of body response to voltage, using the network, show that the frequency of maximum electric shock from voltage contact lies between 500Hz and 3kHz instead of 50 to 60Hz. This effect was verified on several people with an “Involuntary Squeeze Test” which measured the voltage required for muscular contractions of the hand up to 20kHz. The squeeze point is a reference intensity of electric shock near the point of inability to let go. Application of the network to mixed frequencies is discussed, and measurements on people in which 60Hz currents were mixed with currents at frequencies between 30Hz and 100kHz are presented. This data and a comparison of electric shock effects from sine and square waves indicate that the network peak indicated current is the value which most accurately relates to electric shock. Information on leakage current burn related limits and their measurement with the five-part network is also included. The network actual current in mA RMS can be related to electric burns.

Programmable reference voltage generator for a read only memory

Abstract: A read only memory (ROM) includes a series of bit lines biased by a reference voltage lead (102). The reference voltage lead (102) is connected to a first reference voltage generator (100) having an output impedance of 25 ohms and a second reference voltage generator (104) having an output impedance of 75,000 ohms. When the ROM is deselected, the first reference voltage generator (100) turns off and the bit lines are biased by the second reference voltage generator (100). However, when the ROM is selected, the first reference voltage generator (100) is turned on and biases the bit lines. In this way, a ROM is provided which can operate in a low power mode without decreasing the access time when the ROM goes from a deselected state into a selected state.

Battery feed circuit for a pair of subscriber lines

Abstract: Battery feed circuit for a pair of subscriber lines includes a voltage drive circuit with an operational amplifier having a predetermined output impedance determined by an alternating current terminal impedance for the pair of subscriber lines. Both voice signals and induced noise signals are terminated by the voltage drive circuit. The voltage drive circuit is connected in parallel with an electronic inductance circuit, between one of the subscriber lines and ground or a direct current voltage supply.

Pen touch type information input device

Abstract: PURPOSE:To make a signal detecting pen and a cable small-sized, and also to raise an operability of a device by constituting so that a switching signal and a position information detecting signal of a tablet surface are sent to a body from the signal detecting pen by the same common signal line. CONSTITUTION:In case when a signal detecting pen 30 does not abut on a tablet 62 and a detecting rod 39 is reset forward, a pen switch 44 is closed, an impedance of a cable 45 becomes zero, and voltage (v) of a signal line 47 always becomes zero. On the other hand, when the pen 30 abuts on the tablet 62, the switch 44 is opened, the impedance becomes high, and voltage V0 determined by a voltage dividing ratio of resistances R1, R2 is applied to the signal line 47, and v=V0. Accordingly, make and break of the switch 44 can be detected from a voltage variation of the signal line 47. An impedance converting circuit 51 is connected to the signal line 47, and voltage V of the signal line 47 is outputted as it is in a low output impedance state.

Body impedance for transient high voltage currents

Abstract: High voltage, short duration capacitive discharge measurements of human body impedance have been accomplished for different paths through the body. Skin contact impedance and internal body impedance between various locations on the body were examined. Impedance measurement instrumentation capable of measuring impedance once every 0.05 μs was used. Voltages of 100 to 2000 V were applied giving peak currents of 0.2 to 5.0 A. The voltage and current waveforms had time constants ranging from 0.2 to 5.0 μs. These short time constants are consistent with safety requirements, allowing testing with people. However, these impedance measurements can be interpreted as limiting values for shocks of longer, possibly lethal duration. The initial total body impedance between the palm of the hand and the sole of the foot was found to be about 500 to 530 Ω. The internal body impedance for the same current path was found to be about 430 Ω. The internal body impedance between the wrist and the calf was found to be about 50% of the internal body impedance measured between the palm and the sole of the foot.

Method and device for limiting switching-on currents

Abstract: In the case of the method for limiting a switching-on current when a load is being connected to an electrical network, two suitably formed voltages are compared and current pulses are passed to a current gate, which current pulses gradually open said current gate during the switching-on process. In consequence, overcurrents during the switching-on process are prevented, as can occur when the initial internal impedance of the load is still low, as a result of cold incandescent elements and heating wires, when lamps or heating elements are connected to the electrical network. Circuit arrangements for carrying out the method are specified. The method and the circuit arrangement which operates in accordance with the method are particularly suitable for mass production, for domestic use, as a result of the physically small dimensions and the extremely cost-effective production capabilities.

Comparator input stage for interface with signal current

Abstract: A current interface has an impedance buffering circuit which maintains a very low input impedance at an input node, while producing currents to two current outputs which increase and decrease, respectively, with increases and decreases in the input current flow. In a preferred embodiment, the impedance buffering circuit is an operational amplifier which has been modified to provide access to the collector terminals of a complementary output transistor pair. The collector terminals are connected to current mirrors which are also connected to an output node of the interface circuit. The amplifier and current mirrors effectively buffer the input and reconstruct changes in the input current at the output node, while maintaining a very low input impedance at the input node. Compensation for errors introduced by the changes in base currents of the complementary output pair is provided by a matching pair of complementary transistors.

In-Circuit Impedance Measurement Using Current Sensing

Abstract: A novel approach to in-circuit measurement of resistors, capacitors, and inductors was evolved. This approach utilizes current sensing, making possible the measurement of in-circuit components which may be directly shunted by impedances as much as two to three orders of magnitude lower in impedance than the unknown. A minature clip-on probe was developed to facilitate measurements of components mounted on printed circuit boards. A compact impedance comparator was constructed which measured in-circuit components within approximately 2 to 4-percent accuracy over the following ranges: for resistance, 1.5 ? to 1 M?; for capacitance, 100 pF to 60 ?F; and for inductance, 400 ?H to 60 H. Impedances as low as one to three orders of magnitude smaller than the measured element impedance, depending on the probe used, shunted the unknown when the stated accuracy was measured. Much of the quoted inaccuracy is due to the ±3-percent resistance and ±0.1-percent linearity tolerances of the reference resistor which was used for all measurements.

Phase split circuit

Abstract: PURPOSE: To bring a phase difference between two outputted signals to 180° accurately without being immune to a floating capacitance even when a high frequency input signal is given by connecting transistor (TR) having the same characteristic as a TR of a phase split circuit to a feedback circuit in the phase split circuit using the TR outputting two signals (in phase and opposite phase signals) to a given signal. CONSTITUTION: Since a TR Q 2 has the same characteristic as that of a TR Q 1 , the same collector substrate capacitance C cs as that of the TR Q 1 is given to a collector terminal. Thus, the equivalent circuit is shown in figure. In this case, since the emitter output impedance is small, an emitter output signal voltage VE is expressed as VE=Vin. Since a collector output signal voltage V c is expressed as V c =VE because of the capacitance C cs connected in parallel with the feedback circuit of the TR Q 1 being an amplifier, the emitter output signal and the collector output signal become respectively and accurately in- phase and opposite-phase signals with equal amplitude to the input signal. COPYRIGHT: (C)1986,JPO&Japio

Method of testing telephone subscriber's lines

Abstract: To test the attenuation of a telephone subscriber's line two measurements are made with the telephone on hook, one at a relatively low frequency and the other at a relatively high frequency. The frequencies chosen in one case are 900 Hz and 3 KHz. To do this a signal generator (SG) with a known internal impedance, e.g. 600 ohms, is connected to the line wires (LW1 and LW2), and the voltage ratio Vo/Vs determined. The two ratios thus obtained, plus a knowledge of the internal resistance of the generator, give a good assessment of the line's impedance characteristics.

Optical receiver with negative feedback

Abstract: A bootstrap negative feedback type photoelectric converting circuit for converting an optical signal into an electrical signal. A light receiving element receives incident light and provides an electrical signal to a field effect transistor (FET) and an inverting amplifier. A bipolar transistor is directly connected to the FET in complementary fashion to increase the gain of the source-follower amplifier to substantially unity and to reduce its output impedance to a very small value in order to reduce the effects of parasitic capacitance of the light receiving element at high frequencies.

High frequency switching circuit

Abstract: PURPOSE:To improve the reliability and to attan small size and light weight by inserting respectively a switch circuit between each midpoint of two lines having a characteristic being equivalent to an input/output impedance among 4 lines and ground. CONSTITUTION:The switch circuits 22, 23 are coupled respectively between the midpoints 20, 21 of the 2 lines 14, 15 having the impedance equivalent to the input/output impedance among the 4 lines 12-15 and ground. Through the constitution above, when the switch circuits 22, 23 are opened, they act like a hybrid ring, the which a reception power of one side of two input terminals 16, 17 is synthesized and the power is outputted from the other terminal 19, and in grounding the switch circuits 22, 23, the transmission power of the other terminal 19 is outputted from the terminal 17 and also the circuit constitution is very simple, then the reliability is improved and small size and light weight are attained.

Device for reducing pulse noise

Abstract: PURPOSE:To simplify the circuit arrangement and provide an inexpensive device by using the device comprising a switch circuit interrupting the signal transmission while pulse noise is produced by a control signal and a series circuit consisting of the 1st capacitor, the 2nd capacitor and a resistor at the output side of the switch circuit. CONSTITUTION:A switch 20 is brought into OFF-state by a control signal Sb generated in a control signal generating circuit CSG at the period corresponding to the position where pulse noises N1, N2, N3 in an input audio signal Sa exist, and the said switch 20 is brought into ON-state during the period when no pulse noises N1, N2, N3 exist in the input audio signal Sa. Since an output impedance of an amplifier 19 is very low, a terminal voltage of a capacitor 24 at the time when the switch 20 is brought into ON-state as mentioned above is equal to a voltage of the input audio signal Sa, and this voltage is outputted to an output terminal 25 via a non-inverting amplifier 21.

Input and output circuit

Abstract: PURPOSE:To stabilize the potential of a bonding pad without flowing steadily a current by adding a CMOS-FF constitution circuit (FF) for pull-up or pull-down to the bonding pad connected to a bidirectional input/output circuit CONSTITUTION:When an output enable signal (INE)OE is in the low level and an output tristate buffer 4 has a high output impedance, an FET11 of an FF1 is turned on, and the voltage of a bonding pad 2 is pulled up to VDD If an internal signal D'0 and the (INE)OE become high-level in this state, an FET41 is turned on, and the voltage of the pad 2 becomes VSS Simultaneously, an inverter 10 of the FF1 is inverted to turn on an FET12, and this state is held, and therefore, the voltage of the pad 2 is pulled down as it is even if the (INE)OE is inverted to the low level thereafter Consequently, the pad 2 can be always set to the pulled-down or pulled-up state, and the input signal is stabilized