Abstract: Shield of telecommunications cable is grounded through negative impedance converter to reduce induced voltage in conductors in the cable caused by electromagnetic field of nearby powerline.

Abstract: A high-frequency negative resistance circuit for use in a voltage controlled crystal oscillator has a pair of input terminals thereby defining an input current and input voltage. The high-frequency negative resistance circuit includes a sensing circuit for sensing the input current, a biasing voltage source and a load impedance connected to the voltage source. The high-frequency negative resistance circuit further comprises a current mirror circuit connected to the sensing circuit and to the load impedance for producing a current in the load impedance. The current in the load impedance is approximately equal to the input current. The current mirror circuit also controls the sensing circuit to cause the input voltage to decrease as the input current increases. Decreasing input voltage with increasing input current defines the negative resistance. When this negative resistance circuit is configured with a crystal and a voltage controlled capacitance, an oscillator capable of high-frequency operation results.

Abstract: FET circuitry is described which may be substituted for a programmable unijunction transistor particularly on CMOS-FET integrated circuits. The FET circuitry is arranged between first and second terminals defining a conduction path exhibiting a negative resistance characteristic and a control terminal for establishing the peak voltage of such characteristic. A P-type MOS transistor has its source and gate electrodes respectively connected to the first and control terminals. A current mirror amplifier comprising N-type MOS transistors has its input terminal connected to the drain electrode of the P-type transistor, its output terminal connected to the control terminal and its common terminal connected to the second terminal of the circuitry.

Abstract: An operational amplifier having an extremely high gain-bandwidth product. The amplifier includes a gain cell with an active negative resistance circuit made up of two matched NPN transistors (18 and 20) with their bases cross-connected to their collectors, and with a differential pair of NPN transistors (14 and 16) having their emitters degenerated through the active negative resistance circuit. The value of the negative resistance is chosen to negate other resistance values in the denominator of a fraction expressing overall amplifier gain, which is therefore maximized. Since no PNP transistors are needed to maximize gain in the amplifier, NPN transistors can be used exclusively, and the amplifier can be more conveniently fabricated in integrated-circuit form, with a desirably wide bandwidth.

Abstract: A negative resistance element having two terminals (11, 12;) a resistor (R1-4) connected in a path between the terminals, and a current mirror arrangement (T1, T2; T3, T4;) responsive to a current flowing into the first terminal (11) to produce a current through the resistor R1-4 in such a direction as to increase the voltage of the second terminal 12 relative to the first terminal 11.

Abstract: An integratable circuit that simulates a source resistor comprises first and second nodes for connection to a voltage source and a virtual ground, respectively; a first integrated capacitor C1; and switch means operative for alternately electrically connecting C1's top and bottom plates to the first node and ground, respectively, and to ground and the second node, respectively, during first and second non-overlapping time periods in each time interval T for charging C1 to the source voltage and discharging C1 into the second node, respectively, where T is the time interval between adjacent second time periods and f=1/T is the switching frequency for C1.

Abstract: An electronically adjustable capacitor (varactor), an active element such as a Field Effect Transistor arranged to exhibit negative resistance, and an inductor are arranged as a frequency tunable resonator suitable for use at microwave frequencies. The negative resistance of the active element may be adjusted to compensate for the resistance of the other resonator components such that the resonator exhibits very high Q and therefore high selectivity and low loss. The resonator may be used as a filter element in a tunable filter. Alternatively the negative resistance of the active element may be adjusted such that the resonator exhibits net negative resistance and may be incorporated in a tunable reflection type amplifier.

Abstract: A filter network that exhibits a bandstop response comprises a network of basically low pass or high pass structure. The network is developed by choosing a bandstop transfer function, a fourth-orderelliptic is disclosed, which is converted to a low pass function. This function describes a passive low pass LC ladder network including a negative impedance element. A Bruton transformation is applied to the passive LC network to give an active version including an ungrounded negative resistance network in a series arm and frequency-dependent negative resistances in shunt arms without requiring inductance coils for its implementation.

Abstract: An instantaneous compressor and an instantaneous expandor both of which use the logarithmic characteristics of diodes to provide compression and expansion, respectively, of uncompressed analog PAM signals and compressed analog PAM signals. Both the compressor and expandor also include circuitry having a temperature dependent gain characteristic. The signal at the compressor output is a temperature independent compressed analog signal which follows the compressor's logarithmic encoding characteristic. The signal at the output of the expandor is a temperature independent uncompressed analog signal which is substantially identical to the analog signal at the compressor input.

Abstract: A class of two-terminal active networks which simulate low-noise temperature resistors is disclosed. A single field effect transistor or other suitable amplifier comprises the active element of the network. A dual transformer feedback arrangement or a single transformer feedback arrangement comprises the remainder of the circuit. Either positive or negative simulated resistors can be obtained with a wide range of equivalent resistance values and effective noise temperatures.

Abstract: This disclosure relates to an electronic circuit which has a controllable impedance. This type of circuit is well suited for application in noise suppression circuits or in signal compression/expansion circuits. The circuit has two stages. The first stage is a voltage to current converter. The second stage is a variable gain current amplifier. The output of the second stage is connected by a feedback loop to an input of the first stage. The circuit has a variable impedance which can be controlled by an external signal. The imput impedance of the circuit is linearly related to the applied control signal.

Abstract: A hybrid integrated impedance converter circuit comprising a frequency dependent negative resistance circuit, in which two operational amplifiers are included. Each of the two operational amplifiers has an output terminal and an inverting input terminal, with a negative feedback capacitor being connected between these terminals. The negative feedback capacitor is formed by a stray capacitance which arises between conductors connected to the output and inverting input terminals, which conductors are placed in close proximity to each other.

Abstract: An apparatus for providing simultaneously a multiplicity of independent non-interactive effects on the transmission characteristics of a voice-frequency telephone transmission line. Output voltage and current signal processing circuitry is provided which generates voltages for insertion in series with the line and currents for insertion in shunt with the line. Input voltage and current signal processing circuitry is also provided to sense the signal voltage across and the signal current through the transmission line and to generate a multiplicity of voltages and currents which are functions of the signal voltage and the signal current as well as of the voltages and currents fed back from the output signal processing circuitry to the input signal processing circuitry. A multiplicity of line conditioning control units couple the input signal processing circuitry to the output signal processing circuitry.

Abstract: A voice-frequency RC-active filter comprising a plurality of resistors and generalized impedance converter networks for synthesizing the frequency response of a preselected LC filter. Each generalized impedance converter network includes a pair of operational amplifiers and a plurality of impedances Z1, Z2, Z3, Z4 and Z5 interconnected with the amplifiers to provide the network with a driving point impedance ##EQU1## in which at least one of the impedances in both the numerator and the denominator of Zi includes a film-type resistor. At least one of the film-type resistors included in the impedances Z1, Z2, Z3, Z4 and Z5 is functionally trimmed to tune the filter. The capacitors in the filter are preferably discrete polycarbonate capacitors with a capacitance tolerance of .+-.5%, and all having the same value.

Abstract: A circuit is disclosed for impedance matching an electrical signal-generating transducer to an electrical signal-processing amplifier while substantially retaining both the original signal-to-noise power ratio and the original signal amplitude at the input to the amplifier. A load resistance of a value substantially equal to twice the characteristic resistance of the transducer is coupled across the amplifier input, while a negative low-noise resistance approximately equal in magnitude to the source resistance is coupled in series with the load resistance. A transmission line having a characteristic impedance approximately equal to the transducer resistance is coupled between the transducer output and the series-coupled load resistance and negative resistance.

Abstract: A class of two-terminal active networks which simulate low-noise-temperature resistors is disclosed. A single differential-input operational amplifier connected with a feedback resistor in an inverting amplifier configuration comprises the active element of the network. A resistive voltage divider feedback arrangement comprises the remainder of the circuit. Either positive or negative simulated resistors can be obtained with a wide range of equivalent resistance values and effective noise temperatures.

Abstract: An improved negative impedance converter is provided comprising an additional differential operational amplifier to improve signal handling capability.