External RC Research Articles

Optically controlled optical gate with an optoelectronic dual diode structure – theory and experiment

A low-power, surface-normal optically controlled optical gate that incorporates two stacked AlGaAs diodes has been tested using both picosecond and femtosecond pulses. The device opens and closes within 20 ps with a 30% reflectivity change. Repeated gating with 20 ps periods has been demonstrated – a repetition period significantly faster than the external RC time constant. A theory of the dynamics of optically induced voltage across multiple-layered structures is presented and has been incorporated into simulations, matching experimental results well. This theory also provides insight into both the form and possible improvement of the device recovery using multiple layers.

Countercurrent Heat Exchangers with Both Fluids Subjected to External Heating

A mathematical model was developed to study the performance of a counterflow heat exchanger in which both fluid streams are exposed to external heating. It was found that under the external heat transfer condition, the effectiveness of the heat exchanger was drastically reduced. The hot fluid temperature effectiveness increased as the external thermal conductance ratios, Rh and Rc, decreased. For effective operation and to avoid temperature cross, there exist a maximum possible NTU for a given Rh and Rc.

Coupling of Josephson flux-flow oscillators to an external RC load

We investigate by numerical simulation the behaviour of the power dissipated in a resistive load capacitively coupled to a Josephson flux-flow oscillator and compare the results to those obtained for a d.c. coupled purely resistive load. Assuming realistic values for the parameters R and C, both in the high- and in the low- case the power is large enough to allow the operation of such a device in applications.

A serial bus transceiver for the automotive environment

A custom monolithic integrated circuit used as a direct interface between a single-wire data link and microcomputer assemblies in the harsh automotive environment is described. Unusual circuitry allows operation from a single 5-V supply with a grounded substrate despite 6-V ground differences between the nodes. The IC features a 10-mA tristate output with a voltage swing to within 1/2 V of each rail. In addition, the output maintains the high-impedance state during loss of ground and through shorts to -16 and +16 V, remains stable for unlimited capacitive loads, and provides protection from short circuits and high-voltage transients. On-chip waveshaping referenced to an external RC time constant approximates a third-order filter for precise control of rise times and radiated noise in transmitted data. The differential receiver accepts voltage levels from -6 to +12 V and filters input signals for noise immunity. Bit rates to 9600 baud are possible in the described application.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A precision monolithic time delay generator for use in automotive electronic fuel injection systems

A high-performance low-cost IC time-delay generator has been developed to be used as a building block for automotive electronic fuel injection systems. Time-delay accuracies are achieved by employing the IC to precisely control both the reset time and the initial ramp voltage of an external RC voltage sweep circuit by means of a gated voltage regulator. Reference information, derived from the rotating distributor shaft, triggers an input flip-flop that controls a reset generator to produce the required gating pulses. The resulting exponential voltage sweep is sensed at the input of three externally programmable voltage comparators that provide three separate time-delayed output signals within a /spl plusmn/1-percent accuracy from -40/spl deg/ to +125/spl deg/C. This technique is contrasted to a linear voltage sweep approach which offers less desensitivity to IC parameter variations.

Voltage Pulse Profile Characteristics with Space Charge of a Loaded Pulsed Ionization Chamber

An analytical model describing the voltage pulse profile of a pulsed ionization chamber and its relationship to the electron density in a field drift dominated plasma is formulated. The differential equation derived from the equations of motion and conservation of electron density combined with Poisson's equation for the electric space-charge field in the system is solved analytically for the cylindrical-electrode geometry with an external RC circuit. The numerical analysis for the given initial and boundary conditions yields the anode voltage-signal pulse profiles for the period of electron collection as a function of the initial electron density, the gas pressure, and ion-chamber radii and length. Thus, the theory permits the determination of the electron density from the observed voltage signal.

A New Method for the Measurement of Cathode Interface Impedance

A new simple and sensitive bridge method for the measurement of cathode interface impedance is reported in this paper. A tube with an interface impedance under test in this method forms a bridge together with a reference tube with no interface layer and with an external variable RC circuit in its cathode return. The bridge is excited by a set of three sinusoidal signals of 200 kc, 1.1 and 5 Mc. The unknown interface impedance is then measured by simultaneously balancing the bridge for these frequencies. The detector consists of amplifiers tuned to each frequency and a cathode-ray oscilloscope that displays each signal separately. A small wobbling of the transconductance in the reference tube is also provided for simplifying the measurement and overcoming drift of tube characteristics. This bridge has a sensitivity of the order of 0.002 rad as a minimum detectable phase shift, and allows a measurement of interface resistances as low as a few ohms with time constants of 0.01 μsec or more, even in ordinary tubes.