Emitter Follower Research Articles

Antennas for Nonsinusoidal Waves: II-Sensors

The use of the basic large-current radiator?discussed in a previous paper?and the Hertzian electric dipole as sensor is investigated. If the sensor works into a large resistive load, typically implemented by an emitter follower, its output voltage varies like the electric field strength, while a capacitive load produces an output voltage proportionate to the integral of the field strength. The maximum energy is transferred to a load impedance that is equal to the radiation resistance of the antenna. This is the same result as in the case of sinusoidal waves, but the radiation resistance for nonsinusoidal waves differs from that for sinusoidal waves. An effective aperture can be defined, which is again analogous, but not equal, to the same concept used for sinusoidal waves.

Emitter followers and source followers as low noise pre-amplifiers for gas proportional detectors

This paper presents detailed results from noise measurements on fast pre-amplifiers for wire chamber applications. Emitter followers and source followers are compared with the well-known and widely-used common base amplifiers. The measurements show that for detectors with small stray capacitance (≤ 20pF) emitter followers and source followers give better results than common base amplifiers. Equivalent input noise charges as low as 260 electrons rms have been achieved with a gallium arsenide transistor used as a source follower (shaping time 18 ns). This value is lower by about a factor of 5 than that for a common base amplifier. Also bipolar transistors as emitter followers give good results (600 to 800 electrons rms).

Yield optimization for arbitrary statistical distributions: Part II-Implementation

A suggested test problem for proposed algorithms in yield optimization is described in detail. The problem is a current switch emitter follower (CSEF) circuit originally described by Ho, which includes a transmission line. The ideas presented in Part I of this paper [1] are applied to this circuit in order to obtain an optimal statistical design. Production yield is maximized taking into consideration statistical distributions of circuit parameters and realistic correlations between transistor model parameters. Nonlinear programming employing the analytical formuias for yield and its sensitivities is used to provide optimal nominal values for the circuit parameters. Different design specifications are assumed and corresponding optimal designs are obtained.

A 300 V//spl mu/s monolithic voltage follower

An open-loop, JFET input, high-speed buffer, designed without feedback, is described. Careful biasing of source and emitter followers ensures accurate unity gain and gain linearity with 10 mA of load current. A unique quasi-quad input FET layout provides excellent matching and thermal gradient cancellation and simultaneously optimizes speed performance. Offset voltage is permanently adjusted at wafer test by Zener-zap trimming. The output is capable of driving large capacitive loads with 70 mA of peak current.

Output inductance of an emitter follower

A small-signal analysis of a simple emitter follower is performed to ascertain its effective output inductance as a function of circuit element values, transistor parameters and signal frequencies. It is shown that the low-frequency value of output inductance is directly proportional to the common emitter shortcircuit gain-bandwidth product. Moreover, the product of this inductance and the bandwidth over which the input port of an emitter follower behaves as a low Q reactive impedance is limited solely by transistor gainbandwidth product and collector junction capacitance

A Subnanosecond Masterslice LSI Using Dielectric Isolation and Three Layer Metallization Technologies

A high speed bipolar masterslice LSI has been realized which contains 400 internal gate cells and 60 output gate cells on a 5.7 mm × 5.7 mm chip. Oxide isolation with n-type epiataxial layer and three layer metallization by PMP structure are used for fabrication process. These new technologies afford a large reduction in device size, parasitic capacitance and wiring area, which improve LSI performance. An internal gate is realized by the CML circuit with a 400 mV logic swing and with emitter followers, together with extensive use of emitter-dotting and collector-dotting. Power supply voltage is -3.2 V and output level is compatible with standard ECL. The ALU chip has been fabricated for an application of this masterslice LSI and a 1.48 ns average propagation delay per circuit has been achieved.

Differential pulse regenerator driven by 1 Gbit/s p.c.m.-type signals from an avalanche photodiode

A hybrid-integrated pulse regenerator circuit, essentially employing an ultrabroadband 180° hybrid, step-recovery diodes and bipolar-transistor emitter followers, was operated by 1 Gibt/s signals delivered from an avalanche photodiode. A voltage gain of 20 dB could be measured on a single regenerator stage. RZ output pulses of halfwidths down to 100 ps were obtained, with the pulse shape being independent of the shape of the input pulses.

Modular single-stage universal logic gate

First and second generation universal logic gate (ULG):IC's are described. The ULG comprises one-stage arrays of two identical cascade circuits. These ULG's are shown to realize all logic functions of four (and fewer) input variables in approximately the same propagation delay as a single ECL current switch emitter follower (CSEF) gate fabricated with the same processing technology. Substantial power and power-delay product advantages relative to CSEF arrays are demonstrated at comparable silicon area for realization of all four-input functions. The ULG was developed for implementing logic arrays with a minimum number of gating stages.

Thevenin’s theorem in linear circuits with controlled sources

In the analysis of electronic circuits, it is often useful to replace a network by its Thevenin equivalent circuit. To do this one needs to calculate the values of the equivalent voltage and series resistance. It is shown that the prescription for finding the equivalent resistance given by most electronic texts is not generally valid when the network contains sources whose strength is controlled by currents within the network. In fact, the source strength coefficients appear in the expression for the equivalent resistance, yet would be eliminated by the usual method of short-circuiting the sources. A correct method of derivation is given and the emitter–follower circuit is shown as an example.

Free Running Bootstrap Sawtooth Generators

This paper describes the design of free running Bootstrap Sawtooth Generators. Three sawtooth generators are described. Two of the circuits are meant for low voltage operation, one using Darlington pair and the other using constant current emitter follower in the output. The third circuit is useful for high voltage operation.

A High-Rate Phototube Base

A photomultiplier tube base designed to minimize voltage changes at the phototube's dynodes under high-rate conditions is described. Over 200 of these phototube bases are presently used on lead glass and other calorimeter phototubes in high energy physics experiments. Stiff voltage sources for dynodes are provided by making use of emitter follower characteristics of high beta, high voltage, video transistors.

Graphical Methods for the Analysis of Linear and Nonlinear Circuits

Graphical methods are developed for the analysis and design of electronic circuits, with inherent accuracies superior to those obtainable from small-signal equivalent circuits. Among the typical examples outlined are the emitter follower, the common-emitter with external emitter resistance, the Darlington Pair, the cascode amplifier, and various diode and transistor clipping circuits. Once mastered, the methods can be extended to other and more complex circuits, and to transient analysis.

A simple high performance buffer amplifier for capacitive loads

A requirement exists for a simple high performance buffer amplifier for use with capacitive loads. A suitable circuit uses a bootstrapped emitter follower in conjunction with a near unity gain feedback amplifier. Tha a.c. input impedance of the emitter follower is determined by the isolation resistance of the input terminal, the base recombination currents, and the incremental changes in base charge. Operation at low current levels permits operation at near unity gain (∼0.999) while with capacitive feedback the input impedance is equivalent to a capacitance in the ±0.1 pF range at frequencies above 1 kHz. The amplifier's voltage gain is 0.9980 ± 0.0005 (adjustable to 1.0000 ± 0.0005) and its output impedance is less than 0.1 Ω between 700 Hz and 70 kHz, for capacitive loads up to 0.01 µF. Minor alterations permit increased capacitive loading and operation at lower frequencies.

Miller long-duration sweep generator

A Miller-integrator circuit using a simple amplifier with positive feedback has been analysed. The circuit has the high input impedance inherent with insulated-gate field-effect transistors and the low output impedance characteristic of emitter followers. Owing to these properties and the high voltage gain, it is possible to obtain long-duration sweeps of good linearity. A sweep of about 2 h duration and of a linearity error of 0.05% has been obtained. The ratio of the dynamic range of the output voltage to the supply voltage is greater than 60%, and the output impedance is less than 10?.

Superintegrated voltage clamp

A monolithic implementation of a voltage clamp circuit is described that saves area and reduces capacitance, as the transistor and the voltage divider resistor required are merged into a single device. Following this principle in current switch logic circuits, even the emitter follower can be superintegrated into the collector loads. Moreover, base-bleeding resistors can be incorporated in transistors of silicon-controlled rectifiers.

On the transient response of emitter followers

Transient response of emitter followers is analyzed incorporating the effects of collector-base and load capacitances, gain-bandwidth product, excess delay, and base, collector, and load resistances. Basic considerations pertaining to transient response and instabilities are discussed, and numerical results are given for a wide range of circuit parameters.

A high input impedance buffer amplifier using bipolar transistors

Abstract The input impedance of conventional emitter follower circuits is limited due to the finite value of the passive emitter resistance, shunting effect of biasing resistors and that of intrinsic collector to base feedback admittance and also to the fall in current amplification factor at low operating currents. Further, the input admittance is frequency dependent because the device parameters involved therein are themselves frequency dependent. However, the shunt positive feedback incorporated in such circuits minimizes the shunting effect of the biasing network and also that of the intrinsic feedback admittance. The simulation of negative capacitance across the input terminals nullifies the effect of the presence of the otherwise positive capacity. This technique extends the bandwidth over which the input impedance remains constant. A typical buffer amplifier circuit employing five conventional epitaxial planar bipolar silicon transistors has been described in the present communication. The input im...

A device for generation and presentation of modulated light stimuli

A device is described which enables generation and presentation of light stimuli modulated by various wave forms and frequencies. The system consists of a solid state amplifier with emitter follower circuit which amplifies the output of a wave form generator to drive light sources mounted in goggles worn by the subject. Where color and low light intensity are acceptable, light-emitting diodes should be used as light sources because of their accurate reproduction of input wave forms. If high intensity is necessary, small incandescent bulbs can be used with certain limitations in frequency, wave form response and color due to filament warm-up and cool-down time. Mounting the light sources in goggles with individual eye cups maintains constant light source-to-eye geometry, permitting stimulation during drowsiness or sleep and eliminates extraneous visual stimuli.

Variable Frequency Three-Phase Square Wave Generator with Fixed Phase Sequence

The design of a three-phase square wave generator with continuously variable output frequency in the 40-400 Hz range is described. The basic generator circuit consists of an astable multivibrator, and a divide-by-three logic network followed by a divide-by-two logic network with a synchronizing gate. Frequency control is arranged in the multivibrator. The synchronizing gate assures fixed output signal phase sequence. Noninverted and inverted output is available. In order to provide adequate output power, push-pull load driving stages preceded by emitter followers are incorporated. Transformer coupled output is used in the prototype to drive SCRs in a high-power three-phase static frequency changer. Custom wound toroidal core transformers have been used. The rise time of the square wave at the generator output is below 3μs.

Emitter follower operating as a voltage stabilizer

Emitter follower operating as a voltage stabilizer