Emitter Configuration Research Articles

Scattering and noise parameters of four recent microwave bipolar transistors up to 12 GHz

The scattering and the four fundamental noise parameters of four recent bipolar transistors with the largest f <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</inf> values are determined and compared for the emitter configuration. Furthermore, the construction of a variable short for the suppression of image frequencies is given.

Characteristics of the composite transistors

The expressions for the current amplification, voltage amplification, input resistance and output, resistance of the composite junction transistor in terms of The resistance parameters of the individual transistor in the common base, common emitter and common collector configurations are derived. It. is found that the composite arrangement, in general, has (i) a much higher current gain and input resistance, and (ii) smaller voltage gain and output. resistance in all the three configurations. The characteristics of the composite system are greatly modified when the second junction transistor is replaced by a point contact, type. This is discussed and practical applications pointed out.

Cross-modulation figure of merit for transistor amplifier stages

This article concerns itself with comparison of transistor amplifier configurations in relation to their cross-modulation distortion characteristics. Only the base-emitter junction nonlinearity is considered, since this nonlinearity is considered to be the most significant contributor to cross-modulation distortion. For this case investigations have shown that since cross modulation occurs because of a third-order nonlinearity, the cross-modulation distortion is therefore proportional to the square of the interfering voltage which appears across the base-emitter junction. In this article the cross modulation of the transistor stage is analyzed from its equivalent circuit rather than from the theoretical device characteristics, It is assumed that the transistor stage gain and input impedance remain relatively constant with small signal voltage excursions. Using these hypotheses, a figure of merit factor is derived for comparison of transistor and transistor amplifier configurations with respect to their cross-modulation distortion characteristics. This figure of merit factor is then used to compare the relative cross-modulation susceptibility of the common collector, common emitter, and common base configurations. All three configurations are compared in the hypothetical voltage-generator and short-circuit load case. The derivation of the equations is shown in Appendix I. For this case it is shown that the three configurations have equal figures of merit. The latter two configurations are then analyzed and compared for the more practical matched input and matched output (maximum power transfer) case. Familiar formulas for transistor gain and input impedance in the low-frequency equivalent model are used for this analysis. Derivations of the equations are shown in Appendix II. The effect of feedback on the cross-modulation figure of merit is then analyzed using both degenerative and regenerative types of feedback. It is then shown that by use of the analysis of the low-frequency model, together with the analyses of the effects of feedback, a high-frequency analysis of cross-modulation figure of merit can be made. This analysis is most applicable to wide-band VHF amplifiers, such as used in Community Antenna Television trunk cascades. A convenient means for analysing cross modulation in the more complicated high-frequency circuit is thus described. Other types of stages, such as push-pull and parallel outputs, are also discussed in regards to the defined cross-modulation figure of merit. A set of conclusions concerning the defined cross-modulation figure of merit is then reached.

Resistance parameters of composite transistors†

The resistance parameters and the simplified equivalent circuit of the two stage composite transistor configuration in terms of the parameters of the individual transistor in the common emitter configuration are derived. The analysis applicable to the calculations of current gain, input and output resistances, voltage gain and power gain of the composite configuration is extended for a composite transistor circuit consisting of an arbitrary number of transistors. The results are found in agreement with those derived by others.

A Current-Mode Trigger Pulse Generator for Fast Coincidence Circuits

The design and philosophy of a new current-mode trigger pulse generator are described. The pulse generator uses two transistors in a coupled emitter configuration and only ordinary components. The output impedance at collectors is 93 ohms though this may be reduced where it is desired to match other transmission line impedances. Rise time is less than 3 nanoseconds with jitter in the 10-11 second range. Pulse output is ±2.5 volts and extremely clean and square with little undershoot or overshoot. Pulse length may be chosen, in the normal way, to be from ~10 nsec. up to microseconds. The circuit may be retriggered as soon as the output has recovered to zero. Its layout will be discussed and also its use as a replacement for limiter circuits in fast coincidence measurements.

Anomalous Photocurrent Generation in Transistor Structures

It has been previously reported that, at relatively modest dose-rates (~109 rad/sec), certain transistor types exhibit an anomalous primary photocurrent response which results in serious departures from the commonly assumed linear dose-rate dependence. This paper presents additional experimental evidence concerning the anomalous photocurrent problem and develops a model which explains the observed data in terms of carrier generation and transport processes within the device. The analysis and supporting experimental evidence shows that the observed phenomenon is the result of base-emitter junction breakdown. This breakdown is induced by transverse photocurrent flow in the active base region and causes the device to assume a common emitter configuration wherein the primary photocurrent is amplified by the device gain.

On Some Physical Parameters of Uniform Base Junction Transistors

ABSTRACTIn the following paper the authors have described a new method of estimating some important physical parameters of uniform base junction transistors, operated at low injection levels. By measuring the voltage feedback factor h12 in the common base configuration a method of evaluating the ‘emitter efficiency term’ E, and by studying the variation of short circuit current amplification factor (β) and the base emitter junction voltage Ve (d.c.), with d.c. emitter current Ie in the common emitter configuration, the recombination coefficient and the hole and electron densities in the base region have been evaluated. The method described in the following paper which is applicable to the p-n-p transistors, is also applicable to n-p-n transistors as well by appropriately changing the signs.

Determination of Some of the Physical Parameters of Alloy Junction Transistors

ABSTRACTBy measuring the low frequency current amplification factor and the hybrid parameters in the common emitter configuration a sufficiently accurate method of evaluating some physical parameters of a uniform base alloy junction transistor is described. By plotting h12e versus h22e/Ie an accurate method of evaluating the junction temperature and by measuring the applied base emitter voltage at various emitter currents, a new method of evaluating the conducting cross-section are given. The transition capacitances at both emitter and collector junctions are also calculated. The method is applicable at low injection levels only.

Switching waveform prediction of a simple transistor inverter circuit

This paper presents a brief review of charge control equations for base step current drive transistor switching in the grounded emitter configuration. On the basis of these equations, transient switching waveforms are calculated by a simple piecewise analysis procedure. A switching locus on the ω <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</inf> vs. I <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</inf> curve for the determination of the transient waveforms is introduced. A comparison of experimental and theoretical rise time waveforms demonstrates good correlation between theory and experiment.

A wide-band low noise L-band balanced transistor amplifier

The design principles, construction details, and experimental results of a balanced transistor amplifier suitable for precise wide-band applications in the low microwave frequency range are described. Each amplifier stage consists of a pair of electrically similar transistors whose input and output signals are combined by 3-dB directional couplers. This eliminates the need for tuning adjustments. For a wide frequency range, the main advantages of the balanced design over more conventional multistage amplifiers are 1) improved input and output impedance matching, gain flatness, phase linearity, gain compression, and intermodulation characteristics, 2) possible designing of the amplifier simultaneously for minimum noise figure and good input match, 3) relatively little effect on overall amplifier gain and matching by changes in the distribution of transistor impedance characteristics, provided that transistors can be selected in similar pairs. The amplifier gain is easily controlled over a wide range by the dc bias with little degradation of the gain flatness and impedance matches. To obtain these advantages, a second transistor is required for each amplifier stage. A four-stage balanced amplifier was designed and constructed in printed circuit form for L-band operation, using Western Electric GF-40037 transistors in the common emitter configuration. The transistors were paired in a test circuit so that their input or output impedances were within about ten per cent. (With the current GF-40037 distribution, this takes less than five random tries on the average.) Without any tuning adjustments, the following characteristics were obtained over a 20 per cent (and 60 per cent) frequency band in the 0.8 to 1.6-Gc/s range: Gain = 20 dB ± 0.2 dB (±0.5 dB) Reverse Loss >50 dB (>40 dB) Phase A and f B , power out at 2f A - f B and 2f B - f A ≃ -50 dBm. The 3-dB bandwidth points are at 650 Mc and 1700 Mc, and the voltage standing-wave ratios (VSWR's) over this range are under 2. The transistors are operated at I e = 2 to 4 mA and V CB = 5 to 6 volts, depending on the stage. The total dc power consumption for the four-stage amplifier is about 50 mA at 7.5 volts.

Internal thermal feedback in four–poles especially in transistors

Thermal-electric interaction or internal thermal occurs in temperature dependent devices and four-poles at low frequencies, if the thermal time constants are small. An electrical equivalent circuit which describes this thermal effect is generally derived and applied to transistors in common base and common emitter configuration. It consists of current sources and of resistance-inductance circuits which can be directly related to the thermal equivalent circuit of the device. It is shown that this thermal feedback should not be neglected in the measurement of high-frequency transistors, in the design of dc or video amplifiers and voltage or current regulators. Some measurements are reported and discussed. For instance, a strong frequency dependence of some four-pole parameters, especially of the forward trans-conductance y 21 and the short circuit output admittance y 22e of high frequency transistors was found at frequencies below 1 Mc. These effects can be explained by the new equivalent circuit. Possible application of this thermal-electric interaction may include the realization of large low Q inductances for low frequency integrated circuitry, and perhaps the investigation of pinch-in and second breakdown effects. It appears that the low frequency noise figure of transistors may also be affected by this effect.

Predicting transistor storage time for nonstep, quasi-voltage inputs

The differential equation which has been derived by earlier workers for minority carrier storage in the base of a one-dimensional transistor model has been solved for storage time assuming a general, time dependent, OFF base current. Specific base currents treated include those encountered when driving the base with a step, ramp, or exponential voltage in series with a speed-up network. The theoretical results are compared with the storage time observed for germanium mesa, MADT,d PADT, and epitaxial transistors in the common emitter configuration. Although the solution obtained assumes minority carriers are stored predominately in the base, the agreement between theory and observed results for mesa units, which have carrier storage in the collector also, is good.

Highly linear amplification with transistors

Highly linear amplification can be obtained with HF diffused-base transistors in the common base configuration. It is the purpose of this paper to 1) present experimental results to demonstrate this, 2) demonstrate the causes for this high degree of linearity and derive expressions for optimum bias voltages and currents (these results can be extended with certain restrictions to the common emitter and common collector configurations), and 3) present a general method for analytically treating nonlinearity in all transistor configurations. A push-pull amplifier using 2N509- or 2N1195-type transistors provided 13 db of gain, with signal-to-distortion ratios of 70 to 80 db for broad-band white noise signals with +3 dbm of average output power or sine wave signals with +15-dbm peak output power. The stability of this gain and linearity with temperature and interchange of transistors is high. This high degree of linearity is shown to be due to 1) cancellation of current sensitive nonlinearity in the emitter and collector resistances, 2) collector voltage bias adjusted so that the derivative of the collector conductance with respect to collector voltage is zero, and 3) the use of a high alpha cutoff frequency transistor. An expression derived for optimum bias was in good agreement with experiment. The nonlinear distortion in transistors is shown to be different from that found in most devices, in that there are frequency-sensitive and frequency-insensitive nonlinearities. A general analysis carried out including these terms was in good qualitative agreement with experiment.

Transistor behavior at high frequencies

The tee equivalent circuit for junction transistors has been modified to take account of electric field in the base region. This electric field is the result of a graded impurity density in the base region of the transistor. It is shown that a graded base improves the high-frequency performances of the common base stage; however, the improvement in common emitter performance is considerably less because of the increased excess phase which accompanies the improved high-frequency performance. The complex hybrid parameters are calculated for the common base and common emitter configurations; these calculations take into account the parasitic interterminal capacities of the transistor. The common emitter calculations are compared to measured data, and substantial agreement is obtained.

Transistorized Distributed Amplifier

Some analytical and experimental results are given for a transistorized distributed amplifier using the common emitter configuration. The characteristic impedances of the base and collector transmission lines are both 43.4Ω. A 4-section amplifier stage yields a mid-frequency gain of 5.1 db and an upper half-power frequency of 290 Mc. The low-frequency response is reasonably constant down to 10 cps.

Transistor Simulator

An apparatus allowing a straightforward determination of the π equivalent circuit of alloy junction transistors is described. The principle of measurement is based on the simulation of wave forms. The possibility of a simple determination of the equivalent circuit at any working point of the transistor enables a rapid evaluation of the current or voltage dependence of the circuit elements. The equipment, having an upper frequency limit of 10 Mc, can be used for transistors of much higher alpha cutoff frequencies, since for the measurements the common emitter configuration is chosen. Examples are given to demonstrate how some physical and dimensional values of the transistor can be calculated from the measured parameters.

NATURAL EQUIVALENT CIRCUIT AND HYBRID PARAMETERS OF JUNCTION TRANSISTOR

In this paper the relationships between small-signal h-parameters and elements of the natural equivalent circuit of the common emitter configuration of junction transistors are studied. From experimental results of h-parameters of two typieal alloyed PNP transistors (one 2N104 and one п-6 transistor) the relationship of h-parameters and elements of natural equivalent circuit vs operating frequency and d. c. operating condition (d.c. emitter current and d.e. collector voltage) are evaluated. Results thus obtained ace then compared with results obtained from analysis based on calculations using physical constants of the transistor. The explanation of the behavior of the reverse open-circuit voltage amplification factor, μbc, of the common emitter circuit is given in detail. Characteristics of μbc and properties of h22 (the output admittance with input open) are correlated. This paper gives complete information about h-parameters and natural equivalent circuit of two transistors, serving as an important reference for both device men and research workers on transistor circuits.

The effect of collector capacity on the transient response of junction transistors

The effect of collector depletion layer capacity on the transient response of junction transistors to a current input is calculated for the case of a resistive load. Expressions are given for the small-signal rise-time of the common-base, emitter, and collector configurations and for the large-signal turn-on and decay times of the common-emitter and collector configurations. The analysis shows that the transient durations under most conditions of operation are approximately ( 1 + \omega_{\alpha}R_{L}C_{c} ) times those which would be predicted for the short-circuit output approximation reported by Moll [1]. Experimental results are reported which exhibit an excellent agreement with the analysis over a wide range of \omega_{\alpha}R_{L}C_{c} . An empirical examination has been made of the dependence of large-signal switching time on the range of operating point excursion. A satisfactory approximate representation of this dependence is provided by a first-order correction factor, which takes into account the functional dependence of ω α and C c on collector voltage.

Behavior of Noise Figure in Junction Transistors

It is well-known that generator resistance and dcemitter current are two major factors in determining the noise figure of junction transistors. Other important factors are base resistance, low-frequency alpha, and alpha cutoff frequency. A method of calculating the noise figure in terms of these parameters, the frequency variation of the noise figure, and the conditions for minimizing the noise figure are presented. The results provide means for specifying transistor and circuit parameters to meet noise requirements. In the absence of "excess" or 1/f noise, the noise figure as a function of frequency for the common base, common collector, and common emitter configurations is constant up to √1-a0 fa. Here a0 is the low-frequency alpha and fa the alpha cutoff frequency. Above this frequency the noise figure increases toward an asymptote of 6 decibels per octave. Calculations show that for minimum noise figure the base resistance and emitter current should be small, a0 should be close to one, fa should be large, and the driving source resistance has an optimum value. This work is based on a simplified version of a transistor noise equivalent circuit developed by van der Ziel.

Design principles for junction transistor audio power amplifiers

Junction transistors may be employed as audio frequency power amplifiers which will supply up to several watts of output power. The fact that there are two basic types of transistor (n-p-n and p-n-p) allows a freedom of circuit design which is impossible with electron tubes. In power amplifier design the usual small signal assumptions cannot always be considered valid. Hence, large signal techniques must be applied in order to describe the behavior of the device. The non-linear distortion associated with large signal operation is discussed in terms of the transistor characteristics and methods of reducing this distortion are outlined. Operation in several circuit connections is considered with particular emphasis on the common emitter configuration.