Transistor Converter Research Articles

The noise figure of transistor converters

The noise figure of a transistor converter may be expressed in terms of the usual transistor and circuit parameters (source resistance, base resistance, emitter-base diode impedance, current gain, cutoff frequency, and conversion conductance). Theoretical values are in good agreement with measured values.

Control of frequency and phase displacement in transistor converter circuits by means of R-C networks

A new type of adjustable-frequency transistor converter circuit, described in Part I of this paper, differs from conventional transistor converters and from transistor converter circuits incorporating frequency adjustment discussed in previous papers. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> ‾ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> In the new type, the operating frequency is independent of the applied direct voltage - not proportional to it. The switching rate is determined by the time constant of an R-C (resistance-capacitance) network so that no saturating element is required. By making either the resistor or capacitor variable, the frequency is easily controlled over wide limits, and once a setting is made, no appreciable change in frequency occurs despite large variations in the input voltage.

ANALYSIS OF JUNCTION TRANSISTOR CONVERTERS

This paper describes a detailed analysis of conversion properties of junction transistors. A new parameter "the effective conversion transconductance" is introduced for characterizing transistor converters. The effective conversion transcon-ductance of transistor converters using a PNP transistor operated at different oscillatory conditions and at various signal frequencies are studied. Main differences between transistor converters and vacuum tube converters are compared.

Phase locking of switching-transistor converters for polyphase power supplies

SWITCHING transistors may be used in conjunction with saturable-core output transformers to convert direct-voltage inputs into alternating voltages of nearly rectangular wave form.1 The output impedance is low, the over-all conversion efficiency is high, and (even in the present state of power-transistor development) output powers of tens of watts are available. Such transistor converters are therefore being considered as supply sources for magnetic amplifiers, a-c servomotors and other components used in low power servocontrol systems. For example, in air-borne military applications, transistor power supplies may replace small rotating machine inverters, which at present produce 400-cycle-persecond supplies from the aircraft battery system, with advantages in reliability and weight.

Automatic Gain Control of Transistor Amplifiers

Since transistor small signal parameters are functions of the dc emitter current (Ie) and of the dc collector voltage (Vc), gain control can be achieved by varying either Ie or Vc. The gain decreases with decreasing 1e or Vc. Using the series-parallel representation, the parameter most sensitive to Ie-variations is h11, whereas Vc-variations affect h12 and h22 considerably. In common emitter configuration changes of h21 are also important. A study of the dependance of the hii on the dc operating point explains the nature of gain variations with Ie and Vc. Satisfactory AGC circuits have been built using either Ie- or Vc-control. The control power required is very small if Ie or Vc are controlled indirectly by varying the base current. Since Ie or Vc are decreased considerably in the presence of strong input signals, the problem of distortion must be given serious consideration. Due to the variation of transistor driving point impedances, AGC may result in changes of the bandpass characteristic of tuned amplifiers. The gain of transistor converters and oscillator-converters can be controlled by conventional or special techniques.