Transistor duty cycle

A limited amount of trapping (either intrinsically or extrinsically) is helpful in that it ensures a deep OFF state of the device during the time at which other lines are addressed that is a (properly adjusted) hysteresis can serve as a memory element over the frame time (Ast, 1982a,b, 1983). This argument is not readily accepted by those who believe that a device must be inherently stable to function in a reliable manner. However, Luo et al. (1983) arrived at an identical conclusion in their analysis of the switching performance of CdSe transistors in matrix-addressed LC displays. It is very important that the trapping be noncumulative. Since the duty cycle of a... 

We will see later that the characteristics of vacuum triodes are replicated in npn junction transistors, albeit by a very different mechanism. One can operate very well with vacuum tubes, but they are more costly and difficult to manufacture and are prone to relatively early failure, mainly due to the tube becoming "gassy" with the evaporation of W from the filament or from vacuum breakdown, due to the prolonged heating of the vacuum tube. The typical vacuum tube duty cycles (a few thousand hours) are much inferior to the duty cycles of transistors. 

The component in the amplifier that must be analyzed is the transistor. As defined the MIL-HDBK-217, its failure rate depends strongly on the temperature, the duty cycle and the junction temperature. All these parameters must be taken into account on the amplifier design. 

Assume that a 25% duty cycle represents the halfway point between off and fidl on (50%) for each transistor set. Modulating up or down from 25% drives the amplifier to zero and 50% duty cycle for each set (100% total). The average of the output voltage across R will follow the pulse width represented drive signal. The output must be low-pass filtered to obtain the average, which is a reproduction of the signal to be amplified. (Use of the Class D amplifier in this way is sometimes referred to as Class S.)... 

This low-cost type of transistor tester uses digital high current, low duty cycle pulse-testing technique to test semiconductors even with resistive and capacitive shunt Impedances. 

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