Voltage, current, and charge control, Electrical Engineering

Voltage, current, and charge control:

The collector-emitter current can be seen as being controlled through the base-emitter current (current control), or through the base-emitter voltage (voltage control). These views are associated by the current-voltage relation of the base-emitter junction that is just the usual exponential current-voltage curve of a p-n junction (diode).

The physical description for collector current is the quantity of minority-carrier charge in the base region. Detailed models of transistor action, like the Gummel-Poon model, account for the distribution of this charge explicitly to describe transistor behavior much more exactly. The charge-control view simply handles phototransistors, in which minority carriers in the base region are made by the absorption of photons, and handles the dynamics of turn-off, or recovery time, which depends upon charge in the base region recombining. Though, because base charge is not a signal which is visible at the terminals, the current- and voltage-control views are usually employed in circuit design and analysis.

Within analog circuit design, the current-control view is sometimes employed because it is approximately linear. i.e., the collector current is almost βF times the base current. Some fundamental circuits can be considered by assuming that the emitter-base voltage is approximately constant, and that collector current is beta times the base current. Though, to accurately and reliably design production bipolar junction transistor circuits, the voltage-control (for instance, Ebers-Moll) model is needed. The voltage-control model needs an exponential function to be taken into consideration, but while it is linearized such that the transistor can be modeled like a transconductance, like in the Ebers-Moll model, design for circuits like differential amplifiers again becomes a mostly linear problem, thus the voltage-control view is frequently preferred. For translinear circuits, where the exponential I-V curve is key to the operation, the transistors are generally modeled as voltage controlled with transconductance proportional to collector current. Usually, transistor level circuit design is carried out by using SPICE or a comparable analogue circuit simulator, so model complexity is generally not of much concern to the designer.

Posted Date: 1/10/2013 6:37:10 AM | Location : United States

Related Discussions:- Voltage, current, and charge control, Assignment Help, Ask Question on Voltage, current, and charge control, Get Answer, Expert's Help, Voltage, current, and charge control Discussions

Write discussion on Voltage, current, and charge control
Your posts are moderated
Related Questions
Why rhehostat is not used in the field of dc series motor

Q. What are the benefits of ccs over in-channel signalling? The benefits of CCS over in-channel signalling are listed below: a. Information can be exchange between processor

Explain the properties of low resistivity materials. Low resistivity materials: The conducting materials containing resistivity from 10 -8 to 10 -6 ohm-m come under this cl

Define Serial In - Parallel Out Shift Registers? For this type of register data bits are entered serially in the same manner as discussed in the last section and the difference

Q. "Developing countries could delay opening the capital account until the domestic financial system is strong enough to withstand the sometimes flow of world capital and violen

what is the method to do this project and what material used for?

What is basic requirement of semiconductor laser? Draw its label diagram and explain its working with necessary theory. Write down the applications of semiconductor laser.