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The common-emitter circuit is the most widely used of junction transistor amplifiers. As compared with the common-base connection, it has higher input impedance and lower output impedance. A single power supply is easily used for biasing. In addition, higher voltage and power gains are usually obtained for common-emitter (CE) operation.
In electronics, a common collector amplifier (also known as an emitter follower) is one of three basic single-stage bipolar junction transistor (BJT) amplifier topologies, typically used as a voltage buffer. In this circuit the base terminal of the transistor serves as the input, the emitter is the output, and the collector is common to both ...
Terminal 3 (common), emitter; giving x to be e; i i, base current (i b) i o, collector current (i c) V in, base-to-emitter voltage (V BE) V o, collector-to-emitter voltage (V CE) and the h-parameters are given by: h ix = h ie for the common-emitter configuration, the input impedance of the transistor (corresponding to the base resistance r pi).
The narrowing of the collector does not have a significant effect as the collector is much longer than the base. The emitter–base junction is unchanged because the emitter–base voltage is the same. Base-narrowing has two consequences that affect the current: There is a lesser chance for recombination within the "smaller" base region.
In graphical analysis of nonlinear electronic circuits, a load line is a line drawn on the current–voltage characteristic graph for a nonlinear device like a diode or transistor. It represents the constraint put on the voltage and current in the nonlinear device by the external circuit. The load line, usually a straight line, represents the ...
Low-voltage positive emitter-coupled logic (LVPECL) is a power-optimized version of PECL, using a positive 3.3 V instead of 5 V supply. PECL and LVPECL are differential-signaling systems and are mainly used in high-speed and clock-distribution circuits. A common misconception is that PECL devices are slightly different from ECL devices.
For example, a common base may be used as a current buffer at the output of a common emitter stage, forming a cascode. This will typically reduce the Miller effect and increase the bandwidth of the amplifier. Alternatively, a voltage buffer may be used before the amplifier input, reducing the effective source impedance seen by the input terminals.
Fig. 1 shows the common-base Colpitts circuit. The inductor L and the series combination of C 1 and C 2 form the resonant tank circuit, which determines the frequency of the oscillator. The voltage across C 2 is applied to the base-emitter junction of the transistor, as feedback to create oscillations. Fig. 2 shows the common-collector version.