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For an NPN open emitter output, the collector is connected to the positive voltage rail, so the emitter outputs a high voltage when the transistor is on and is hi-Z when off. For a PNP open emitter output, the collector is connected to the low voltage supply, so the emitter outputs a low voltage when the transistor is on and is hi-Z when off.
The circuit can be explained by viewing the transistor as being under the control of negative feedback. From this viewpoint, a common-collector stage (Fig. 1) is an amplifier with full series negative feedback. In this configuration (Fig. 2 with β = 1), the entire output voltage V out is placed contrary and in series with the input voltage V in.
Transistors are used for current sources on integrated circuits because they are much smaller than resistors. Because the inverter is open collector, a wired AND operation may be performed by connecting an output from each of two or more gates together. Thus the fan-out of an output used in such a way is one. However, additional outputs may be ...
A common variation omits the collector resistor of the output transistor, making an open-collector output. This allows the designer to fabricate wired logic by connecting the open-collector outputs of several logic gates together and providing a single external pull-up resistor. If any of the logic gates becomes logic low (transistor conducting ...
The picture represents a typical ECL circuit diagram based on Motorola's MECL. In this schematic, transistor T5′ represents the output transistor of a previous ECL gate that provides a logic signal to input transistor T1 of an OR/NOR gate whose other input is at T2 and has outputs Y and Y.
The fast operation of CML circuits is mainly due to their lower output voltage swing compared to the static CMOS circuits, as well as the very fast current switching taking place at the input differential pair transistors. One of the primary requirements of a current-mode logic circuit is that the current bias transistor must remain in the ...
The output open collector transistor, T11, can sink currents up to 100 mA, and is protected from polarity reversal with a reverse diode. [ 4 ] [ 5 ] The circuit does not provide protection against excessive current or overheating.
The intersections of the load line with the transistor characteristic curves represent the circuit-constrained values of I C and V CE at different base currents. [2] If the transistor could pass all the current available, with no voltage dropped across it, the collector current would be the supply voltage V CC over R L. This is the point where ...