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If the voltage is transferred unchanged (the voltage gain A v is 1), the amplifier is a unity gain buffer; also known as a voltage follower because the output voltage follows or tracks the input voltage. Although the voltage gain of a voltage buffer amplifier may be (approximately) unity, it usually provides considerable current gain and thus ...
Description: A circuit diagram of a buffer amplifier made using an operational amplifier. = = (realistically, the differential input impedance of the op-amp itself, 1 MΩ to 1 TΩ) Date: 26 January 2009: Source: Own work
Date/Time Thumbnail Dimensions User Comment; current: 16:08, 31 August 2012: 720 × 720 (7 KB): Michael9422 {{subst:Upload marker added by en.wp UW}} {{Information |Description = {{en|A simple NPN transistor amplifier circuit diagram with transistor labels.}} |Source = I created a postscript file, and converted it too SVG using the pstoedit program. |Date = ...
In this circuit, the source terminal of the transistor serves as the input, the drain is the output, and the gate is connected to some DC biasing voltage (i.e. an AC ground), or "common," hence its name. The analogous bipolar junction transistor circuit is the common-base amplifier.
Thus this circuit finds applications as a voltage buffer. In other words, the circuit has current gain (which depends largely on the h FE of the transistor) instead of voltage gain. A small change to the input current results in much larger change in the output current supplied to the output load.
In this circuit (NMOS) the gate terminal of the transistor serves as the signal input, the source is the output, and the drain is common to both (input and output), hence its name. Because of its low dependence on the load resistor on the voltage gain, it can be used to drive low resistance loads, such as a speaker.
The transition frequency of a bipolar transistor, , is the frequency at which the short-circuit common-emitter current gain falls to unity. [7] It is effectively the highest frequency for which a transistor may supply useful gain in an amplifier.
The maximum collector-to-emitter voltage for the 2N3055, like other transistors, depends on the resistance path the external circuit provides between the base and emitter of the transistor; with 100 ohms a 70 volt breakdown rating, V CER, and the Collector-Emitter Sustaining voltage, V CEO(sus), is given by ON Semiconductor. [6]