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Full hybrid-pi model. The full model introduces the virtual terminal, B′, so that the base spreading resistance, r bb, (the bulk resistance between the base contact and the active region of the base under the emitter) and r b′e (representing the base current required to make up for recombination of minority carriers in the base region) can be represented separately.
Figure 2: Adding an emitter resistor decreases gain, but increases linearity and stability. Common-emitter amplifiers give the amplifier an inverted output and can have a very high gain that may vary widely from one transistor to the next. The gain is a strong function of both temperature and bias current, and so the actual gain is somewhat ...
Figure 2: A negative-feedback amplifier. 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.
For R S values in the vicinity of r E the amplifier is transitional between voltage amplifier and current buffer. For R S ≫ r E the driver representation as a Thévenin source should be replaced by representation with a Norton source. The common base circuit stops behaving like a voltage amplifier and behaves like a current follower, as ...
A translinear circuit is a circuit that carries out its function using the translinear principle. These are current-mode circuits that can be made using transistors that obey an exponential current-voltage characteristic—this includes bipolar junction transistors (BJTs) and CMOS transistors in weak inversion.
The result is that the BJT makes a good switch that is controlled by its base input. The BJT also makes a good amplifier, since it can multiply a weak input signal to about 100 times its original strength. Networks of BJTs are used to make powerful amplifiers with many different applications. In the discussion below, focus is on the NPN BJT.
Taking a typical length as twice the minimum, L = 2 L min = 0.130 μm and a typical value of λ ≈ 1/(4 V/μm L), we find 1/λ ≈ 2 V, and g m r O ≈ 110, still a large value. [ 8 ] [ 9 ] The point is that because g m r O is large almost regardless of the technology, the tabulated gain and the output resistance for both the MOSFET and the ...
[1] [2] [3] The Widlar circuit may be used with bipolar transistors, MOS transistors, and even vacuum tubes. An example application is the 741 operational amplifier, [4] and Widlar used the circuit as a part in many designs. [5] This circuit is named after its inventor, Bob Widlar, and was patented in 1967. [6] [7]