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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 ...
Examples are imperfect voltage followers (emitter, source, cathode follower, etc.) and amplifiers with series negative feedback (emitter degeneration), whose input impedance is moderately increased. The op-amp non-inverting amplifier is a typical circuit with series negative feedback based on the Miller theorem, where the op-amp differential ...
Diagram from Widlar's original patent. A Widlar current source is a modification of the basic two-transistor current mirror that incorporates an emitter degeneration resistor for only the output transistor, enabling the current source to generate low currents using only moderate resistor values.
A typical example are Howland current source [2] and its derivative Deboo integrator. [3] In the last example (Fig. 1), the Howland current source consists of an input voltage source, V IN, a positive resistor, R, a load (the capacitor, C, acting as impedance Z) and a negative impedance converter INIC (R 1 = R 2 = R 3 = R and the op-amp).
See also an example of a mirror with emitter degeneration to increase mirror resistance. For the simple mirror shown in the diagram, typical values of will yield a current match of 1% or better. Figure 2: An n-channel MOSFET current mirror with a resistor to set the reference current I REF; V DD is positive voltage.
In electronics, emitter-coupled logic (ECL) is a high-speed integrated circuit bipolar transistor logic family. ECL uses an overdriven bipolar junction transistor (BJT) differential amplifier with single-ended input and limited emitter current to avoid the saturated (fully on) region of operation and the resulting slow turn-off behavior. [2]
The transistor continuously monitors V diff and adjusts its emitter voltage to equal V in minus the mostly constant V BE (approximately one diode forward voltage drop) by passing the collector current through the emitter resistor R E. As a result, the output voltage follows the input voltage variations from V BE up to V +; hence the name ...
Another common example of the use of decoupling capacitors is across the emitter bias resistor of transistor common emitter amplifiers to prevent the resistor absorbing a portion of the AC output power of the amplifier. Lossy ferrite beads may also be used to isolate or 'island' sections of circuitry. These add a high series impedance (in ...