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The use of a cascode (sometimes verbified to cascoding) is a common technique for improving analog circuit performance, applicable to both vacuum tubes and transistors.The name "cascode" was coined in an article written by Frederick Vinton Hunt and Roger Wayne Hickman in 1939, in a discussion on the application of voltage stabilizers. [3]
Common collector stages have no voltage gain but high current gain and low output resistance. The load can thus draw high current without affecting the amplifier performance. A cascode connection (common emitter stage followed by common base stage) is sometimes found. Audio power amplifiers will typically have a push-pull output as the final stage.
This configuration is used less often than the common source or source follower.However, it can be combined with common source amplifiers to create cascode configurations. . It is useful in, for example, CMOS RF receivers, especially when operating near the frequency limitations of the FETs; it is desirable because of the ease of impedance matching and potentially has lower noi
The cascode (a contraction of the phrase cascade to cathode) is a two-stage amplifier composed of a transconductance amplifier followed by a current buffer. In valve circuits, the cascode is often constructed from two triodes connected in series, with one operating as a common grid and thus acting as a voltage regulator , providing a nearly ...
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.
A telescopic amplifier provides higher gain (due to higher output resistance) and higher bandwidth (due to smaller non-dominant pole at the cascode node). In contrast, it has limited output swing and difficulty in implementation of unity-gain buffer.
A transconductance amplifier (g m amplifier) puts out a current proportional to its input voltage. In network analysis, the transconductance amplifier is defined as a voltage controlled current source (VCCS). These amplifiers are commonly seen installed in a cascode configuration, which improves the frequency response.
The result is that new designs tend to use some variant of a wide swing cascode current mirror configuration. [10] [14] [15] In the case of extremely low power supply voltages of one volt or less, the use of current mirrors may be abandoned entirely. [16]