|
The cascode is a two-stage amplifier composed of a transconductance amplifier followed by a current buffer. Compared to a single amplifier stage, this combination may have one or more of the following characteristics: higher input-output isolation, higher input impedance, high output impedance, higher gain or higher bandwidth. In modern circuits, the cascode is often constructed from two transistors (BJTs or FETs), with one operating as a common emitter or common source and the other as a common base or common gate. The cascode improves input-output isolation (or reverse transmission) as there is no direct coupling from the output to input. This eliminates the Miller effect and thus contributes to a much higher bandwidth. ==History== 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 bestowed in a paper by F.V. Hunt and R.W. Hickman in 1939, in a discussion on the application of voltage stabilizers.〔Hickman, R. W. and Hunt, F. V., "On Electronic Voltage Stabilizers", ''Review of Scientific Instruments'', vol. 10, p. 6-21 (January 1939).〕 They proposed a cascode of two triodes (the first one with a common cathode, the second one with a common grid) as a replacement for a pentode, and so the name may be assumed to be a contraction of "''casc''aded triodes having similar characteristics to a pent''ode''".〔"Cathode Ray", "The Cascode and its Advantages for Band III Reception", ''Wireless World'', vol. 61, p. 397 (August 1955).〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cascode」の詳細全文を読む スポンサード リンク
|