Amplifiers – With semiconductor amplifying device – Including gain control means
Patent
1979-03-16
1981-06-23
Mullins, James B.
Amplifiers
With semiconductor amplifying device
Including gain control means
H03G 330, H03G 924
Patent
active
042753627
ABSTRACT:
A gain controlled amplifier is provided which is capable of handling a wide range of input signal levels without the need for input signal attenuation. A transistor is arranged in a common emitter amplifier configuration and includes a PIN diode as a controllable impedance in the emitter circuit. An input signal and a gain control voltage are applied at the base of the transistor. As the input signal level increases, the gain control voltage is decreased, causing an increase in the substantially resistive impedance of the PIN diode, which bears a constant relationship to the decreasing gain control voltage (i.e., a linear relationship on a semilog plot). The gain of the transistor amplifier is thereby reduced. At high input signal levels, the impedance of the PIN diode comprises a large resistive component in parallel with a large reactive (i.e., small capacitive) component at the emitter of the transistor, thereby affording substantial gain reduction. A novel PIN diode is provided for use in such a gain controlled amplifier, comprising a first localized region of high resistivity semiconductor material having a substantially planar surface. Second and third localized regions of one type conductivity are located in the high resistivity region adjacent to the surface. A fourth localized region of opposite type conductivity is located in the high resistivity region adjacent to the surface and intermediate the second and third localized regions, and is separated laterally from the first and second regions by zones of the high resistivity material.
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Badal, "Variable Gain Amplifier for AGC", IBM Technical Disclosure Bulletin, vol. 5, No. 9, Feb. 1963, p. 32.
Brinton Yorks, Jr. W.
Meagher William H.
Mullins James B.
RCA Corporation
Whitacre Eugene M.
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