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 | Symmetrical parallel RC Multiple-T Frequency Combinations
Author : Sundarababu, A.;Balasubramanian, N.
Source : Defence Science Journal ; Vol:16(1) ; 1966 ; pp 7-12
Subject : 621.38 Electronics
Keywords : Communication;Frequency;Resistance and capacitance arms;Communication networks
Abstract : For a given number of resistance alms n, and capacitance arms nc in a symmetrical parallel RC multiple-T, it is possible to know the maximum number of dissimilar resonant frequency combinations theoretically from a formula derived using a combinational technique. Verification of the results is done by counting the number of dissimilar frequencies for the ratio nr/ nc. WM=WD (nrnc)1/2 and also from frequencies practically determined. The technique common to both these methods is the combinatorial nne as used in deriving Euler's Totient function in the theory of numbers. |
| | On noise figures in transistor audio amplifiers
Author : Rao, E. Bhagiratha
Source : Defence Science Journal ; Vol:12(3) ; 1962 ; pp 1-10
Subject : 534.8 Acoustics
Keywords : Frequency ;Collector voltage ;Collector current ;Emitter current ;Input impedance
Abstract : The noise figures of two general purpose transistors of Philips and Hitachi (Japanese) make have been determined under identical experimental conditions with a view to see whether they differ in their noise properties. The variation of noise figure of Philips as well as Hitachi transistors with (i) frequency (ii) collector voltage (iii) collector current (iv) emitter current (v) input impedance have been investigated. It was concluded that Philips and Hitachi transistors do not differ much in their noise properties, when operated under identical conditions. For both the transistors the noise figure increase with collector voltage, collector current and emitter current. Increasing input impedance of either of the transistors increases the noise figure when the input impedance exceeds two thousand ohms. For both transistors the noise figure decrease with frequency, then remains constant over a small frequency band and finally increases slowly with frequency. |
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