. The Bell System technical journal . sible to use miniature com-ponents thereby gaining at least an order of magnitude in the size andweight of structure. 340 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1951 5 ° z 1^ ^-^ ^if) _i H a: Lij CO z 1 { ■\\ **v^^ if11/ / \ \ ^ ^ I M WITHTRANSISTORS \ _ WITHOUT TRANSISTORS 1 \ 1 1 \ \ V y, V y I \ .-x FREQUENCY IN KILOCYCLES PER SECOND Fig. 8 — Resistance compensation of multi-section filter. Series Negative Resistance For satisfactory p
. The Bell System technical journal . sible to use miniature com-ponents thereby gaining at least an order of magnitude in the size andweight of structure. 340 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1951 5 ° z 1^ ^-^ ^if) _i H a: Lij CO z 1 { ■\\ **v^^ if11/ / \ \ ^ ^ I M WITHTRANSISTORS \ _ WITHOUT TRANSISTORS 1 \ 1 1 \ \ V y, V y I \ .-x FREQUENCY IN KILOCYCLES PER SECOND Fig. 8 — Resistance compensation of multi-section filter. Series Negative Resistance For satisfactory performance in many applications a series resonantcircuit should approach zero impedance at the resonant frequency. Toreduce the residual dissipation in an ordinary tuned circuit a seriesnegative resistance, consisting of two transistors, can be used. Thistechnique is illustrated in Fig. 11 which shows how a purely reactiveshunt branch can be achieved in either an /??-derivcd low pass filter ora confluent band elimination Fig. 9 — 98-kc active channel filter. 4036 32 If)-Jlij (0 28O lU az24 ID in 3 20 zo ^ 16 lU i/> Z 128 40 \ /^ \ 11 V / vJ / / \ / V / 95 96 97 98 99 100 101 FREQUENCY IN KILOCYCLES PER SECOND Fig. 10 — Active channel 342 THE BELL SYSTEM TECHNICAL JOURNAL, MARCH 1954 II. ELIMINATION OF INDUCTANCE In the practical realization of frequency selective networks it is some-times awkward, difficult, or even impossible to make effective use of coilsas inductive elements. This is true, because of severe limitations on space,exacting tolerances on undesired modulation, or necessity for operationat extremely low frecjuencies. It has been well known for some time that inductive elements can beeliminated without restricting the repertoire of the network designerprovided he is willing to purchase this freedom by introducing activeelements to supply gain. It can be easily shown that the transmission through a high gain feed-back amplifier is pro
Size: 1810px × 1381px
Photo credit: © Reading Room 2020 / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
