Electronic apparatus for biological research electronicappara00dona Year: 1958 INDUCTANCES AND RESISTANCES SO for a wide pass-band we need L^, large. The upper turn-over frequency is at (Rl + Rs {r + R,) n' C02 = L,{1 - k^) so for a wide pass-band we need L^ small. Since the requirements for L^ conflict, we drop the notion of the actual turn-over frequencies and consider their ratio, since this gives us a measure of the band-width of the transformer. Oiq M-, (r + R^) + Rl + Rs n^ (1 k^^^^V + R.) n' In the special but important case where the generator is matched to the load Rs + Rl w and CO,
Electronic apparatus for biological research electronicappara00dona Year: 1958 INDUCTANCES AND RESISTANCES SO for a wide pass-band we need L^, large. The upper turn-over frequency is at (Rl + Rs {r + R,) n' C02 = L,{1 - k^) so for a wide pass-band we need L^ small. Since the requirements for L^ conflict, we drop the notion of the actual turn-over frequencies and consider their ratio, since this gives us a measure of the band-width of the transformer. Oiq M-, (r + R^) + Rl + Rs n^ (1 k^^^^V + R.) n' In the special but important case where the generator is matched to the load Rs + Rl w and CO, CO1 Rv + r 4 1 k^ Summarizing for signal transformers under matching conditions: (1) The actual load voltage is «Fout (because our Fout has referred to the primary of the ideal transformer) and in the pass-band this equals 0-5 n Ei^, provided the winding resistances are small. (2) The bottom end of the pass-band is at co = (r + Rp)l{2Lj,) (3) The pass-band extends over a 4/(1 — k^) fold range of frequencies. Danger—saturation The equations which have been deduced to describe transformer perfor- mance have been linear, in the sense that it appears that in either pulse or signal transformer the input voltage can be indefinitely increased, to produce a corresponding increase in output voltage. Figure For transformers having iron cores this is not so. The Hnear theory assumes the primary inductance L^ to be a constant, and the inductance expression contains the permeabihty of the iron, //, as a factor. If magneto-motive force is plotted against flux produced for a particular core, a curve results 70
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