Lectures 27+28 - Lectures 27+28 A little more about power...

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Lectures 27+28 A little more about power Beginning amplifiers+op-amps
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DC power supplies + V1 - I 1 + V2 - V1 = 120V*cos(60Hz·2 π t) Transformer steps down voltage from wall voltage by N. Full wave rectifier converts to DC (see lecture 7+8), with drop of 2V TO = 1.4V (V TO = 0.7V) – When V2> Vout+2V TO , D2, D3 turn on, charge C – When V2< -Vout-2V TO , D1, D4 turn on, charge C – Otherwise, R discharges C So Vout ~ 120V/N-2V TO “ripple” set by R, C. Can power dc devices, charge batteries + Vout - D1 D2 D3 D4 -15 -10 -5 0 5 10 15 0 2 4 6 8 10 12 time V o lta g e V2 -V2 Vout
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Amplifiers Use amplifiers to make signals bigger Ideally, treat this as a voltage- controlled voltage source with gain Av. A sense for how this might be done: – Start with a voltage controlled conductance: this is a good model of: • Some transistors • Synapses – Load with big resistor+ battery Key points: – Battery voltage+ DC current needed – Always have an output impedance
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This note was uploaded on 11/21/2011 for the course ECE 2100 taught by Professor Kelley/seyler during the Spring '05 term at Cornell University (Engineering School).

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Lectures 27+28 - Lectures 27+28 A little more about power...

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