OpAmp-tutorial-1

Current vcis transresistance amplifier vcis current

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Unformatted text preview: mA 10 vo = -iFRF = 10 mA * 200 = 2 V rm = vo/iin = RF = 200 200 Find: iF , vo and rm Find: Power Bandwidth Power The maximum frequency at which a sinusoidal output signal can be The produced without causing distortion in the signal. produced The power bandwidth, BWp is determined using the desired output signal amplitude and the the slew rate ( see next slide) output specifications of the op amp. specifications BWp = SR 2π Vo(max) SR = 2π fVo(max) where SR is the slew rate Example: Given: Vo(max) = 12 V and SR = 500 kV/s Find: BWp Solution: BW p = 500 kV/s = 6.63 kHz 500 2π * 1 2 V Slew Rate Slew A limitation of the maximum possible rate of change of the limitation output of an operational amplifier. output As seen on the previous slide, As This is derived from: This SR = 2π fVo(max) SR = vo/ tmax SR f is the frequency in Hz Hz Slew Rate is independent of the Slew closed-loop gain of the op amp. closed-loop Example: Given: SR = 500 kV/s and vo = 12 V (Vo(max) = 12V) Given: 12 Find: The t and f. Find: Solution: t = vo / SR = (10 V) / (5x105 V/s) = 2x10-5 s Solution: f = SR / 2π Vo(max) = (5x105 V/s) / (2π * 12) = 6,630 Hz SR Slew Rate Distortion Slew v desired output desired waveform waveform SR = v/ t = m (slope) SR v actual output actual because of slew rate limitation limitation t t The picture above shows exactly what happens when the The slew rate limitations are not met and the output of the operational amplifier is distorted. operational Noise Gain Noise The noise gain of an amplifier is independent of the amplifiers The configuration (inverting or noninverting) configuration The noise gain is given by the formula: AN = R1 + RF R1 Example 1: Given a noninverting amplifier with the resistance Example values, R1 = 2 k and RF = 200 k Find: The noise gain. Find: AN = 2 k + 200 k = 101 2 k Note: For the noninverting amplifier AN = AV noninverting Example 2: Given an inverting amplifier with the resistance Example values, R1 = 2 k and RF = 20 k Find: The noise gain. A N = 2 k + 2 0 k = 1 2 2 k Note: For the inverting amplifier AN > AV inverting Gain-Bandwidth Product Gain-Bandwidth In most operational amplifiers, the open-loop gain begins In droppin...
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