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The signal conditioner -- changes the voltage

The signal conditioner -- changes the voltage. Amplify Attenuate Filter. + V n _. + V o -. +V p -. Operational Amplifiers -- a.k.a. “ op-amps ”. Limits of Op-Amp Performance First consider the characteristics of an ideal op-amp: internal (“open loop”) gain = ¥

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The signal conditioner -- changes the voltage

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  1. The signal conditioner -- changes the voltage Amplify Attenuate Filter

  2. + Vn _ + Vo - +Vp - Operational Amplifiers -- a.k.a. “op-amps” • Limits of Op-Amp Performance • First consider the characteristics of an ideal op-amp: • internal (“open loop”) gain = ¥ • bandwidth = ¥ (max. operation freq.) • input resistance = ¥ (input impedance) • output resistance = 0 (output impedance) • Vo = 0 when Vn = Vp V+ V-

  3. Limits of Op-Amp Performance • Real op-amps can only approximate these ideal specifications: • Realinternal (“open loop”) gain = 104 to 109 • Realbandwidth depends on gain (1kHz to 1 MHz) (max. operation freq.) • Realinput resistance = 105 to 1012W (input impedance) • Realoutput resistance = 25 to 100 W (output impedance)

  4. R2 = 99000W R1 = 1000W + Vo - +Vi - Noninverting Amplifier Using an Op-Amp • Example:

  5. Noninverting Amplifier Using an Op-Amp • What happens to the output voltage of this amplifier as the input voltage is increased? What is happening?

  6. Output Saturation • If Vi is high enough so that Vo = G Vi approaches the power supply voltage, further increases in Vi will not increase the output. • This situation is called output saturation. • Output saturation typically occurs when the output voltage reaches a magnitude about 1 or 2 volts below the power supply voltage. • For example, if the power supply provides ±15 volts to run the op-amp, saturation will occur when the output reaches about ±13 volts.

  7. Frequency Response • The gain that we calculate for an amplifier circuit that contains an op-amp really is only correct if the input signal is a dc voltage, or a low frequency (slowly oscillating) ac voltage. • If the frequency of the input voltage is increased, the amplifier gain will eventually be seen to decrease.

  8. Frequency Response For example: The gain of the complete noninverting amplifier circuit and the internal gain of the op-amp will both decrease if the frequency of the input voltage is made high enough.

  9. Frequency Response Recall that the gain can also be expressed in decibels.

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