Datenblatt-Suchmaschine für elektronische Bauteile |
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AD883B Datenblatt(PDF) 8 Page - Analog Devices |
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AD883B Datenblatt(HTML) 8 Page - Analog Devices |
8 / 12 page AD549 REV. A –8– positive input terminal. The amplifier’s input offset voltage drift with temperature is not affected. However, variation of the power supply voltages will cause offset shifts. Figure 31. Alternate Offset Null Circuit for Inverter AC RESPONSE WITH HIGH VALUE SOURCE AND FEEDBACK RESISTANCE Source and feedback resistances greater than 100 k Ω will mag- nify the effect of input capacitances (stray and inherent to the AD549) on the ac behavior of the circuit. The effects of common-mode and differential input capacitances should be taken into account since the circuit’s bandwidth and stability can be adversely affected. Figure 32. Follower Pulse Response from 1 M Ω Source Resistance, Case Not Bootstrapped Figure 33. Follower Pulse Response from 1 M Ω Source Resistance, Case Bootstrapped In a follower, the source resistance and input common-mode capacitance form a pole that limits the bandwidth to 1/2 π R SCS. Bootstrapping the metal case by connecting Pin 8 to the output minimizes capacitance due to the package. Figures 32 and 33 show the follower pulse response from a 1 M Ω source resistance with and without the package connected to the output. Typical common-mode input capacitance for the AD549 is 0.8 pF. In an inverting configuration, the differential input capacitance forms a pole in the circuit’s loop transmission. This can create peaking in the ac response and possible instability. A feedback capacitance can be used to stabilize the circuit. The inverter pulse response with RF and RS equal to 1 M Ω appears in Figure 34. Figure 35 shows the response of the same circuit with a I pF feedback capacitance. Typical differential input capacitance for the AD549 is 1 pF. COMMON-MODE INPUT VOLTAGE OVERLOAD The rated common-mode input voltage range of the AD549 is from 3 V less than the positive supply voltage to 5 V greater than the negative supply voltage. Exceeding this range will de- grade the amplifier’s CMRR. Driving the common-mode voltage above the positive supply will cause the amplifier’s output to saturate at the upper limit of output voltage. Recovery time is typically 2 µs after the input has been returned to within the nor- mal operating range. Driving the input common-mode voltage within 1 V of the negative supply causes phase reversal of the output signal. In this case, normal operation is typically resumed within 0.5 µs of the input voltage returning within range. Figure 34. Inverter Pulse Response with 1 M Ω Source and Feedback Resistance Figure 35. Inverter Pulse Response with 1 M Ω Source and Feedback Resistance, 1 pF Feedback Capacitance DIFFERENTIAL INPUT VOLTAGE OVERLOAD A plot of the AD549’s input currents versus differential input voltage (defined as VIN+ –VIN–) appears in Figure 36. The input current at either terminal stays below a few hundred femtoamps until one input terminal is forced higher than 1 V to 1.5 V above the other terminal. Under these conditions, the input current limits at 30 µA. |
Ähnliche Teilenummer - AD883B |
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Ähnliche Beschreibung - AD883B |
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