Slew Rate Op Amps Process Large Signals with Low Distortion at High Frequencies
نویسنده
چکیده
Introduction The LT1818 and LT1819 are low distortion single and dual operational amplifiers that offer 400MHz gain bandwidth product and 2500V/μs slew rate. The parts operate with supplies from ±2V to ±6V and draw a typical supply current of only 9mA per amplifier. The amplifiers can drive 100Ω loads with a low distortion of –85dBc relative to a 5MHz, 2VP–P signal. In single 5V supply applications, the output swings to 0.8V from either supply rail with a 500Ω load (to 2.5V), and to 1.0V with a 100Ω load. The output current drive capability is typically 70mA. The low distortion and good output drive capability, combined with the 6nV/√Hz input voltage noise, make the LT1818/LT1819 an ideal choice for a wide variety of applications. The LT1818 and LT1819 are available in space saving packages: the LT1818 single op amp in an SOT23-5; the LT1819 dual op amp in an 8-lead MSOP. Both parts are also available in an easy to use 8-lead SOIC. All parts are fully specified at ±5V and single 5V supplies, and are available in commercial and industrial temperature grades. Table 1 summarizes the performance specifications of the LT1818 and LT1819. Fast Slew Rate Preserves High Bandwidth for Large Signals The LT1818/LT1819 amplifiers exhibit an ultrafast slew rate of 2500V/ μs in a gain of +1 and 1800V/μs in a gain of –1. The importance of a high slew rate is demonstrated by comparing the large signal dynamic response of amplifiers with similar bandwidths but differing slew rates. We compared the LT1818 to a competitor’s amplifier, which has a wider, 625MHz bandwidth, but only a 400V/μs slew rate. Figure 1 shows a test circuit for a device configured in an inverting gain (AV = –1). Figures 2a and 2b show the step response to a 20MHz, ±4V input pulse. The 3.5ns rise/fall time of the LT1818 (consistent with a 1800V/μs slew rate) preserves the 20MHz step very well. The lower slew rate amplifier, in contrast, is only barely fast enough to transmit the waveform, 2500V/μs Slew Rate Op Amps Process Large Signals with Low Distortion at High Frequencies by Kris Lokere and Glen Brisebois
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