Datasheet LTC1051, LTC1053 (Analog Devices) - 9

LTC1051/LTC1053
U U W U APPLICATIO S I FOR ATIO
2. If we arbitrarily accept that “aliasing” occurs when 4. When the frequency, fIN, of the input signal is less than output alias signals reach an amplitude of 0.01% or more fCLOCK, the alias signal(s) amplitude(s) directly scale with of the output signal, then: the approximate minimum the amplitude of the incoming signal. The output “signal to frequency of an AC input signal which will cause aliasing alias ratio” cannot be increased by just boosting the input is equal to the internal clock frequency multiplied by the signal amplitude. However, when the input AC signal square root of the op amp feedback factor. For instance, frequency well exceeds the clock frequency, the amplitude with closed-loop gain of –10, the feedback factor is 1/11 of the alias signals does not directly scale with the input and if fCLK = 2.6kHz, alias signals can be detected when amplitude. The “signal to alias ratio” increases when the the frequency of the input signal exceeds 750Hz to 800Hz output swings closely to the rails. (See Figure 5b and (Figure 5a). Figure 7.) It is important to note that the LTC1051/ LTC1053 op amps, under light loads (R 3. The number of alias signals increases when the input L ≥ 10k), swing closely to the supply rails without generating harmonic signal frequency increases (Figure 5b). distortion (Figure 8). B: MAG STATUS: PAUSED RANGE: 9dBV RMS: 25 13dBV 10k 5V 83.5dB 15dB 0.1µF /DIV 10k – 1/2 LTC1051 + 50pF –107 0.1 CENTER: 2 625Hz BW: 19.097Hz SPAN: 2 000Hz µF VIN = 10kHz X: 2535Hz Y: – 74.16dBV 8VP-P – 5V 1051/53 F05a NOTE: THE fCLK – fIN = 85Hz ALIAS FREQUENCY IS 95dB 2f f CLK – fIN IN = 2.685kHz f DOWN FROM THE OUTPUT LEVEL CLK
Figure 6a. Output Voltage Spectrum of 1/2 LTC1051 Operating as a Unity-Gain Inverting Amplifier. VS =
±
5V, RL = 10k, CL = 50pF, VIN = 8VP-P, 2.685kHz
B: MAG STATUS: PAUSED RANGE: 9dBV RMS: 50 13dBV 15dB 80dB 15dB /DIV –107 CENTER: 10 000Hz BW: 95.485Hz SPAN: 10 000Hz X: 10000Hz Y: 7.98dBV 1kHz 5fCLK – fIN fIN – 2fCLK 2 • f f f CLK IN – fCLK IN = 10kHz 6fCLK – fIN NOTE: ALL ALIAS FREQUENCY 80dB TO 84dB DOWN FROM OUTPUT
Figure 6b. Output Voltage Spectrum of 1/2 LTC1051 Operating as a Unity-Gain Inverting Amplifier. VS =
±
5V, RL = 10k, CL = 50pF, VIN = 8VP-P, 10kHz
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