Datasheet LTC1047 (Analog Devices) - 6

LTC1047
U U W U APPLICATIO S I FOR ATIO Input Considerations Aliasing
Frequently circuits built with parts as precise as the Like all sampled data systems, the LTC1047 will alias input LTC1047 show errors at the output far greater than the signals near its internal sampling frequency. The design designer expects. Rarely is the problem the op amp; more includes internal circuitry to minimize this effect; as a often the surrounding circuitry is causing errors several result, most applications do not exhibit aliasing problems. orders of magnitude greater than those due to the LTC1047. For a complete discussion of the correction circuitry and Such obscure effects as leakage between pins, due to aliasing behavior, refer to the LTC1051/LTC1053 data residual solder flux and thermocouple effects between the sheet. tin/lead solder and the copper PC board traces, can overwhelm the pA-level bias currents and the µV-level
Single Supply Operation
offset of the LTC1047. For a more complete description of The LTC1047 is compatible with all single supply these types of problems (and some advice on avoiding applications. It has an input common mode range which them), see the LTC1051/LTC1053 data sheet. includes V–, and an output which will swing within millivolts of the negative power supply. The LTC1047 is
Input Capacitance
guaranteed functional down to 4.75V total supply, The LTC1047 has approximately 12pF of capacitance at allowing it to run from minimum TTL voltage all the way up each input pin. This will react with large series resistors to to 16V. See the Typical Applications section for examples form a pole at the input, degrading the LTC1047's phase of single supply operation. margin. The problem is especially common with micropower parts like the LTC1047 because high value resistors are often used to minimize power dissipation. As a rule of thumb, bypass feedback resistors larger than 7k with a 20pF capacitor to minimize this effect. 1047fa 6