低通滤波器的应用考虑

　　Description

　　The LTC®1062 is a versatile， DC accurate， instrumentation lowpass fi lter with gain and phase that closely approximate a 5th order Butterworth fi lter. The LTC1062 is quite different from presently available lowpass switched-capacitor fi lters because it uses an external （R， C） to isolate the IC from the input signal DC path， thus providing DC accuracy. Figure 1 illustrates the architecture of the circuit. The output voltage is sensed through an internal buffer， then applied to an internal switched-capacitor network which drives the bottom plate of an external capacitor to form an input-to-output 5th order lowpass fi lter. The input and output appear across an external resistor and the IC part of the overall fi lter handles only the AC path of the signal. A buffered output is also provided （Figure 1） and its maximum guaranteed offset voltage over temperature is 20mV. Typically the buffered output offset is 0mV to 5mV and drift is 1μV/°C. As will be explained later， the use of an input （R， C） provides other advantages， namely lower noise and antialiasing