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IC electronic filters are frequency-selective circuits that consist of devices such resistors, capacitors, inductors, transistors, or operational amplifiers coupled with reactive components. IC electronic filters include active filters, passive filters crystal filters, digital filters, passive filters, SAW filters and others. Active filters are frequency-selective circuits that consist of active devices such as transistors, or operational amplifiers coupled with reactive components. Crystal filters are made of monolithic crystals such as synthetically-manufactured quartz, and use the piezoelectric effect to transmit signals from one set of electrodes to another. Digital filters are used with digital processors that perform numerical calculations on the sampled input signal in order to produce the required filtering function. Passive filters consist of passive electronic components such as resistors and capacitors, and do not produce any amplification of the input signal. SAW filters are IC electronic filters that are designed and manufactured using surface acoustic wave (SAW) technology.
Filter frequency response is an important specification to consider when selecting IC electronic filters. Choices include Bessel filters, Butterworth filters, Cauer or elliptic filters, and Chebyshev filters. Bessel filters are IC electronic filters that have a relatively flat passband and slow roll-off. The stopband is fairly monotonic or ripple-free. Butterworth filters provide a very flat response and almost no attenuation in the passband. The roll-off rate is somewhat slower than other filters. Cauer or elliptic filters provide the fastest roll-off for a given order (number of poles). Typically, the pass band and stop band have ripples. Chebyshev filters provide a very fast roll-off, but at the expense of a rippled pass band. Linear phase response filters preserve the phase characteristics of a signal by time-delaying the signal components equally.
Inputs and Outputs
IC electronic filters carry specifications for analog input channels and differential channels. The number of analog input channels is a maximum amount. A single-ended number is specified when single-ended inputs are available as twice the number of differential inputs. In some IC electronic filters, differential inputs are combinations of two single-ended inputs. Differential channels use the difference between two signals as an input. For example, if one reading is 4.93 V and the other reading is 5.16 V, the meaningful value is the 0.23 V difference between the two. This often applies to precision measurements where the difference between two low voltage inputs is small but critical.
BS EN 166100 - HARMONIZED SYSTEM OF QUALITY ASSESSMENT FOR ELECTRONIC COMPONENTS-SECTIONAL SPECIFICATION: SURFACE ACOUSTIC WAVE (SAW) FILTERS
BS EN 167000 - HARMONIZED SYSTEM OF QUALITY ASSESSMENT FOR ELECTRONIC COMPONENTS.GENERIC SPECIFICATION: PIEZOELECTRIC FILTERS
IEC 61261-1 - PIEZOELECTRIC CERAMIC FILTERS FOR USE IN ELECTRONIC EQUIPMENT- A SPECIFICATION IN THE IEC QUALITY ASSESSMENT SYSTEM FOR ELECTRONIC COMPONENTS (IECQ) PART 1: GENERIC SPECIFICATION- QUALIFICATION APPROVAL