Electronics III
Exercise4
Filters
Concepts:
effect of frequency on Capacitive Reactance: As the frequency increases, Xc
decreases.
Concepts: What is the basic operation of filters?
Concepts: Passive Filters
Low pass filter
Concepts: Passive Filters
High pass filter
Concepts: Passive Filters
Band pass filter
Concepts: Terminology
 The critical frequency, (also called the cutoff frequency) defines the end of the
passband and is normally specified at the point where the response drops
(70.7%) from the passband response.
Filters that use op-amps as the active element provide several advantages over
passive filters (R, L, and C elements only). The op-amp provides gain, so the signal
is not attenuated as it passes through the filter. The high input impedance of the
op-amp prevents excessive loading of the driving source, and the low output
impedance of the op-amp prevents the filter from being affected by the load that
it is driving. Active filters are also easy to adjust over a wide frequency range
without altering the desired response.
Concepts: Active Filters
Low pass filter
Non-Inverting case
Inverting case
Concepts: Active Filters
High pass filter
Non-Inverting case
Inverting case
Concepts: Active Filters
Band pass filter
Non-Inverting case
Inverting case
Q1: Design a non-inverting active low pass filter circuit that has a gain of 10 at
low frequencies, a high frequency cut-off or corner frequency of 159Hz and an
input impedance of 10KΩ.
Q2 A first order non-inverting active high pass filter has a pass band gain of 2 and
a cut-off corner frequency of 1kHz. If the input capacitor has a value of 10nF,
calculate the value of the cut-off frequency determining resistor and the gain
resistors in the feedback network.
Q3: In the figs below. determine(a) the filter type ,(b) the corner frequency(s),
and (c) the DC gain