Operational Amplifier Applications Unit 4 – High Pass Filter
UNIT 4 – HIGH PASS FILTER
UNIT OBJECTIVE
At the completion of this unit, you will be able to determine the operating characteristics of high
pass filters by analyzing first order and second order op amp filter circuits. You will verify your
results with an oscilloscope.
UNIT FUNDAMENTALS
A high pass filter is a circuit that allows frequencies above a specified limit to pass but
attenuates all frequencies below the limit.
For the ideal high pass filter characteristics shown, the point at which input signals begin to pass
to the output is called the corner frequency (fc).
The range of frequencies passed by the filter (above fc) is the passband.
The range of frequencies blocked by the filter is the stopband.
The response curve for a practical high pass filter shows a more gradual transition from stopband
to passband.
The corner frequency (fc) is the point at which the output voltage is at 70.7% of the passband
level, which corresponds to a -3 dB attenuation. This point is also called the 3 dB down point.