|
|
|
|
|
|
|
|
|
|
|
|
|
|
Active Filters:
Low Pass
|
3KHz LOW PASS FILTER PLUS AUDIO AMP
This circuit uses a switched capacitor filter IC from
National Semiconductor to filter signals with
frequencies higher than the 3KHz needed for voice audio. The
schematic includes an audio amplifier
that is designed to drive a standard audio head phone. The
circuit is described in more detail in the receiver section of Dave Johnson's
Handbook of Optical Through the Air Communications.
(this link is off-site) |
|
AUDIO AMP + 3KHz FILTER
This circuit is the audio amp section for a complete
optical transmitter. The circuit amplifies and
filters the voice audio signals from an electrets microphone.
The circuit is described in more detail in
the transmitter circuit section of
Dave Johnson's
Handbook of Optical Through the Air
Communications. (this link is off-site) |
|
ELECTRIC FIELD DISTURBANCE MONITOR
This schematic is the power supply and front-end sections of
the field monitor that is discussed in more detail at
Electric Field Disturbance Monitor. The system can
detect human and animal motion by the electric fields they
disturb. |
|
LOW PASS ACTIVE FILTER DESIGN COLLECTION
This is a collection of inverting and non-inverting active
low pass filter circuits. I included one, two, three, four
and six pole filter circuits. You can change the component
value ratios shown, to achieve any frequency cut-off you may
need. The circuit does not specify an operational
amplifier. The circuits should be used to select the needed
resistor and capacitor components for a particular frequency
knee and roll-off slope. |
|
Active 2nd Order Filters: |
|
Active Filter has Wideband Tuning Range: EDN-Design
Ideas |
|
|
|
Adjustable Filter Provides Lowpass Response: EDN-Design
Ideas PDF contains multiple circuits - scroll
to find the one of interest |
|
Basic Introduction to Filters: application notes
on active, passive and switched capacitor filters,
document in PDF format |
|
Butterworth Filters: |
|
Chebyshe Volt / Butterworth Filters:
|
|
Chebyshe Volt Bandpass Filter:
|
|
DC Accurate, Active RC Lowpass Filter:
|
|
Low Pass Active Filter: |
|
Lowpass filter discriminates step input from noise
: EDN-Design Ideas / Numerous
applications exist in industry, particularly with
control systems, in which it is desirable to remove
all but the lowest frequency components from a
signal to effectively yield a dc voltage. This
voltage may, for example, serve as a setpoint to a
PID controller in a process-control or an HVAC
application, in which the cable that is carrying the
analog signal is exposed to a wide spectr......
|
|
Lowpass filter uses only two values: EDN -
Design Ideas / In recent years,
image-parameter design of LC filters has received
new consideration (references 1 and 2). The
composite lowpass filter uses interior constant-k
full sections terminated by m-derived half-sections.
For best passband response, you usually select m to
equal 0.6. However, m=0.5 can still give useful
filter performance while reducing the number of
component values.. |
|
Single resistor tunes lowpass filter : EDN-Design
Ideas / Any tunable, second-order, active RC-filter
section requires at least two thoroughly matched
variable resistors. But the lowpass implementation
in Figure 1 provides for wide-range cutoff-frequency
control using only a single variable resistor, R. In
addition to the resistor, this filter comprises an
operational amplifier, IC2, which serves as a
unity-gain buffer; two capacitors, C1 and C2; ...... |
|
Single Supply Twin T Butterworth Low Pass Filter:
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
