Audio Filters

The circuit as shown gives the bandpass operation the transfer function calculated from FBP(s) = where = 1 + s/Qo>0 + s2/w02. The cut-off frequency, 0, and the Q-factor are given by 0 = g/C and Q = gR/2 where g is the transconductance at room temperature. Interchanging the capacitor C with the resistor R at the input of the circuit high-pass operation is obtained. A low-pass filter is obtained by applying two parallel connections ctf R and C as shown in Fig. 2. The.....

Voice Scrambler/Descrambler

This circuit uses an NE602 as an inversion mixer. U2 is set to run at about 2.5 to 3.5 kHz. U3 drives a loudspe..

Voltage Controlled Filter SSM2044P

At this circuit the SSM2044 IC is used, a 4 pole voltage controlled filter designed for electronic music applications. On-chip voltage control of resonance allows direct and easy interfacing with programmers and controllers. The IC features extended control range, low noise, and high control rejection. The filter can also be used as a low distortion sinewave oscillator...

Tunable notch filter to suppress hum

This narrow-stop-band filter can be tuned by the pot to place the notch at any frequency from 45 to 90 Hz. It attenuates power-line hum or other unwanted signals by at least 30 dB..

Current-Driven Sallen Key Filter Circuit

The low-pass Sallen-Key filter is staple for designers because it contains few components (A). By redesigning the filter,..

Digitally tuned low power active filter

This constant gain, constant Q, variable frequency filter provides simultaneous low-pass, bandpass, and high-pass outputs with the component values shown, the center frequency will be 235 Hz and 23.5 Hz for high and low logic inputs. ..

Wideband two-pole high-pass filter

The circuit provides a 10MHz cutoff frequency. Resistor R3 ensures that the input capacitance of the amplifier does not interact with the filter response at the frequency of interest. ..

Programmable-attenuator

This circuit performs the function of dividing the input signal by a selected constant (1, 2, 4, 8, etc.). While T, Z, or L sections could be used in the input attenuator, this is not necessary since the amplifier loading is negligible and a constant input impedance is maintained. The circuit is thus much simpler and more accurate than the usual method of constructing a constant impedance ladder, and switching sections in and out with analog switches. ..

Twin-t-notch-filter

This filter is used to reject or block a frequency or band of frequencies. These filters are often designed into audio and instrumentation systems to eliminate a single frequency, such as 60Hz. Commercial grade components with 5%-10% tolerance produce a null depth of at least 30 to 40 dB. When a twinT network is combined with a TL081 op amp in a circuit, an active filter can be implemented. The added resistor capacitor network, R2 and C2, work effectively in parallel.....

Tunable Bandpass Filter

One of the difficulties in the design of higher-order tunable bandpass filters is achieving correct tracking of the..

Low-pass filter

This nonlinear, passive filter circuit rejects ripple (or unwanted but fairly steady-voltage) without appreciably affecting the rise time of a signal. The circuit works best when the signal level is considerably lower than the unwanted ripple, provided the ripple level is fairly constant..

Audio Compressor/Audio-Band Splitter

This 2-band compressor splits the audio into high and low frequencies and allows independent adjustmen..

Scanner Voice Squelch

This circuit detects the presence of audio (voice) on the output of a scanner. If the scanner stops on a "dead carrie..

Razor-sharp CW filter

The circuit consists of four stages of active bandpass filtering provided by two type-Âµ integrated-circuit dual op amps and includes a simple threshold detector (diodes Dl and D2) between stages 2 and 3 to reduce low-level background noise. Each of the four filter stages acts as a narrow bandpass filter with an audio bandpass centered at 750 Hz. ..

State-variable-active-filter

A generalized circuit diagram of the two-pole state-variable active filter is shown. The state-variable filter can be inverting or noninverting and can simultaneously provide three outputs: low-pass, bandpass, and high-pass. A notch filter can be realized by adding one summing op amp. In the state-variable filter circuit, one amplifier performs a summing function and the other two act as integrators. ..

Simple Audio Clipper/Limiter

For use with headphones, this circuit sets the audio clipping level via a 5-KOhmhm pot. This type of noise cli..

Variable-Frequency Audio Bp Filter Circuit

This variable-frequency, audio bandpass filter is built around two 741 op amps that are connected in cascade. Two 741 op amps are configured as identical RC active filters and are connected in cascade for better selectivity. The filter`s tuning range is from 500~Hz to 1500 Hz. The overall voltage gain is slightly greater than 1 and the filter`s is about 5, The circuit can handle input signals of 4 V peak-to-peak without being overdriven. The circuit`s input impedance is.....

Bandpass filter

The input signal is applied through R3 to the inverting input of the summing amplifier and the output is taken from the first integrator. The summing amplifier will maintain equal voltage at the inverting and non-inverting inputs. Defining 1/R1C1 as 1 and 1/R2C2 as u>2> th^ is now a convenient form to look at the center-frequency 0 and filter Q. ..

Noise limiter

This limiter improves signal-to-noise ratio. It is connected between the detector output and the audio input (if high impedance) or at some relatively high-impedance section between two audio stagesâ€”preferably the low level stages.D1 and D2 can be any diode having relatively low forward resistance and very high back resistance. The circuit is excellent for receivers having bandwidths down to 2 or 3 kHz...

Output-limiter

HA-5190 is rated for Â±5 V output swing, and saturates at Â±7 V. As with most op amps, recovery from output saturation is slow compared to the amplifier"s normal response time. Some form of limiting, either of the input signal or in the feedback path, is desirable if saturation might occur. ..