ADA4075-2

Data Sheet

Rev. C | Page 20 of 24

LOW NOISE PARAMETRIC EQUALIZER

The circuit in Figure 69 is a reciprocal parametric equalizer

yielding ±20 dB of cut or boost with variable bandwidth and

frequency. The frequency control range is 6.9:1, with the geometric

mean center frequency conveniently occurring at the midpoint

of the potentiometer setting. The center frequency is equal to

48 Hz/Ct, where Ct is the value of C1 and C2 in microfarads.

The bandwidth control adjusts the Q from 0.9 to about 11. The

overall noise is setting dependent, but with all controls centered,

it is about −104 dBV in a 20 kHz bandwidth. Such a low noise

level can obviate the need for a bypass switch in many applications.

1/2

C2*

100

Ω

1k

Ω

BANDWIDTH

*THE CENTER FREQUENCY IS AFFECTED BY THE VALUE OF C1 AND C2

(SEE THE LOW NOISE PARAMETRIC EQUALIZER SECTION FOR MORE DETAILS).

1.3k

Ω

1/2

1/2

C1*

2.5k

Ω

620

Ω

2.5k

Ω

620

Ω

1.5k

Ω

1.3k

Ω

2.5k

Ω

1/2

ADA4075-2

ADA4075-2

ADA4075-2

ADA4075-2

6.2k

Ω

6.2k

Ω

47µF

5k

Ω

BOOST

CUT

1.5k

Ω

IN

OUT

2.5k

Ω

2.7k

Ω

620

Ω

FREQUENCY (GANGED POTENTIOMETER)

Figure 69. Low Noise Parametric Equalizer