Datasheet

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LMH6629

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SNOSB18G –APRIL 2010–REVISED MARCH 2013

For higher selectivity, use high C values; for wider bandwidth, use high L values, while keeping the product of L

and C values the same to keep f

intact. The integrator’s -3dB roll-off is set by

(12)

(13)

the integrator and the bandpass filter frequency interaction is minimized so that the operating frequencies of each

can be set independently. Lowering the value of R2 increases the bandpass gain (boost) without affecting the

integrator frequencies. With the LMH6629’s wide Gain Bandwidth (4GHz), the center frequency could be

adjusted higher without worries about loop gain limitation. This increases flexibility in tuning the circuit.

Figure 69. Low-Noise Magnetic Media Equalizer

Figure 70. Equalizer Frequency Response

LOW-NOISE SINGLE ENDED TO DIFFERENTIAL CONVERTER / DRIVER

Many high-resolution data converters (ADC’s) require a differential input driver. In order to preserve the ADC’s

dynamic range, the analog input driver must have a noise floor which is lower than the ADC’s noise floor. For an

ADC with N bits, the quantization Signal-to-noise ratio (SNR) is 6.02* N + 1.76 in dB. For example, a 12-bit ADC

has a SNR of 74 dB (= 5000 V/V). Assuming a full-scale differential input of 2Vpp (0.707 V_RMS), the

quantization noise referred to the ADC’s input is ~140 μV_RMS (= 0.707 V_RMS / 5000 V/V) over the bandwidth

“visible” to the ADC. Assuming an ADC input bandwidth of 20 MHz, this translates to just 25 nV/RtHz (=

141µV_RMS / SQRT(20 MHz * π/2)) noise density at the output of the driver. Using an amplifier to form the

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